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  #1  
Old 10-19-2014, 10:03 PM
ab_bentley ab_bentley is offline
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Default Help! 20TAC

Shooting the 20TAC in the project rifle section. Shilen CM Match 1-12" @ 22". Shot it yesterday and today and the best group I could get from it was around 5/8" @ 135yds. Today I put 50rds through it with 10 different loads and the same thing yesterday. I have used an array of powders; AA2200, TAC, XBR8208, all at min to max loads. I also have used the 34gr Dogtown bullets and the 32gr VMax bullet. Seating depth from .020" into the lands all the way to ogive to case neck, nothing seems to works. I altered the tension of the action screws, the mag box isn't pinching. I changed stocks and that seemed to help a little, not anything earth shattering changed. I was curious what your opinions were.


The scope is a Nikon 3-9x40 the trigger is a Shilen standard @ 2lbs., the barrel is free floated from action to crown. The action sits in a Devcon bed with pillars that aren't touching the screws. The scope and bases are tight.


With every load I tried save a TAC load the groups were perfect triangles, which leads me to believe it's a harmonic issue/ fit issue. Although I know it's not as the bedding is stress free. All of the "bad groups" were at 1" again in a perfect triangle.




For once I am completely stumped.


Adam
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  #2  
Old 10-19-2014, 10:51 PM
trotterlg trotterlg is offline
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Wouldn't call either of those bullets real quality. Try a Berger 35 or a Nosler 32 which my 20BR with a 12 twist likes better than anything I tried. I used up the Bergers but I could send you a few Noslers. Larry
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Last edited by trotterlg; 10-19-2014 at 10:54 PM.
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  #3  
Old 10-19-2014, 10:54 PM
xring xring is offline
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Adam , I hate to suggest anything because I'm sure with your background that you have looked at the Crown , Trigger , Rings , etc. . You might try switching Scopes and trying V133 and H322 or AA 2015 .
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Old 10-19-2014, 11:02 PM
ab_bentley ab_bentley is offline
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I have a few more powders to try, but damn it's hard to think a barrel is this picky. Larry, I hear you on the quality bullets, but after shooting a few thousand through the 20VT and making them go into small groups it's hard to think otherwise. I have Bergers in the store but man alive. I will also be trying the 40gr bullets. I will try the better bullets tomorrow.


X, don't feel bad about advise. I may have over looked something.....


Adam
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  #5  
Old 10-19-2014, 11:06 PM
trotterlg trotterlg is offline
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I think the little Dog Town bullets are going a little faster now. Larry
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Old 10-19-2014, 11:08 PM
ab_bentley ab_bentley is offline
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On the contrary, these are moving around 3700fps with XBR, the 20VT was cooking @ 4100fps with them. I think I might switch primers too. The customer supplied me with WSR primers but I always use a SRM from CCI or Tula/ Wolf.


Adam
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Old 10-19-2014, 11:12 PM
trotterlg trotterlg is offline
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Put a lump of clay around the muzzle and see what difference it makes. Larry
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  #8  
Old 10-19-2014, 11:24 PM
ab_bentley ab_bentley is offline
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Like a dampener?


Adam
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  #9  
Old 10-19-2014, 11:37 PM
trotterlg trotterlg is offline
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Yep, it will tell you something about harmonics, it will either stay the same, get worse or get better, I would say if it gets better or worse you will find it is harmonics. Larry
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  #10  
Old 10-20-2014, 12:34 AM
xring xring is offline
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Adam , Powder choice made a big difference in my Tac20 .....unfortunately I can't find my actual Data . I had read many accounts of how good H322 was in the Tac20 . However , I was quite surprised that mine greatly prefers V133 over H322 .
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