Quote:
Originally Posted by R.W.Dale
I have read that the twist rested on the m&p 15/22 is slightly faster than the saami standard 1-16" twist. This appears to be supported by the fact that even as far out as 100yds my 15/22 will shoot feed and most importantly group with aguila's 60g sss load with no signs of keyholing evident.
As to the comments about twist rate above they are by in large incorrect. Bullet weight is only one factor in bullet stability bullet LENGTH is much more important. A short blunt 60g bullet can be stabilized quite effectively from a 1-14 twist as is the case with the old sierra smp from a 22/250, with a soft lead 22lr bullet being even shorter needing even less twist.
This group was fired at 100yds, I fired two such groups but the first one and smaller of the pair landed on my backer and not on the plate where I wanted it so its not shown.
This said I would be reluctant to shoot too many of these as the bolt velocity"felt" much faster than 36 or 40 g high velocity loads.
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The correct twist rate for Aguila 60g SSS is 1:9. Not very close to the 15-22's 1:15.6. It is also the longest bullet made in .22LR, requiring the short CCI-Stinger case if I am not mistaken. I have some myself and also experimented with them in the past. Since my AR15-22 is the PC model and has a match chamber I won't shoot them out of that or my Remington 597 with its match chambered Volquartsen CF bull barrel. Since the 60g SSS is about the same length as a 55-62g .223, and the standard AR is also a 1:9 twist you are correct that the issue is bullet length. The best platform to shoot them out of, short of a a custom 1:9 twist barrel (you can get 10/22 barrels in this twist rate) is any standard AR rifle with a CMMG/Ceiner/Stag .22 conversion (not a dedicated upper because those all have 1:16 in them) so you can use the twist rate of the AR barrel (1:7 to 1:9). Shooting them out of a barrel with a 1:14 twist is incorrect by any accuracy standard, period. That does not mean that you might not have conditions that would produce no external forces on the bullet so as to have no random longitudinal rotation. In otherwords you might luck out for a few groups. My own experience is that out to 100 yards, under normal circumstances, you can expect defections from keyholing to hit around 20% of the time, on average.