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Real Poor Shooter w/factory ammo, how much can I really expect?

 
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  #8  
Old 08-28-2010, 06:12 PM
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Re: Real Poor Shooter w/factory ammo, how much can I really expect?

Didn't you say the barrel has a 1 in 10 twist? That may not be enough RPM for 160/168g. VLDs. The standard seems to be 1 in 9 twist. On most of my customs, in 7mm cal., I like a 1 in 8 twist for long/heavy bullets. Also, many used rifles have copper fouling/build up problems. Give the bore a good cleaning with Sweets 7.62 bore solvent. Follow the directions, it's strong stuff!
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Last edited by shortgrass; 08-28-2010 at 06:19 PM. Reason: more info
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Old 08-28-2010, 06:27 PM
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Re: Real Poor Shooter w/factory ammo, how much can I really expect?

Quote:
Originally Posted by shortgrass View Post
Didn't you say the barrel has a 1 in 10 twist? That may not be enough RPM for 160/168g. VLDs. The standard seems to be 1 in 9 twist. On most of my customs, in 7mm cal., I like a 1 in 8 twist for long/heavy bullets. Also, many used rifles have copper fouling/build up problems. Give the bore a good cleaning with Sweets 7.62 bore solvent. Follow the directions, it's strong stuff!
This has crossed my mind, but even the Berger box reads "for rifles with 1 in 10 or faster". Most everything I read seems to point to not much advantage or disadvantage between 1 in 9 or 1 in 10 for the 160 gr. range of bullets.
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Old 08-29-2010, 07:41 AM
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Re: Real Poor Shooter w/factory ammo, how much can I really expect?

If you check the web sites of some of the custom barrel makers, those that recommend twist rates for bullet weights recommend a 1 in 8 for bullets above 140g. (I'm thinking Shilens' web site). Seems there's a discrepancy, sometimes, between what bullet makers and barrel makers recommend. I'd try some bullets weighing 140g. and less and see what happens. I'd make sure I didn't have that copper fouling, too. I see many barrels the owner says are 'shot out' and when I run a strong copper solvent thru them until the patches come out clean they go back to shooting. Ammonia based copper solvents will turn copper the color blue, so it's easy to tell when all or most of the copper has been removed. You may need to find a 'smith that has a bore scope for a good look-see. I have, also, seen dramatic changes by changing propellants or primers. Just because some say this is the best for that cartridge or load doesn't make it so. Every barrel is an individual and should be treated as such. Sounds to me, though, either the barrel is badly fouled or worn out, or you are shooting the wrong weight bullet. Any of those will make for a rifle that shoots 'patterns' instead of 'groups'. From this distance, all I can do is speculate.
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  #11  
Old 08-30-2010, 12:42 AM
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Re: Real Poor Shooter w/factory ammo, how much can I really expect?

I hear ya. I'm determined to get it to shoot 160s or have it re-barrelled. A couple of smiths are recommending 1:10 twists for 160, so hopefully it'll get them spinning fast enough. Going out to shoot tomorrow if nothing comes up. I loaded up 2 ladder tests and we'll see what happens.

Going to try a couple of loads with the Berger VLD. Reference material is scarce on that one so I'm going off what Walt Berger sent me for the .280 REM, and going above the max a bit.
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Old 08-30-2010, 09:10 AM
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Re: Real Poor Shooter w/factory ammo, how much can I really expect?

Quote:
Originally Posted by Troutslayer2 View Post
I hear ya. I'm determined to get it to shoot 160s or have it re-barrelled. A couple of smiths are recommending 1:10 twists for 160, so hopefully it'll get them spinning fast enough. Going out to shoot tomorrow if nothing comes up. I loaded up 2 ladder tests and we'll see what happens.

Going to try a couple of loads with the Berger VLD. Reference material is scarce on that one so I'm going off what Walt Berger sent me for the .280 REM, and going above the max a bit.
Here's a good article about calculating for proper twist rate.

Calculating Bullet RPM — Spin Rates and Stability AccurateShooter.com Bulletin

And, a calculator. Works good if you've got a good idea what your velocity is going to be (ball park) and have some info on the bullets you plan to shootl

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

Last edited by fj40mojo; 08-30-2010 at 09:14 AM.
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