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Accurizing a rifle-discussion

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/07/2008 at 04:48
8shots View Drop Down
Optics Jedi Knight
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'lord of the flies'

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I have played around quite a bit with my 308 Rem700 Varmint. To date I remain dissapointed in the performance. The lack of obtaining a decent grouping can be attributed to many factors: bullets, powders, primers, loading, rifle , barrel bedding and so on.

I bought the Rem hoping that I now have the rifle sorted. I also bought a 308 Win cal in that this seems to be the most accurate target rifle.
 
I post below my most recent target. The one load of 42 gr and OCL of 2.819 inches gave an excellent grouping. Unfortunately I have not had a chance to re-test this load.
However, by changing the load by 1/10th of a grain at a time the effect seems to be quite drastic on the grouping. Bullet is 155 gr Palma at approx 2600ft per second.
 
The question is this: Is this normal? Is 1/10th of a grain a lot. I would not have thought that a rifle such as this would be this sensitive.
Has anyone had the same experience.
Is the level of sensitivity an indication something else is wrong?
Would squaring up the boltface (blueprinting) be of any value?
 
All comments appreciated!!!!
 
 
 
 
 


Edited by 8shots - October/07/2008 at 04:52
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/07/2008 at 08:50
Dale Clifford View Drop Down
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41.4 thru 42 look good and normal for this type of gun set up. sensitivity to small changes depends a lot on closeness to lands. the far left shot in each group is what I would expect from a left hand shooter, it occurs in right hand shooters on the right side of course. some long range shooters will use a 1/2 to 1 moa off set to accomoadate for this natural pull.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/07/2008 at 09:23
Mike McDonald View Drop Down
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It's not uncommon, that's for sure.
I'd observe that 155 palmas @ 2600 are slow for the bullet design but don't know how that would play into accuracy at close distance.
As you get near max for the rifle, you most likely are going to find there's a couple places in the load density that let you vary 0.3-0.4 grains with no adverse effect.
 
One of the biggest problems with remingtons is that the chamber may not be concentric to the bore.  Might look at cutting the barrel back enough to recut the camber with the barrel properly indexed.
Also take a good hard look at the crown.  Had one that would not shoot a group at 100 yards no matter the load or shooter.  Then found it grouped the same at 500 as it did 100.  Re-crowned the barrel and it became a very accurate rifle.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/07/2008 at 10:23
8shots View Drop Down
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'lord of the flies'

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Mike, it is an interesting comment you make about the chamber alignment. I had a knowledgeable guy look at the barrel with a borescope. He found copper fouling on one side of the barrel just off the lands, which led him to believe that the chamber is not cut straight.
I have tried higher velocities with rather worse results.
The crown seems ok, even as inspected by someone else.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/07/2008 at 12:09
Mike McDonald View Drop Down
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That would make sense.
With a non-concentric chamber each bullet is re-swawged as it enters the barrel which leads to some serious precession issues.  Faster would be worser.
If you can, set the barrel back about 1/2 the cartridge length and re-cut the chamber.  Doing this will also solve that really long throat length issue too.
 
At our range we see hundreds of factory remington VS, PSS and Ultra mags each year, with an overly large percentage having out of round or off center chambers.  the majority of rifles are 308 winchester.
Hoever, the ones that shoot really shoot well.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/09/2008 at 07:15
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Your load of 42 grains is good. I don't see a problem. Most rifles on this Planet don't shoot like that. Tubb's Final Finish polishing bullets can be used to polish the throat a bit and to make the jump of those bullets smoother, considering the (presumed) off-center chamber.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/09/2008 at 07:17
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Yes, it is not unheard off to have 1/10 of a grain make a difference. I used to load for a rifle that would shoot well with 46 grains and a specific OAL, but nothing else.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/09/2008 at 11:18
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Originally posted by 8shots 8shots wrote:

I have played around quite a bit with my 308 Rem700 Varmint. To date I remain dissapointed in the performance. The lack of obtaining a decent grouping can be attributed to many factors: bullets, powders, primers, loading, rifle , barrel bedding and so on.

I bought the Rem hoping that I now have the rifle sorted. I also bought a 308 Win cal in that this seems to be the most accurate target rifle.
 
I post below my most recent target. The one load of 42 gr and OCL of 2.819 inches gave an excellent grouping. Unfortunately I have not had a chance to re-test this load.
However, by changing the load by 1/10th of a grain at a time the effect seems to be quite drastic on the grouping. Bullet is 155 gr Palma at approx 2600ft per second.
 
The question is this: Is this normal? Is 1/10th of a grain a lot. I would not have thought that a rifle such as this would be this sensitive.
Has anyone had the same experience.
Is the level of sensitivity an indication something else is wrong?
Would squaring up the boltface (blueprinting) be of any value?
 
All comments appreciated!!!!
 
 
 
 
 
.....................Before you go and start re-aligning and re-barreling and all that jazz, try this for the heck of it and try solving the problem in the least expensive way.
 
Get yourself a rubber barrel de-resonator for about $20. Reducing your barrel`s vibrations or "harmonic resonance" will help to reduce your group sizes.
 
If your barrel is non-free floating position the de-resonator about 3/4" from the stock`s forend. If free-floated, start at about 1" from the muzzle.
 
They have a hole size for the heavier barrels..........Go to,,,,,,,,,"limbsaver.com",,,,,,"products" section. There is also a short audio/video to see plus installation instructions. If the de-resonator works like I think it will, then that will white-wash any alignment issues.  If you have a barrel alignment issue, the de-resonator won`t work as it won`t compensate for that.
 
Yes! 1/10 grain can make that much of a difference. 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/13/2008 at 09:31
8shots View Drop Down
Optics Jedi Knight
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'lord of the flies'

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I think that the barrel has the potential to be a shooter. This weekend I again tried stuff. I used new Lapua shells and then used the same ones with only neck resizing. Still no go.
I however placed in the mix some PMP cases. Now PMP (Pretoria Metal Press) is South Africa's only cartidge and case manufacturer. Quality is OK for hunting, but not top grade. The cases are notorious for differing capacity and the nexks have large runout.
So I took 5 random cases that I had used beore. The cases are outside neck turned to about 13th.
I will be danged if they outshot the Lapua!! However, before getting excited, I have tried these cases on numerous other occasions and the performance remains erratic.
The rifle is going in for surgery: Boltface squared up. lugs lapped and a new chamber cut.
 
 
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/13/2008 at 22:01
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The rifle is going in for surgery: Boltface squared up. lugs lapped and a new chamber cut.
 
 
If your going to have the chamber cut, you may consider sending an unprimed empty round set to the OCL that you prefer. That way you will eliminate some of the guess work you've experienced with it already. They can cut it to spec and you avoid unnessary throat length.
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/14/2008 at 06:00
8shots View Drop Down
Optics Jedi Knight
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'lord of the flies'

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Originally posted by Sgt. D Sgt. D wrote:

The rifle is going in for surgery: Boltface squared up. lugs lapped and a new chamber cut.
 
 
If your going to have the chamber cut, you may consider sending an unprimed empty round set to the OCL that you prefer. That way you will eliminate some of the guess work you've experienced with it already. They can cut it to spec and you avoid unnessary throat length.
 
 
Thanks for the tip. Will certainly do that.
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