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1/25/2018 7:38:29 AM
Posted: 8/10/2001 3:51:59 AM EST
I have been hearing so much about barrel twist rates. One opinion is if you use a bullet heavier than 55gr. the twist rate should be 1 in 10" or faster others say that 1 in 9" twist rate handles the whole spectrum of .224 bullet weights. The reason why I ask is that I recently bought a Colt Hbar with a 1 in 7" twist rate and want to avoid buying bullets that maybe a waste of money if the accuracy is not that good. If you have a 1 in 7" twist rate what is your personal experience as far as bullet weights.[?]
Link Posted: 8/10/2001 4:02:09 AM EST
Link Posted: 8/10/2001 7:24:23 AM EST
You can shoot any bullet above 55grs in weight. You can shoot 55's and below, but [i]certain[/i] expanding varmint bullets may tear apart during flight from the rotation unless velocities are kept under 2800fps or so. So far I've torn apart Sierra 55gr BTSP's and BTHP's this way.
Link Posted: 8/10/2001 12:30:12 PM EST
The 1/7 was generally develpoed for the SS109 heavier bullet, but M193 works fine. I am told that at distant ranges (+500m), pentetration is effected by using the different ctg, but thats penetration of steel helmets, and armoured vests, you'll have 'no worries' dealing with varmints etc.
Link Posted: 8/10/2001 12:44:50 PM EST
I was told that the only reason 1 in 7 was ever implemented was that tracer ammo could only be stabilized with such a twist. Otherwise, 1 in 9 will do fine with M193 or M855(SS 109).
Link Posted: 8/10/2001 12:54:26 PM EST
I have had 55gr Speer softpoint bullets fly apart when fired from 1:7 barrels. It rarely happens with 16" tubes, but frequently with 20" barrels. You probably will be fine if you don't use light weight varmint style bullets.
Link Posted: 8/10/2001 12:57:19 PM EST
All the military A2s I have seen have been 1/7, and our F88 Austeyr is 1/7 too, but the 1/9 has excellent results in both types of ammo. I am sure Colt has configured A2s in 1/12,1/9, and 1/7 for various clients throughout the world.
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