Is 1 in 7 twist too fast ...

F

foxC

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Full Member
Minuteman
Mar 14, 2013
38
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New York
#1
... for an AR15 twenty inch barrel using 55 gr bullets?

I just replaced a 16" 1:9 barrel with a 20" 1:7 and have a few spam cans of 55 grain lying around. Just wanted to know if the 1:7 twist rate is too fast for these pills.

Will 62 gr green tips work with this barrel or should I consider going heavier? TIA
 
#3
You won't hurt anything. I'm assuming because it's a spam can it won't be the most accurate stuff anyways.

IIRC (Mind you, my knowledge of the history of the M16 platform is a bit fuzzy), when the military switched to the M16a2, they bumped the twist to 1:7". I'm almost certain that at some point old M193 was used for training in 1:7 barrels. Never heard any horror stories.
 
#6
55gr V-Max bullets have shot lights out to 300-400yds in the 1:7's I've had - multiple 16" and 20" barrels. Nosler 55gr ballistic tips as well. YMMV.

Bulk mil spec 55's and 62's tend to shoot poorly in any AR barrel regardless of twist.
 
#8
Your spam ammo will probably not be accurate, but the twist won't be the culprit. Good handloads tailored to the gun with 55gr or 62gr bullets (NOT surplus FMJ) will amaze you with their accuracy.
 
#9
Only bullets you'll definitely want to stay away from are any of the thin-jacket varmint numbers; eg - Speer TNT, Sierra Blitz, Hornady SX, etc. I also tried running some Win 62PSPs through one of my Colt 1-7 ARs years ago - my spotter had lots of fun telling me where they hit the backstop (generally speaking, the ones that didn't blow up before reaching the target were hitting all over a 10'-12' area).

OTOH - Nosler & Sierra 77BTHPs have always hammered out of my 1-7tw ARs; also, when seated for single-loaded (non-magazine) use, 80 & 90gr VLDs shoot very well at 600+yds out of my 7-twist bbls.
 
#10
As has been pointed out the spam can ammo isn't going to help you win a National Championship, however; if I understand your question, will the 1-7 shoot those weight projectiles well, Hell yes- with good loads. Those that put out stupidity such as, "You need to shoot at least a 69gr, or your rifle won't shoot etc"., are just full of crap. As mtrmn pointed out, 52gr projectiles often shoot very well from a 1-7, Good luck!
 
#11
Graham said:
No worries. 55gr and 62gr shoot like shit anyway.
Click to expand...
Hilarious Graham!

He is absolutely right though. That is junk ammo anyway. Try some FGMM 69gr. in that barrel and you will be happy if it's a well put together rifle. Each rifle has ammo it likes and don't like. You just need to try and find what yours likes. Start with 69 gr FGMM if it don't shoot that well then your probably in trouble, but try some other heavier stuff and hopefully you will find your barrel a round it likes.
 
#13
If you try a heavier bullet a great alternative to Federal GMM is Fiocchi Exacta. Both come loaded with either the 69 or 77 SMK. Both shoot equally as well out of my JP 20" 1/8. Fiocchi is $19 a box vs 29 a box for FGMM in the Phoenix area.
 
#14
I shot some varmint 45 gr 223 out of my Daniels Defense 1/7. Grouped just above 1 moa at 100 yards. I had never ran anything lighter than 55 through it before that. Surprised me how well it shot. Got it for Xmas from someone who doesn't know any better. Ironically joke was on me.
 
#16
If your reply is to me I typically only shoot 75 and 77 gr through it I load all my own for it. I just simply wanted to burn through the Xmas present. I even hit the large gong 10" at 300 yards with those factory 45 gr bullets.
 
#17
svxwilson said:
If your reply is to me I typically only shoot 75 and 77 gr through it I load all my own for it. I just simply wanted to burn through the Xmas present. I even hit the large gong 10" at 300 yards with those factory 45 gr bullets.
Click to expand...

If anything you will realize that you will have fire formed brass for your AR to reload if your into it. The mantra I have been taught is consistency is the basis for accuracy . This is only going to happen with either match or hand loads. I would do a load development for your rifle and see what it likes with 70+ gr and go from there.
 
#18
As stated above , bulk/surplus 55's and 62's are not going to win any benchrest competitions, but they may pleasantly surprise you. I have seen lots of xm-855 shoot just over an inch at 100 and lots of 55's not far behind more than once or twice. Bench it, shoot it, and then blast away as needed after you know what it does in your particular rifle. Even 2moa ammo is quite good enough to bang steel plates out to a few hundred yards, and since most people shoot on a 100yd range, it does what 90% or more of the shooters will ask of it.
 
#20
"As stated above , bulk/surplus 55's and 62's are not going to win any benchrest competitions, but they may pleasantly surprise you. I have seen lots of xm-855 shoot just over an inch at 100 and lots of 55's not far behind more than once or twice."


This^^^^^^^. I see the same, 1-1.5 MOA with my LC XM rds in 55 & 62gr through Colt, Daniel Defense, S&W, Bushy, etc. in 1:7 and 1:9 from 14.5" to 20" bbls further than 100yds.

OP, you shouldn't have any projectile issues with 55FMJBT through your 1:7 barrel.

Enjoy,
Keith
 
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