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Lightest AR-15 scope mount?

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/09/2011 at 13:56
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I went ahead and uploaded a pic anyway.  Here is the GGG mount with Mark's (that he graciously loaned me for a few months) SS 3-9, showing that it will easily accommodate a much larger objective.  Of course, it's only available in all black; I had mine, along with the aluminum parts of my entire rifle, camo anodized.  At the time, the pic wasn't intended to focus on the mounts, so I don't have a pic of the cam lever side of the mount.




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+1 on GG&G...Level as well always a plus...
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/17/2011 at 00:40
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My intention was never to make the lightest avaible scopemount for AR 15, but the strongest.
So in order to keep it strong we use 7075 aluminium that is very much stronger than the more common 6061 and 6082 (over 50% stronger).
 
As the comment comes up that this is overpriced I choosed to reply to that with some pictures and explanations here.
As the mounting system is a primary a military/duty mounting system, the system thinking was very central and important.
Therefor there is 7-8 interfaces all over the mount where various assesories can be mounted.
The idea about cutting the rings in .45 degrees is to increase the visiability for the user of the knobs on the scope so he easyer and faster kan do necesarry adjustments.
We try to make the mount as ligth as possible, but weight are a secondary feature after the others features such as strength, repatability and versatility and userfriendlyness.
 
I prefer to not look as this as a mount, but a mounting system as it offers possibilitys no other mounts offers.
Machined out of one piece, not several held together by screws.
 
 
Shown here with Aimpoint T1 piggybacked 3 o'clock on the mount.
The gun can just be rotated and you will look right into the aimpoint instead of the scope.
 
 
This is a picture showing our previous model of AR mounts.
Current model is shorter to accomodate BUIS and have only one recoillug.
The contact surface have been limited to increase the repetability against the picatinny rail.
Lightning cuts have been made whereever possible.
 
 
HK417 setup with Hensoldt 4-16, aimpoint and PEQ15.
And advantage of mounting the laser on the scopemount is that its unaffected by the preasure applied on the forend while and will thus better keep it's POI.
 
 
Rings cut in 45 degree to give the shooter the easyest and fastest view of his knobs.
Here with T1 on the top and PEQ15 to the right.
 
 
All rings are groved on the inside to get the best grip on the scope and to give place for gluing for those who like that. All mounts are marked clearly with direction and tilt, as well as the modelname.
All parts in the system have their own number engraved into them
 
Also separate rings are availible shown here with spacer and direct inferface for doctor red dot.
 
 
The Wedge from the side is a tool used to level the scope.
The mount have a 10 degree cut and the wedge is 10degree.
That way the scopemounting is very easy.
Also please notice the level on the rear of the mount, always there, always well protected.
 
So is it overpriced?
For the user who needs/wants some of those features that are built in, the price will likely be pretty much the same whatever bought.
A strong ordinary scopemount, a level, a system for a back upred dot sight and we are probably very close in price to what we sell those mounts for.
 
For the user who not needs the features, then is this product likely overqualified and thus expensive. Maybe like buying a zeiss 6-24 when hunting deer in short distances.
 
Best Regards Håkan Spuhr
 
 
 
 
 
 
 
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/23/2011 at 18:40
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First I want to say I'm not one to talk down another's products.  By all reports the Spuhr mounts are very nice indeed and plenty strong.  However, in order to better inform the customer I want to clear up some misconceptions that are being developed.

First, in my years as a Mechanical Engineer, one thing I've noticed is how non-technical people seem to place more importance on material choices than they may deserve.  The material choice is of course very important to the overall strength of the end product, but it's only one of many important factors.  In parts where the design and geometry can vary wildly, it is often far from the most important factor.  It doesn't take a horrible design, just a few critical mistakes--mistakes most wouldn't notice--to turn a very strong block of titanium or steel in to a very weak part.

For just one simple example that everybody can visualize as it applies here, let's consider the foot area of a mount/ring that grabs the picatinny rail opposite the clamp--the exact area we have seen several brands of 7075-T6 aluminum rings fail.  Here you have a critical cross section in bending.  If two parts have identical geometry and one is made from 7075-T6 and the other is made from 6061-T6, the 7075 part is nearly twice as strong for an ultimate static load.

But since the cross sectional moment of inertia is proportional to the cube of the thickness, if one increases the thickness of the 6061 part by only 30% you cut the peak stress levels nearly in half.  So now the 6061 part is just as strong for an ultimate load as the 7075 part with a thickness increase so small many wouldn't notice without it being pointed out to them.

What else has changed?  The 6061 part is twice as stiff.  This is important for return to zero which we'll discuss more later.

What else has changed?  The 6061 part has 10 TIMES the fatigue life.  That's right, roughly 10 TIMES the fatigue life.  There's more to a part's design than the ultimate tensile strength of the material.  Just because one can run 7075-T6 at high stress levels without yielding it, doesn't mean one always should if fatigue life is a concern.  

Now imagine if the 6061 part was made 75% thicker?  Twice as thick?  It would be so much stronger in every way it's not even a remotely fair comparison.   And that particular thin cross section can be thickened a great amount with little impact to the overall size and weight of the part.  That's just one example.

Of course one could make the same change to the 7075 part and it would be stronger yet.  But if it was strong enough before, now you're wasting your customers' money by charging them for a more expensive material which is not needed for the application.  If designed for stiffness and fatigue life means you come up with a thickness where 6061 provides way more ultimate strength than needed, you gain nothing by changing to 7075 except for the advertising.

One doesn't need to be an Engineer to understand these concepts.  I think most of the well informed customers, upon hearing it claimed that one part is stronger than another based solely upon the material choice will recognize that as advertising--which may or may not have basis in fact for parts with different geometry (quite often a whole lot more than 30% thickness difference).  

It's different when the geometry is fixed.  For example with a Picatinny Rail one can't simply make the lugs thicker, etc, because then it will be out of spec.  For a part like that one can reasonably assume that a titanium rail will be stronger and stiffer than an aluminum rail and so on if comparing like designs (full width slots, etc).

Next, the issue of return to zero.  There seems to be a myth that got started a year or so ago that less contact area somehow results in better return to zero performance.  This myth relies upon a spec or two of dirt being in the contact area of one mount, messing it up, where another mount which doesn't have that particular contact area can't be messed up by that particular convenient particle of dirt.  It follows with that logic the best return to zero mounts/rings are those with no contact area at all--the ones held in position above the rail by the power of The Force.

Seriously, since the only place dirt tends to collect on picatinny rails is the bottom of the slots--and I don't know of any mount or ring that contacts there--it's quite far-fetched.  The top surface and the bottom of the sides of the rail, where most of the contact occurs, are quickly and easily wiped in the odd case of somebody having placed a pile of dirt there but usually remain quite bare.

What less contact area WILL mean, without fail, inescapably and without requiring a convenient piece of dirt for the assist, is higher bearing stress levels.  This means more deflection when the mount is torqued to the rail.  When less contact area means that contact is supported by shorter lengths of cross section (not to mention thinner) as in the foot example above, that means many more times as much deflection under the same clamp load from the clamp on the other side.

The magnitude of deflection is important because it determines the scope's final position above the rail.  A large amount of deflection can be felt when torquing the mount/rings to the rail--how quickly the fasteners go from finger tight to torqued.  Of course that also depends upon the rail material and the side clamp design.

A large deflection wouldn't be a problem if one can ensure the exact same amount of clamp load is applied to the clamp every time--the scope will always be in the same place.  If customers always used pro quality, often calibrated torque wrenches, and meticulously cleaned and lubricated the fasteners with ARP Ultra-Torque™ moly lube (if you build race engines, you'll know what that is), you could count on pretty close to the same amount of preload on the clamp every time.

Of course in the real world that won't happen.  Even if the customer is using an accurate torque wrench, the fasteners may be dirty, clean, wet or dry…the anodize underneath the heads won't look the same after 5 years of use as it did the first time so they'll make for a different amount of friction, etc.  In other words, the preload will vary even when the customer is trying.  

If the total amount of deflection under this preload is greatly reduced, then the variation of the magnitude of the deflection with variations in preload will also be greatly reduced--in other words the scope goes more closely back to the same place every time.  That's why stiffness is an asset for repeatedly returning to zero.  And in my case I wanted the customers to have satisfactory results using no torque wrench at all.  Of course it's always better to use one but a mounting system that will be "close enough" in a pinch without has an advantage.  

Much the same applies to increasing the bearing area of the recoil lugs, although this will be most noticeable on heavy recoiling rifles--particularly those with an aluminum rail.  With such rifles, one often notices upon re-installation of the scope the first shot is "out of the group" while successive shots land back at the original zero from before the scope was removed.  This is due to the mounting system flexing together, "taking a set" during the first shot.  It can also be exacerbated when a scope is moved from rifle to rifle, rail to rail.  Even quality picatinny rails do have a tolerance, i
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/23/2011 at 18:57
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Excellent analysis, excellent representation...
So build me a <10MOA, 34mm mount...
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/23/2011 at 19:23
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How bout them apples.


Edited by 338LAPUASLAP - May/23/2011 at 19:25
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/23/2011 at 22:41
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LaRue Tactical SPR / M4 Scope Mount QD LT-104

Click on the picture to enlarge

The Industry Standard.
The LT104 is the best mount made for attaching high-power riflescopes onto flattop-style AR15's, period.
Ring Sizes Available:
Available with: 35mm, 34mm, 30mm or 1" rings

(We all have our favorites this one is mine) Devil

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/23/2011 at 23:17
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Wes, I've looked at LaRue.  The 0MOA is decent for my application, but I'm not mounting on an AR... it's going on my 338.  
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/23/2011 at 23:47
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LaRue Tactical .50 BMG QD   also available in 34mm

LaRue Tactical .50 BMG QD

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Designed to withstand the heaviest recoil
Our LT107 QD scope mount was designed by request for the U.S. Army M107 Military Long Range Sniper Rifle LRSR.50 Cal. We built-in 30 minutes of slope to get the most out of the scope's "come-ups". Folks ask "why three levers?", our answer is "because it's a .50 BMG and just looked like it needed three".

We've gotten Great reports coming back from the field...it appears the U.S. Army M107 Military Long Range Sniper Rifle LRSR.50 Cal can't shake this mount apart. When going into urban environments, the guys are swapping the long-range scopes off for CompM2's & CompM4's...this mount works well for continuous on/off type of stuff.



Edited by Urimaginaryfrnd - May/23/2011 at 23:54
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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/24/2011 at 00:53
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Jon A
 
Thanks a lot for your opinions and I appreiciate your comments. 
When I started the designwork on the mount system I actually started a thread on Snipershide to take in users opinions about what it good and what is not. Users opinions are very important and I have learnt a lot from listening to various opinions.
Here is the thread.
 
Material
Of course can 6061 be as strong when more material is used, (so can plastic materials to) but more material often causes higher weight. To me the 7075 T651 is the perfect solution as we can make an very strong mount for a comparable low weight.
I have a number of times looked at other materials to make solutions on other applications better (not scopemountssystems), and for less weight and looked at good plastics as PEEK and materials as Magnesium.
But the ratio betwen the weight and the strength for 7075 is for really many solutions very hard to beat.
 
Another VERY important good thing about the 7075 is the threads.
6061 are very soft and those threads often needs helicoils to withstand use.
When using 7075 there is no use for helicoils cause the material is so hard that the threads will hold. It have so far not happend that anyone have succeded to destroy the threads on our mounts, and I can tell you  I have tried.
Of course it can be done, but that does require an urge to destroy it....
 
We avoid 7075 T6 and are only using the 7075 T651 as the later is relived and very much more stable for machining.
 
Contact area
When it comes to the contact area regarding the repetability there is more factors than the one you meantioned, there more things causing problems than dirt. When it comes to theory you are absolutely right about the drawbacks for the limited contact area, but in reality there is more postive aspects of the limited contact area than poor one.
 
1. Few rails are straight, if any. With using limited contact points instead of full engagement against the rail the potential that the scopemount will return to the same place is much higher.
 
2. Rails are often very poorly dehorned, and is pretty sharp at the edges for the crosslots. So there is a potential that one of those sharp edges in the future can be a sharp upstanding little thing that interferes with your scopemount. If this happends where the lessend contact area is there is no problems, but the problems will ofcourse remains the same if the sharp piece are at the contact area.
 
3. There is absolutely a potential for dust to be in the wrong place when you changes betwen two scopes on a picatinnyrail, So I don't agree with you here.
The lessened contact area are certainly making the life easyer for the operator.
 
When it comes to the mounts we make for AI 11mm rail and TRG 17mm rail there is no limited contactsurface. Reason for this is that those rails are straight, and are made out of steel and are very much more protected than the picatinny rail.
 
Its also important to understand that those mountingssystems have been designed for a military use under hard circumstances that would give the operator the best strongest mount, with the fewest parts, and with loads of future possibilitys for mounting assesories.
The idea to machine a mount as one piece instead of multiple parts are not cheap, but there is no screws that can loosen up and change the POI. Same thing where screws are used, such as clamping on to the picatinny or the top rings, there is four respectively six screws, as we know that those guns are spending lots of time in vibrating vehicles where screws more than occasionally loosens upp.
They have orignally been desinged for dedicated sniperrifles such as .338 where there is NO need for detachable scopemounts at all as QD might cause more problems than they solve. (I don't mind QD, QD is wonderfull or the right firearms for its needs,and I use QD mounts a lot as well, but NOT on sniperrifles)
All those features that are availble are of course costly, as they require a lot of machiningtime, and its made in Sweden and not Asia.
So fully understandable its not necesarry a mount for all purposes.
But for those who needs a high quality scopemount system its vise to at least have a look at it, see the parts and the machining before saying to much about the price.
 
I would really appreiciate if people with opionons drops me a PM with their emailadress so I can email out a catalog and a special PDF I made to explain the mount system.
 
Håkan


Edited by www.technika.nu - May/24/2011 at 00:57
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: May/24/2011 at 01:48
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[QUOTE=Jon A]First I want to say I'm not one to talk down another's products.  By all reports the Spuhr mounts are very nice indeed and plenty strong.  However, in order to better inform the customer I want to clear up some misconceptions that are being developed.

First, in my years as a Mechanical Engineer, one thing I've noticed is how non-technical people seem to place more importance on material choices than they may deserve.  The material choice is of course very important to the overall strength of the end product, but it's only one of many important factors.  In parts where the design and geometry can vary wildly, it is often far from the most important factor.  It doesn't take a horrible design, just a few critical mistakes--mistakes most wouldn't notice--to turn a very strong block of titanium or steel in to a very weak part.

For just one simple example that everybody can visualize as it applies here, let's consider the foot area of a mount/ring that grabs the picatinny rail opposite the clamp--the exact area we have seen several brands of 7075-T6 aluminum rings fail.  Here you have a critical cross section in bending.  If two parts have identical geometry and one is made from 7075-T6 and the other is made from 6061-T6, the 7075 part is nearly twice as strong for an ultimate static load.

But since the cross sectional moment of inertia is proportional to the cube of the thickness, if one increases the thickness of the 6061 part by only 30% you cut the peak stress levels nearly in half.  So now the 6061 part is just as strong for an ultimate load as the 7075 part with a thickness increase so small many wouldn't notice without it being pointed out to them.

What else has changed?  The 6061 part is twice as stiff.  This is important for return to zero which we'll discuss more later.

What else has changed?  The 6061 part has 10 TIMES the fatigue life.  That's right, roughly 10 TIMES the fatigue life.  There's more to a part's design than the ultimate tensile strength of the material.  Just because one can run 7075-T6 at high stress levels without yielding it, doesn't mean one always should if fatigue life is a concern.  

Now imagine if the 6061 part was made 75% thicker?  Twice as thick?  It would be so much stronger in every way it's not even a remotely fair comparison.   And that particular thin cross section can be thickened a great amount with little impact to the overall size and weight of the part.  That's just one example.

Of course one could make the same change to the 7075 part and it would be stronger yet.  But if it was strong enough before, now you're wasting your customers' money by charging them for a more expensive material which is not needed for the application.  If designed for stiffness and fatigue life means you come up with a thickness where 6061 provides way more ultimate strength than needed, you gain nothing by changing to 7075 except for the advertising.

One doesn't need to be an Engineer to understand these concepts.  I think most of the well informed customers, upon hearing it claimed that one part is stronger than another based solely upon the material choice will recognize that as advertising--which may or may not have basis in fact for parts with different geometry (quite often a whole lot more than 30% thickness difference).  

It's different when the geometry is fixed.  For example with a Picatinny Rail one can't simply make the lugs thicker, etc, because then it will be out of spec.  For a part like that one can reasonably assume that a titanium rail will be stronger and stiffer than an aluminum rail and so on if comparing like designs (full width slots, etc).

Next, the issue of return to zero.  There seems to be a myth that got started a year or so ago that less contact area somehow results in better return to zero performance.  This myth relies upon a spec or two of dirt being in the contact area of one mount, messing it up, where another mount which doesn't have that particular contact area can't be messed up by that particular convenient particle of dirt.  It follows with that logic the best return to zero mounts/rings are those with no contact area at all--the ones held in position above the rail by the power of The Force.

Seriously, since the only place dirt tends to collect on picatinny rails is the bottom of the slots--and I don't know of any mount or ring that contacts there--it's quite far-fetched.  The top surface and the bottom of the sides of the rail, where most of the contact occurs, are quickly and easily wiped in the odd case of somebody having placed a pile of dirt there but usually remain quite bare.

What less contact area WILL mean, without fail, inescapably and without requiring a convenient piece of dirt for the assist, is higher bearing stress levels.  This means more deflection when the mount is torqued to the rail.  When less contact area means that contact is supported by shorter lengths of cross section (not to mention thinner) as in the foot example above, that means many more times as much deflection under the same clamp load from the clamp on the other side.

The magnitude of deflection is important because it determines the scope's final position above the rail.  A large amount of deflection can be felt when torquing the mount/rings to the rail--how quickly the fasteners go from finger tight to torqued.  Of course that also depends upon the rail material and the side clamp design.

A large deflection wouldn't be a problem if one can ensure the exact same amount of clamp load is applied to the clamp every time--the scope will always be in the same place.  If customers always used pro quality, often calibrated torque wrenches, and meticulously cleaned and lubricated the fasteners with ARP Ultra-Torque™ moly lube (if you build race engines, you'll know what that is), you could count on pretty close to the same amount of preload on the clamp every time.

Of course in the real world that won't happen.  Even if the customer is using an accurate torque wrench, the fasteners may be dirty, clean, wet or dry…the anodize underneath the heads won't look the same after 5 years of use as it did the first time so they'll make for a different amount of friction, etc.  In other words, the preload will vary even when the customer is trying.  

If the total amount of deflection under this preload is greatly reduced, then the variation of the magnitude of the deflection with variations in preload will also be greatly reduced--in other words the scope goes more closely back to the same place every time.  That's why stiffness is an asset for repeatedly returning to zero.  And in my case I wanted the customers to have satisfactory results using no torque wrench at all.  Of course it's always better to use one but a mounting system that will be "close enough" in a pinch without has an advantage.  

Much the same applies to increasing the bearing area of the recoil lugs, although this will be most noticeable on heavy recoiling rifles--particularly those with an aluminum rail.  With such rifles, one often notices upon re-installation of the scope the first shot is "out of the group" while successive shots land back at the original zero from before the scope was removed.  This is due to the mounting system flexing together, "taking a set" during the first shot.  It can also be exacerbated when a scope is moved from rifle to rifle, rail to rail.  Even quality picatinny rails do have
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An interesting discussion about scopemounts as well is the one steel vs Alu.
When comparing normal construction steel to 7075 they are very close in strength.
So 7075 changes the whole discussion about steel or alu.
 
Our rings are 4mm (.157") thick to give a very high strengt for the ring, but also to give sufficient strenght for the thread. That is something the 6061 never could do.
 
Same thing with our interfaces, they could never work in 6061.
And here is a differance betwe this and other solutions, this is a mounting system.
I have to consider the mounting of lasers, secondary sights, IR equipment, NV and other stuff on the mount, not just the scope it self, so therefor a change to 6061 would never be possible.
 
The repetability does certainly not suffer for beeing made in 7075 instead of the 6061 as the 7075 is much harder. The harder the material is, the less deflection and less prone to future problems due to wear and deflektion.
 
Jon, you'r remark about the torque wrenches are definitely interesting, and I personally don't really belive in using torque wrenches in the field due to the reasons you listed.
But a working solution instead of the torque wrench in field is to use it when installing the scope at home, mark the screws and then when reinstalling the scope rotate the screw back to the same position as before.
That would likely give the highest possible repetability, regardless of the make of the mount.
 
Håkan


Edited by www.technika.nu - May/24/2011 at 02:56
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Originally posted by www.technika.nu www.technika.nu wrote:

Another VERY important good thing about the 7075 is the threads.  6061 are very soft and those threads often needs helicoils to withstand use.  When using 7075 there is no use for helicoils cause the material is so hard that the threads will hold.

This makes assumptions about the design.  With the correct fastener and thread protrusion, it is a non-issue.  When large Grade 8 fasteners will twist off their heads (usually in the 80-100 lb-in range, which is nearly three times the specified torque) without damage occuring to the threads, making the threads stronger accomplishes nothing.
Quote Our rings are 4mm (.157") thick to give a very high strengt for the ring, but also to give sufficient strenght for the thread. That is something the 6061 never could do.

I won't speak to your design, but with mine the customer is free to torque all six ring screws 50 lb-in if he likes and the rings will be just fine.  His scope will be completely crushed (I use a steel bar when testing), but the rings/mount will be fine.  So again, there is no lack of strength which needs to be improved.
Quote 1. Few rails are straight, if any. With using limited contact points instead of full engagement against the rail the potential that the scopemount will return to the same place is much higher.

Limiting contact area does little for a rail which is not straight.  Making the contact areas close together will.  For example if you place two rings right next to each other on a warped rail, the misalignment will be small.  If you separate those rings several inches as you would when mounting a scope, misalignment will be large.  

The amount of contact area each ring itself has is meaningless.  For one piece mounts that translates to length of the mounting area.  How much contact area you have along that length means little.
Quote 2. Rails are often very poorly dehorned, and is pretty sharp at the edges for the crosslots. So there is a potential that one of those sharp edges in the future can be a sharp upstanding little thing that interferes with your scopemount. If this happends where the lessend contact area is there is no problems, but the problems will ofcourse remains the same if the sharp piece are at the contact area.

No quality rail will lack deburring along its top and side surfaces.  Even most cheap rails don't.  If a guy does find a rail that does, it should be pretty obvious he should hit it with a file before mounting something on it.  I'm certainly not going to design a mount around that low probability possiblility.
Quote 3. There is absolutely a potential for dust to be in the wrong place when you changes betwen two scopes on a picatinnyrail, So I don't agree with you here.

There's potential I will win the lottery as well.  Simply put, relying on some "chance" that specific dirt is going to affect one mount but not another is much too weak a case upon which to make claims that less contact area returns to zero better--claims constantly made without qualification.  Especially when there are so many other aspects of the design that affect return to zero performance that are guaranteed to happen every single time you bolt it on.
Quote its made in Sweden and not Asia.

That's nice.   Mine are made in the USA.   I want a cookie.
Quote The repetability does certainly not suffer for beeing made in 7075 instead of the 6061

I didn't say that.  I said small amounts of bearing area, short lengths of thin cross sections cause more deflection than long lengths of thick cross sections, etc, which is true regardless of which alloy is used.
Quote as the 7075 is much harder. The harder the material is, the less deflection and less prone to future problems due to wear and deflektion.

Harder?  As in surface hardness?  Is that before or after the Type III Hardcoat Anodoze?  You don't seem to have the most basic understandings of mechanics of materials.  We aren't pricking these things with a tiny indenter.  We're putting large loads on them.

The bearing area is just where the load gets into the part.  This gives way to compression, shear and tension/compression from bending stresses as the load travels through the part.  This is why I mentioned the cross sections which back up the bearing area.  A short, thin cross section will deflect more than the long, thick cross section.

That's regardless of alloy.  There is no meaningful difference in stiffness between 7075 and 6061.  Change one part to titanium or steel, where the modulus of elasticity doubles or triples, and now you've got a different ballgame.  But between aluminum parts, the higher ultimate tension strength means nothing to stiffeness unless one part is actually yeilding.
Quote Same thing with our interfaces, they could never work in 6061.

That may be the case, I haven't looked closely at all your interfaces.

Keep in mind I am not saying your choice of 7075 is a poor one.  It's a nice material.

What I am saying is the bold claims that your mounts are "the strongest" in general simply because they are made from 7075 are not backuped up with any Engineering fact.  They are simplistic and seem to be born of a lack of knowledge of how parts would be analyzed, much less results of any actual analysis.
Quote But a working solution instead of the torque wrench in field is to use it when installing the scope at home, mark the screws and then when reinstalling the scope rotate the screw back to the same position as before.

Uhm, yeah, that's not going to be very accurate.  So many variables, from the finish of the part under the head to the cleanliness of the thread can affect the torque enough to put that fastener head in a different orientation each time when properly torqued.

Edited by Jon A - May/24/2011 at 14:38
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Originally posted by koshkin koshkin wrote:

Jon, 

Can I use this on my website (properly attributed, of course)?
I am thinking of writing a piece on different scope mounts and I could use a nice discussion on materials.

ILya

Certainly.
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I really didnt realize until yesterday that you are the producer of Aadmount and that explains some of your opinions and your irritation.
 
And you are absolutely right, a mount in 6061 can certainly be made as strong when more material is used. And there is most certainly a good market for it, as a number of customers love heavy guns. And that is good, cause then we are not fighting about the same customers, as my customers so far have been looking for as light as possible in combination with ruggedness.
The weight differance is almost about those 30% as you earlyer calculated on.....almost 3 oz more.
But I don't wanna use more material, I wanna use less, and I wanna make the mount even lighter, but still with an exeptional strenght.
 
Hardness
The material hardness on 7075 is about 150 Brinell while on 6061 its about 95 Brinell.
Yes we both put on a hardcoat so the surface have the same hardness.
The repetability is not gained by soft material underneat of the surfacetreatment.
If the scopemount sometimes are misstreated such as lying in the bag or hit on one of the contact surfaces when not mounted on the gun there is a higher potential that the softer material on the contact surfaces will permanently deflect a little bit.
 
Rails
Don't know what world you are  living in, but I have seen plenty of picatinny rails with pretty poor deburring of the sharp edges. Yes US made rails too... When such a rail is handled in combat and exposed to the enviroment there is always a risk that small deflections at the corners can happend.
Your opinion is that it not likely going to happend, my opinion is that I wanna find a solution to limit its bad impact on repetability.
 
Contact areas
In the real world there is dust, sand and other problems.
I don't just hope there isent, I wanna minimize the users problems with those and an very easy way of getting arount parts of that problems is to limit the contact areas.
We will likely never agree on this, and we don't have to either.
 
Threads
We are talking about different kinds of threads.
First the threads used for holdning the top rings can absolutely with your construction be made sufficient strong in 6061, no question about it.
But that is also to limit the design to where you can have fairly long threads, but many other solutions can't be made with those longs threads and then the choise is either helicoils or harder material such as 7075.
For my interfaces where there is a very limited lenght on the threads there is not much choise than using 7075.
 
Material price
The differance in material price when buying billets is very little.
I expect the material price differance for one mount to be less than 5 dollar.
 
Jon, there is certainly a number of things we never will agree upon, and we don't have either.
Cause loads of customers will buy your mounts cause the like the height, weight, design and made in USA.  My product is not even a mount, it's a mounting system with a completely another pricetag but also with completely other possibilitys that will atract other customers.
 
So I wish you a very good luch with your production.
 
Håkan
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This discussion demonstrates a level of professionalism and an effort of respect between two product designers/ producers.

I have to say that it has been educational and clearly shows that if we all seek to respect one another's opinion (be them educated and logically explained), we can achieve greater harmony to further the production of scopes and accessories. And more importantly provide the user and educate the public on the varied applications that exist.

Kuddos to both Jon and Hakan!
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Originally posted by www.technika.nu www.technika.nu wrote:

...And you are absolutely right, a mount in 6061 can certainly be made as strong when more material is used...The weight differance is almost about those 30% as you earlyer calculated on.....almost 3 oz more.  But I don't wanna use more material, I wanna use less, and I wanna make the mount even lighter, but still with an exeptional strenght.

I don't think you understood a single thing I said.  The point was for certain parts, only a small amount of material needs to be added to a critical section adding negligible weight (if you know what that critical section is and how it works), and if you want to match the stiffness and fatigue life you need to add that material to the 7075 part as well.

The weight of my mount has nothing to do with this as the extra material in the critical sections is of negligible weight.  There is some extra weight on my mounts--in the bodies where it's not needed for strength.  With more machining time and cost much of that could be hollowed out.

But you were correct--these mounts were never intended to be lightweight.  There were already plenty of lightweight, light/medium duty mounts on the market and I intended these mainly for the big precision rifles with big, heavy scopes where nobody will notice a couple ounces.  I have a hollowed out version on the back burner if/when I determine enough people will pay extra to save a couple ounces to make production worthwhile.

With my rings, on the other hand, weight was a bit more important.  And they came out at similar or even less weight than competing rings--even though they have greater strength and stiffness by many measures.

Quote Hardness
The material hardness on 7075 is about 150 Brinell while on 6061 its about 95 Brinell.

Again with the surface hardness.  This is just displaying the fact you have no clue how to calculate or analyze for the stiffness of a part in bending.  Surface hardness never enters the equation.  And I strongly suspect had you known beforehand both materials will have the same surface hardness after coating you never would have brought it up.


Quote Rails
Don't know what world you are  living in, but I have seen plenty of picatinny rails with pretty poor deburring of the sharp edges. Yes US made rails too...

On what brands of rails and AR15 uppers have you noticed this poor workmanship?

Quote Contact areas
In the real world there is dust, sand and other problems.

In the real world, the notion that it is THE all encompassing determining factor in a mount's repeatability, is a fantasy.

Quote Threads
We are talking about different kinds of threads...but many other solutions can't be made with those longs threads and then the choise is either helicoils or harder material such as 7075.

Here you are correct in a way, although putting it like that is a somewhat backward design process.  Instead of picking a material and then being limited by its allowables throughout the design process, it's better to come up with a design and then select a material with the required properties to make it work.  Of course there is some iteration back and forth fine tuning things after both are roughed out.  

The point is if long threads with the screws being encapsulated by the body profile are there because I like them that way and customers like them that way, material choice was not a limitation for the design because that's not the reason they were made that way.
 
Quote Jon, there is certainly a number of things we never will agree upon, and we don't have either.

That certainly appears to be the case.  Unfortunately most of the disagreements appear to exist due to the fact only one of us has the education and background to truly know the answers to these questions. 

Once again, I have absolutely nothing against your mounts.  They appear to be very nice indeed.  And yes, 7075 is a nice material. 

What I have a problem with is your constant blanket claims which are not based in fact.  Especially those that put other products in a poor light.  Properly Engineering an assembly and having some idea how strong it really is when you're done is not as simple as picking a raw material out of a catalog.
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Jon,

When you talk about the rings you made, are you referring to a new model that has separate rings? or about the rings on the one piece mount?

Oh, by the way, if you are trying to gauge interest in a hollowed out light weight version of your mount, I am in.

ILya
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Originally posted by koshkin koshkin wrote:

When you talk about the rings you made, are you referring to a new model that has separate rings?

Damn ILya, you don't miss a thing!  I was waiting to start a separate thread to announce them until I had a bunch ready to ship, etc, but I guess I'll have to give you a sneak peak:





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Originally posted by Jon A Jon A wrote:

Originally posted by koshkin koshkin wrote:

When you talk about the rings you made, are you referring to a new model that has separate rings?

Damn ILya, you don't miss a thing!  I was waiting to start a separate thread to announce them until I had a bunch ready to ship, etc, but I guess I'll have to give you a sneak peak:




My apologies for paying attention Big Grin.

When are they going to be available?
Also, are the cross slots Picatinny spec? or Weaver spec?

ILya
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They're Picatinny.  I should be shipping in a few days.
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I saw the light weight rings on the Aadland web site the other day. Are you going to come out with a rail, Jon?
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I weighed the options and bought a Near mount with MRDS mount caps.  Recommended by some of my associates at Picatinny.
 
 


Edited by Kickboxer - May/27/2011 at 08:05
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