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Posted: 3/14/2010 4:50:59 PM EDT
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If I want to make a dedicated upper to practice HP Match close range, who makes a 26" heavy barrel 22 lr barrel that's chambered for the .223 CMMG conversion?
Thanks |
| You can have a 26" barrel if you want to shoot 22lr at reduced velocity. You might have better luck with a closed action firearm, but a 26" barrel on an AR15 semi auto version won't do shit. I have tried it starting with a 26" barrel shortening it 1 " at a time. It gets faster till about 18". |
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What does velocity have to do with accuracy, OldCat?
For starters, velocity is NOT reduced in a semiauto .22. Second, why do you want to use an unmodified conversion bolt? Stick a collar on your bolt and use standard dedicated barrel. That way your little lead .22 bullets won't have to traverse 1 1/2" freebore before entering the rifling. This boosts accuracy. I'll bet Frank White at Compass Lake Engineering could fix you up, but not for the CMMG and not for cheap. A custom length will cost at least $350, plus$240 for a bolt (M-261 only). A benefit of the M-261 is that it can lock open on a USGI mag for single loading. If you're married to your CMMG bolt, check with Adam at Ballistic Advantage. |
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Quoted:
What does velocity have to do with accuracy? For starters, velocity is NOT reduced in a semiauto .22. Generally speaking a faster bullet will be more accurate because it spends less time in flight and is acted upon by gravity and wind to a lesser degree. Velocity and accuracy may or may not be a factor with a particular 22lr round and barrel. Every 22lr round and barrel will probably yield different results and some variations between individual rounds of the same brand. Common sense will tell you that an excessively long barrel can yield reduced velocities in a blowback 22lr semiauto design. I have tested it extensively on the bench using a chrony and recording data. To achieve maximum velocity you want the bullet to exit the barrel just as the pressure of the expanding gases peaks. If the barrel is too long for the powder charge the bullet actually starts to slow in the barrel as friction overcomes the peaked and decreasing gas pressure. The strength of the recoil spring and the mass of the bolt also play into the equation because as the bolt blows open pressure is rapidly released out the back of the chamber too. By the way, I recently stayed at a Holiday Inn Express. |
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