Doin' the Twist

O

OldPPC

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I typically load bullets in the mid 50 low 60 grain range for my .223 varmint rifle. But I have a box of 75 grain A-Max bullets and I'm wondering what kind of performance I can expect from them with my 1:12 twist barrel. Everything I read pushes them through 1:8 or 1:9 twist, but I need something that will remain stable out beyond 600 yards and, with the 1:12 twist, can I expect those 75 grain pills to hold their own? Any experience you'd care to share appreciated.
 
Those 75gr bullets won't be stable from a 1-12" twist at any range. Sorry. I have found that 55gr bullets stabilize very well in a 1-12 twist, but much over that works better with 1-9".
 
Don't waste your time, just won't work.. I'm sure they need an 8 twist..

I have several bolt .223's with differing twist rates....
 
Thanks to all. That was a real education; appreciate your input. I'll hold off with the heavier pills until I get my 1:8 twist.
 
To Add to the Confusion

Some of the physics lessons that apply to getting the best accuracy can sure make it difficult for the newbie (I'm still a newbie) to grasp all this stuff. Here's some of the reason I posted the original question in this thread:

Comparing 6BR and .223

The 6mmBR web site (http://www.6mmbr.com/index.html) posts this statement in the 6BR Section:

"What Barrel Twist Do I Need?
The most versatile barrel is a 1:8 twist, from 26" - 28". This will shoot everything from 65gr FB bullets to 107 VLDs with great accuracy. For shooting out to 600 yards, in calm conditions, you may get best accuracy with custom 80-90gr FB bullets. These work best in a 1:12 twist tube. So far, the 1:10 twist has been a "tweener" that hasn't been as popular as a 1:8 or 1:12. On paper, the 1:10 should do well with the new low-drag FB bullets, and most 90gr boat-tails. The 95gr Berger VLD requires at least a true 1:9. But right now, when most people buy their first 6mm BR barrel, they chose a 1:8." (bold emphasis is my own)

The 6BR converts to .236 against .224 for the Remington. Difference = .012

The ballistics charts on the site for the 6BR and the .223 Remington include these specs., along with others:

............... Bullet .......... FPS..............Powder Charge

6BR

80gr ...... Berger.........3150.........30 W N135 (Outstanding accuracy in 1:12)

88 gr...... Berger.........3100.........31 Varget

90 gr...... Scenar.........3050.........W N540


.223


75 gr...... JLK VLD....... 2905.........24.5 H4895

80 gr...... Sierra..............2550.........W N140

80 gr....... Sierra..............2800.........24.4 Varget


Would that lead one to conclude that the only reason the heavier bullet might fail to stabilize over long ranges when launched from the .223 is because of the lower muzzle velocity?
To maintain some semblance of balance for purposes of comparison, when comparing the 80 grain loads, it’s astonishing that 350 FPS and .012 difference in bullet diameter could really have that much effect on accuracy?
 
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"Would that lead one to conclude that the only reason the heavier bullet might fail to stabilize over long ranges when launched from the .223 is because of the lower muzzle velocity?"

No, the difference is length of the bullet.
 
No, isn't 6BR..........

.243 VS .224 = difference .019??? :confused: Unless, you go .236 VS .219 = .017?? Am I missing, er, um, not firing on all eight??? :eek::confused::)
 
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