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Started By
Message
1
Posted on 11/13/23 at 7:49 am to DownshiftAndFloorIt
Can you shoot 55gr from 1:9 reliably?
Posted on 11/13/23 at 8:09 am to dstone12
Yes
Original twist for 55 grain was 1-12 as it promotes more tumbling and yawning for more damage.
Military changed to 1-9 when they started using 62 grain.
1-9 can shoot 55-69 gr
1-7 can shoot up to 77 gr
A few have a 1-8 twist but most are 1-9 or 1-7
Original twist for 55 grain was 1-12 as it promotes more tumbling and yawning for more damage.
Military changed to 1-9 when they started using 62 grain.
1-9 can shoot 55-69 gr
1-7 can shoot up to 77 gr
A few have a 1-8 twist but most are 1-9 or 1-7
This post was edited on 11/13/23 at 8:16 am
Posted on 11/13/23 at 9:03 am to jimbeaux82
Thank you
Posted on 11/13/23 at 7:29 pm to jimbeaux82
quote:
Military changed to 1-9 when they started using 62 grain.
Military changed to 1-7, they didn't adopt 1-9 because it had a hard time stabilizing tracer rounds.
Posted on 11/14/23 at 5:55 am to jimbeaux82
quote:
Original twist for 55 grain was 1-12 as it promotes more tumbling and yawning for more damage.
Military changed to 1-9 when they started using 62 grain.
1-9 can shoot 55-69 gr
1-7 can shoot up to 77 gr
A few have a 1-8 twist but most are 1-9 or 1-7
Good info for a newbie. I had no idea what 1-7 twist meant on my new AR.
Posted on 11/14/23 at 8:09 am to RetiredSaintsLsuFan
What 1-7 means is that the bullet will make one 360 deg rotation in 7 inches of barrrel due to the rifling in the barrel.
1-12 means it will make one rotation in 12 inches of barrel.
Therefore the smaller the number the faster the twist. The longer (therefore usually heavier) bullets require a faster twist to properly stabilize
1-12 means it will make one rotation in 12 inches of barrel.
Therefore the smaller the number the faster the twist. The longer (therefore usually heavier) bullets require a faster twist to properly stabilize
This post was edited on 11/14/23 at 8:12 am
Posted on 11/14/23 at 8:09 am to MetroAtlantaGatorFan
Military changed to 1-7
Thanks. I stand corrected
Thanks. I stand corrected
Posted on 11/14/23 at 8:12 am to RetiredSaintsLsuFan
quote:
Good info for a newbie. I had no idea what 1-7 twist meant on my new AR.
my 16" PSA barrel is 1:7 and shoots the M193 55gr very well...I zeroed the iron sights at 50 yards with no problems FYI....and that should be your range ammo of choice considering the price. I'd suggest 75 or 77 gr for defense or hogs. I also have some 223 55gr Federal which is supposedly made for deer hunting.
Posted on 11/14/23 at 8:17 am to The Levee
Most AR15’s today are made in a 1-7 twist.
Like you I routinely shoot 55 gr ammo thru mine with very acceptable accuracy.
Federal Fusion in 62 grain or any of the Barnes TSX loads 55-70 grain are about as good as you can get for deer and hog hunting loads in the 223/5.56 ammo
Like you I routinely shoot 55 gr ammo thru mine with very acceptable accuracy.
Federal Fusion in 62 grain or any of the Barnes TSX loads 55-70 grain are about as good as you can get for deer and hog hunting loads in the 223/5.56 ammo
Posted on 11/14/23 at 9:59 am to Shexter
quote:
Always stick to brass case. Steel in AR-15's is horrible.
No it is not. Steel in cheap AR's is horrible, and it is not because of the ammo.
Posted on 11/14/23 at 12:29 pm to Scoob
quote:
It shouldn't hurt the extractor, I've seen some studies and steel cases are actually softer on the Rockwell hardness scale than some brass.
What hurts the extractor (and the bolt) has nothing to do with material hardness here, and everything to do with case obduration in the chamber. Coated steel cases seal well but they can also "stick" a bit longer than a brass case as the steel takes slightly longer to shrink down as chamber pressure drops. This means the extractor is trying to yank back on a case that is still gripping the chamber more so than would brass cased ammo. The forces involved are in the high hundreds to thousands of pounds so even small differences in timing can have detrimental effects.
Posted on 11/14/23 at 12:35 pm to RetiredSaintsLsuFan
quote:
Good info for a newbie. I had no idea what 1-7 twist meant on my new AR.
Barrel length also matters, a 20" 1:9 twist barrel will stabilize M855A1 whereas a 16" 1:9 won't. My 10.5" pistol 1:7 won't stabilize M855A1 at all but will work with M855 all day.
Posted on 11/14/23 at 12:56 pm to Clames
I guess that's why USASOC is switching from 10.3" to 14.5" with a midlength gas system.
Royal Marine Commandos are being issued a 13.7" now from KAC but I'm not sure if they use M855A1.
So are operators still using Mk 262 or Mk 318?
Royal Marine Commandos are being issued a 13.7" now from KAC but I'm not sure if they use M855A1.
So are operators still using Mk 262 or Mk 318?
This post was edited on 11/14/23 at 1:05 pm
Posted on 11/14/23 at 1:12 pm to Clames
quote:
Barrel length also matters
I'm not refuting that it does matter, I never understood why it does though. Is it just the loss in MV and therefor RPM?
Posted on 11/14/23 at 2:30 pm to DownshiftAndFloorIt
Fragmentation threshold for M193 and M855 is roughly 130 yards with an M16 vs roughly 90 yards for an M4.
Posted on 11/14/23 at 3:07 pm to MetroAtlantaGatorFan
Due to speed loss?
Posted on 11/14/23 at 3:08 pm to DownshiftAndFloorIt
Posted on 11/15/23 at 3:27 pm to DownshiftAndFloorIt
quote:
Is it just the loss in MV and therefor RPM?
Yup. Faster the freedom pill goes, the faster it spins for any given twist rate. Also, that means it's faster to settle into its most stable flight which is why M16A2's had better and more consistent terminal performance than M4's with the same ammo.
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