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SEMI-PRO SCOPE MOUNTING

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John Barsness View Drop Down
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    Posted: January/08/2010 at 11:02
This is the January 2010 column by John Barsness, one of the co-authors of RIFLE LOONY NEWS, a quarterly on-line magazine available through www.riflesandrecipes.com.
 
SEMI-PRO SCOPE MOUNTING

 

            Over the years I’ve seen scope mounting screwed up in just about every way imaginable, even by so-called professionals. One was the head technical guy at a custom rifle-making firm. Let’s call him Mr. Screwdriver.

            Mr. Screwdriver was very firm in his opinion that one brand of scope (let’s call it Acme) was a real piece of junk. This was because he’d had so many “fail right out of the box.” His favorite was a brand we’ll call Omega. He claimed Omega scopes almost always worked correctly.

            I hadn’t had nearly the same kind of bad luck with Acme scopes, so this puzzled me—until discovering, by accident, that Screwdriver was a firm believer in mounting scopes firmly, tightening the ring screws down until they literally crushed the scope tube. The tube-walls of some scopes are heavy enough to withstand such abuse, and the Omega company makes pretty heavy scopes. The Acme company made lighter scopes, and they were pretty sick puppies by the time old Screwdriver got done mounting them.

            On another occasion I purchased a new Merkel K-1 single-shot rifle from a big nationally-known gunsmithing firm and retail store. It was a package deal, with a 3-10x Swarovski mounted on the rifle. I wanted to put a different scope on the rifle and use the Swarovski somewhere else, so put the K-1 in my rifle vise, selected the right screwdriver head, and…nothing happened. The ring screws didn’t budge.

            Now this was an interesting situation. Evidently Torx-head screws hadn’t yet appeared in Germany, because the mount-screws had hex-heads. These can strip out with too much pressure, so I put a drop of Kroil on the side of each of the screw-heads and left the rifle overnight. The next morning the screws popped loose, but I could hear them crack as they came free. The Swarovski’s tube appeared to have a couple of slight “waists.”

            Mounting a scope is actually pretty straightforward—literally. The scope should be lined up with the bore of the rifle, and stress-free. Before starting we should first read the instructions for the mounts, because sometimes they contain how much torque the manufacturer recommends applying to the various screws. If there aren’t any recommendations, then it surely doesn’t hurt to contact the mount maker and ask. A lot of people assume all the screws should be really tight, but as we have seen, this doesn’t work on rings. Normally base screws should be pretty darn tight, and ring screws just tight enough.

            Talley, for instance, recommends 15-20 inch-pounds of torque on their ring screws. This isn’t much, since I can apply it to the Torx screws on Talley rings while holding a standard screwdriver with what might be termed “normal” pressure from the thumb and first two fingers of my right hand. I tested this with the Brownells Mag-Tip Torque Handle, a fairly expensive but accurate. Far less expensive models can be purchased, but the better the driver the more accurate its work.

            I have heard many people blame Talley rings for putting “ring marks” on their scopes, but unless something else is wrong I’ve almost never had Talley rings mark up a scope tube. I can only assume other people have a problem because they tighten the ring-screws too hard.

            The exception is when the tube of the scope doesn’t actually measure 1” or 30mm or whatever. This isn’t an unknown phenomenon. I’ve seen it in both “affordable” and quite expensive scopes. Slightly oversize and undersize tubes are likely to be marked by rings, the first due to the obvious reason that the rings are too tight before the screws are torqued. The second often happens after the scope shifts during recoil, when the owner cranks some more on the ring screws.

            One solution for slightly oversize scopes is lapping or reaming the rings. I have mixed feelings about this, even though I own and sometimes use the equipment to do either job. Generally ring-reaming should be like turning case necks on handloads: only as much metal as necessary should be removed. This means just enough steel or aluminum to allow the scope to be mounted without stressing the scope tube.

            Lapping takes longer but has the virtue of only removing a little metal at a time. Reaming is quicker but too many people go too far with it. I have a Dave Manson 1” ring reamer, but it should be used gently, and then the rings should be lapped a little to knock the edges off before mounting the scope.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote SVT_Tactical Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 11:22
Good info,  i've seen seveal guys at the club or range with improper mounted scopes that have the "waistband" and blame the scope or gun.  Everyone need a torque wrench like the wheeler!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 12:49
Once again, a great read.  Thank you, John.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote pyro6999 Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 12:53
so true jb, i think there is a lot of people out there who think the tighter the better.
my ffl was notorious for over tightening screws, im sure some of you may remember the troubles ive had over the years with rings. he tightened the rings down so hard that they stripped the threads on the rings not on the screws. i cant understand why some people who mount a lot of scopes dont have a torque wrench to get it right with. im lucky my boss has a very nice matco tools 1/4" drive inch lb torque wrench. i wont let anybody else mount my bases or rings ever again.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SVT_Tactical Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 12:59
Thinking back on a good horror story with scope mounting.  I went with my neighbor to get a gun scope combo and when we checked it the front was finger loose and the rear ring was stripped they had tightened it so much.  Then when putting a new base on we realised the reciever was stripped and they had used JB weld to keep the screw in the reciever!.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cheaptrick Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 13:00
Originally posted by pyro6999 pyro6999 wrote:

so true jb, i think there is a lot of people out there who think the tighter the better.
 
If it ain't tight, it right!! Wink
 
Good read as always, JB.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SD Dog Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 13:07
Thank-you for the article.  Sound advise again.

PS.  Loved your Kudu article in AH.  Someday.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 13:31
Good article John as always.

I see a problem with shimming two piece bases to make your scope reach its center.  If you shim one of them then it easily could be on a slightly different plane than the other base.  Say you shimmed the back base.  So when you put your rings on and mount your scope your scope will only initially contact the back edge of the front ring and the front edge of the rear ring.  Then you tighten it down and somewhat force it into the rings so it makes full contact all through the ring.  This will cause your scope tube to be in a slight bind.  Sure your scope might be mechanically centered, but your rings could now be out of alignment.

I see the same problem with Redfield type windage bases.  You push the back one over to the right and now the back ring is in a different plane than the front ring.

I use Kokopelli accurizing kits to mount all my bases and rings and I have seen first hand how far off shimming one of the bases can make it.  Even when using one piece bases if the reciever is not square (which they seldom are) then when you tighten down the base your rings become uneven.  But with a 1 piece base you can bed the base and know for a fact that it is perfectly straight.  If all done correctly lapping becomes not really needed.

I bet a lot of scope are ruined because they are put in uneven rings which puts a slight bend in the tube and causes a failure.  I often wonder if that is why so many scopes don't work for people and then they send them back and the manufactures say they work fine.  When the customer gets it back and mounts it back up he immediately has the same problem because the mounts are not square.

Below is a pic out of a review a USGunner from snipersparadise did using the Kokopelli kit.  This is a one piece TPS base before him bedded it and you can see how far out of alignment it was.  I can imagine that shimming a 1 piece base could make it even worse.

Seeing pics like this and seeing this exact same thing on my personal rifles, I can definitely see the benefit of using rings with rubber inserts to solve the problem simply.  Or taking bigger measures like bedding bases.  I am not sure that just shimming will solve the problem without causing others.




Edited by supertool73 - January/08/2010 at 13:34
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Post Options Post Options   Thanks (0) Thanks(0)   Quote koshkin Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 13:43
Very nice article, John.

One point I will add though, is that if you are worried about thermal expansion, shims are just a bad idea, especially when using steel bases.

Most common aluminum alloys have similar thermal expansion coefficients, so aluminum shim under an aluminum base might work.

However, different (and commonly available) steel types have thermal expansion coefficients that are all over the place, sometimes differing by more than hundred percent.  Since we usually have no idea which exact type of steel has been used for the base and/or for the shim, it is bets to not mess with it on rifles where you worry about thermal effects.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jonoMT Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 15:20
I suppose the only surefire solution is to build a rifle off a Surgeon or other similar custom action with a Picatinny rail machined right into the action. Absent the lottery winnings for that, it does make it somewhat easier to rationalize my recent purchase of a Premier scope and Seekins Precision one-piece base and rings. The precise engineering and machining on all three of those components removed much of the tedium of mounting. I was still very careful and took my time, keeping everything absolutely clean. Yet all I did was blue loctite-bed the base to the action, place the ring bases, and check eye relief. Then I leveled the base of the scope to the rail with feeler gauges and tightened the ring caps, being careful to both follow the manufacturer's torque specs and to get the rings utterly even (I used the feeler gauges to check this as well).

So buying quality gear can help you avoid some of these mounting steps and a lot of the aggravation, as well as having to own specialty tools. I only own a few rifles so buying collimators and accurizing kits just doesn't make sense in my situation. I sprang for a nice torque wrench because that gets used on the action screws as well. The additional benefits of quality gear is that the same careful attention to detail as it applies to mounting has (almost always) been applied to other aspects of a scope's functionality and reliability.

supertool73, that is surprising that a one-piece base like that would be deformed like that. I will admit that is one drawback to the method of mounting I am using. I am assuming my actions are true and if they aren't I hope my lightly bedding the base with loctite makes up for it...'cause I ain't checking. So far, field results have not indicated a problem with the rifle or scope...just shooter error.
Reaction time is a factor...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 15:31
Just because you are using seekins doesn't mean it will be imune from the problem.  I have a seekins base and rings and I still had to bed my base.  The rings and base might be matched perfectly as I am sure they were because Glen is a great machineist.  I have had TPS, IOR, and had to bed both of them as well.  If the receiver is not square once you tighten down the front and back of that base then it now bows right along with the action.  Making your rings point in slightly different directions.  

The guy that wrote that review took his TPS base and rings into a specialty shop that has machines that can tell how precise things are and he said they were amazed at how perfect his base and rings were machined.  But once he tightened it down and it bent it meant nothing.

I am of the exact opposite opinion of you.  The fact that you spent $2000+ on a scope is the exact reason to buy the tools and equipment to do it properly. 

Locktite it not really going to bed your base if it is really off.  You need to use somekind of bedding compound just like to bed the action to the stock if it is really off. 

But on the other hand lots of people get away with never doing anything.  But lots of people have problems as well that I bet could easily be traced to improper mounting.  It worries me that if one of my expensive scopes break and it is because of my mounting issues that they may not fix or replace it.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SVT_Tactical Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 15:48

I have a 10/22 that i had a guy test tig weld the base onto the receiver checking it for square and being extra careful to see if he coud do it to some other action that he was going to do.  It did work and every scope I have mounted on it has been within 1" of center at 50yds with the scope at mechanical center.  Did fugly it up though.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote lucytuma Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 16:09
Nice read John, as a carpenter by trade, I enjoy working with other carpenters to learn new or easier tricks of the trade.  So I was pleased to read how you go about scope mounting and compare it to the way I do it.  Are practices on mounting scopes are very similar, but it's always good to be refreshed, if not reassured.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jonoMT Quote  Post ReplyReply Direct Link To This Post Posted: January/08/2010 at 22:45
Originally posted by supertool73 supertool73 wrote:


I am of the exact opposite opinion of you.  The fact that you spent $2000+ on a scope is the exact reason to buy the tools and equipment to do it properly. 


I think the only tool I'm missing in this equation is the Kokopelli alignment bars. As I mentioned, I have torque wrenches (good ones too...Seekonks). And I have faith that Seekins and Premier did their jobs in making the components. So I don't think we are so much opposite in opinion as much as I'm just saying that - aside from the weak link in my scope mounting chain, which is Remington's work on the action - there's no need for all the rest of that work if one simply buys quality gear in the first place.

But I am going to invest in a set of the 34mm scope bars. I don't mind repeating the mounting process to see that it's done right. If there's misalignment, then I'll work on the base.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slodancr Quote  Post ReplyReply Direct Link To This Post Posted: January/09/2010 at 10:41
Very interesting article, thank you. I am preparing to mount a scope on a new squirrel gun. The rifle is a savage Mark II with a rounded action top. My local FFL shop could only get me weaver 2-piece mounts for this rifle. When I mounted the bases, there appears to be a lot of space between the action and the edge of the bases. I am not convinced this is the best type of base for this particular application.
 
Considering the info presented in this article, the idea of milling a longitudinal groove would be ineffective, if not downright damaging to the base.
 
Any suggestions or comments on a better base for a rounded action would be greatly appreciated. Also, if this is the best I can do for this rifle, what suggestions does anyone have as to "truing" these bases to the top of the action?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kokopelli Quote  Post ReplyReply Direct Link To This Post Posted: January/12/2010 at 19:40
Apretty good synopsis, John.  I will , however take exception to your recommendation to use the piinted alignment rods to test axial alignment through the scope rings.  They are mathematically incapable of telling you anything about axial alignment.  They can readily give a "false positive".  To prove this is truly a geometry problem and the pointed rods lack one element to solve the problem of axial alignment. Prove it to yourself by simply taking two pencils, or ball-point pens and lay them on a table with the points touching and then swing the ends around like clock hands and see if you can tell when the pencils are lined up exactly with each other.  This should be easy because the table top aready gives you alignment in one plane.  There are no planes at all in scope rings, just an infinite amount of misalignments with only one true axial alignment.  Read the post by supertool173.  Rings and bases are now being made very accurately, but the receivers are not.  Most misalignment problems stem from there.  Bedding the base is the only practical method available to the average shooter to straighten that out, but you must use a tool that will show you true axial alignment, not a "false positive".
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Post Options Post Options   Thanks (0) Thanks(0)   Quote NV Hunter Quote  Post ReplyReply Direct Link To This Post Posted: January/13/2010 at 13:20
Great article, thannk you John.  What are your thoughts on installing larger screws (8x40's) and epoxying the bases to the receiver of mag caliber rifles with muzzlebrakes?  NV Hunter
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jonoMT Quote  Post ReplyReply Direct Link To This Post Posted: January/13/2010 at 19:01
Originally posted by kokopelli kokopelli wrote:

To prove this is truly a geometry problem and the pointed rods lack one element to solve the problem of axial alignment. Prove it to yourself by simply taking two pencils, or ball-point pens and lay them on a table with the points touching and then swing the ends around like clock hands and see if you can tell when the pencils are lined up exactly with each other.  This should be easy because the table top aready gives you alignment in one plane.  There are no planes at all in scope rings, just an infinite amount of misalignments with only one true axial alignment. 


This will be a good excuse to render out a 3D PDF from my new CAD program. I'll make a couple bars and tilt one slightly in one axis only. You can rotate the objects around in Acrobat and see this test in action.
Reaction time is a factor...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kokopelli Quote  Post ReplyReply Direct Link To This Post Posted: January/13/2010 at 19:21
Originally posted by jonoMT jonoMT wrote:

Originally posted by kokopelli kokopelli wrote:

To prove this is truly a geometry problem and the pointed rods lack one element to solve the problem of axial alignment. Prove it to yourself by simply taking two pencils, or ball-point pens and lay them on a table with the points touching and then swing the ends around like clock hands and see if you can tell when the pencils are lined up exactly with each other.  This should be easy because the table top aready gives you alignment in one plane.  There are no planes at all in scope rings, just an infinite amount of misalignments with only one true axial alignment. 


This will be a good excuse to render out a 3D PDF from my new CAD program. I'll make a couple bars and tilt one slightly in one axis only. You can rotate the objects around in Acrobat and see this test in action.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kokopelli Quote  Post ReplyReply Direct Link To This Post Posted: January/13/2010 at 19:29
You can save yourself some trouble and look at the picture supertool173 submitted.  The missing element is there, the machined ends.  With one bar in each ring you now have a three-dimensional solid projection of the "hole" through each ring.  Bring together and compare the ends.  Do the peripheral edges match?  Are the ends flat together?  If the answer is yes to both questions you have axial alignment because you have  recontructed a solid bar through both rings!  Voila, Axial alignment!  What could be simpler?  If they don't match, you have a little work to do, but you have a tool which will tell you where and how much.
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