I'm not asking out of ignorance.  Quite frankly I think a 1/9 barrel would be just fine for me, BUT, as with any arfcommer I try to think ahead in the event TSHTF.  So, can anyone tell me about how much a steel-cored or even DU round of 5.56 weighs?

edit:  I don't think there are any steel-cored 5.56 rounds are there?

I'm thinking of purchasing this barrel from Bushmaster:
www.bushmaster.com/products.asp?cat=7
A BBL-20A2A

I don't suppose anyone else has used this barrel and could give some comments about it?

use the 1:9 and don't look back.   another thread is running about this issue currently

1/9 is great for everyone. no problems with it. 1/7 is just that little extra that is nice to have but not absolutly neccesary.

Sorry to be the dissenting voice here - but the 1/7 twist is my choice as it allows the use of mil-surplus 55grn M193 and 62grn M855 as well has having the capability of firing the newer more lethal at extended ranges 75grn and 77grn rounds.

No brainer IMO, but then somefolks, it seems, prefer to stick with puny'er original rat gun weighted rounds - despite the added benefit of an available 1/7 twist rate which adds versitility to the AR platform.

Don't make any sense to me.

mike

1/7

Buy a 1/8 . That's the middle of the road if your not sure and will handle the heavy projectiles too. The Bushmaster DCM rifle is a gtg in my book regarding a complete package / rifle with warranty & bang for the buck. I know it's a bit more money but they are accurate.

Quoted: Sorry to be the dissenting voice here - but the 1/7 twist is my choice as it allows the use of mil-surplus 55grn M193 and 62grn M855 as well has having the capability of firing the newer more lethal at extanded ranges 75grn and 77grn rounds. No brainer IMO, but then somefolks, it seems, prefer to stick with puny'er original rat gun weighted rounds - despite the added benefit of an available 1/7 twist rate which adds versitility to the AR platform. Don't make any sense to me. mike

according to most target grade 223 rifles....you do not need 1:7 to stabilize 75 and 77 grain bullets.   that is only a milspec induced Myth

Strickly my experiance-

My 1/9's out perform my 1/8's by just a little.

Both are capable of accuracy greater than my shooting skillzzz.


Just my .02  

Squig-

Quoted: Quoted: Sorry to be the dissenting voice here - but the 1/7 twist is my choice as it allows the use of mil-surplus 55grn M193 and 62grn M855 as well has having the capability of firing the newer more lethal at extanded ranges 75grn and 77grn rounds. No brainer IMO, but then somefolks, it seems, prefer to stick with puny'er original rat gun weighted rounds - despite the added benefit of an available 1/7 twist rate which adds versitility to the AR platform. Don't make any sense to me. mike according to most target grade 223 rifles....you do not need 1:7 to stabilize 75 and 77 grain bullets.   that is only a milspec induced Myth

Are you talking from experience or just furthering a myth on your side of the argument?  I personally have shot 77 grains at 60 yards from a 1/9 and not found it to be lacking.  But, that is not very far and distance as well as length of barrel could change that.  Some people on this board have had the heavier bullets not stabilize with a 1/9 barrel.  You seem to be pretty convinced yet have little experience.  

If 1/7 is preferred by the Army, then 1/7 is for me.

Quoted: according to most target grade 223 rifles....you do not need 1:7 to stabilize 75 and 77 grain bullets.   that is only a milspec induced Myth

Without getting too technical here the OP asked a specific question about TWO twist rates.

As my SHTF and goto "carbines" are 14.5" w/ permFS and 16" barrels which are mil-spec 4150 steel and chrome lined - I want MINE in the easiest to obtain 1 in 7 twist.

Why you ask? (not that 1/8 won't stabilize the 75 & 77 grn bullets, it will in most cases, but the OP didn't ask about that twist rate and "it" normally comes as chrome-moly or stainless steel - not 4150 chrome lined)

My primary weapon is a LMT M4 14.5" w/ perm G6 pitching 77grn Black Hills (blue or red box) ammunition. It is KAC RAS II and Aimpoint equipped and zeroed using the 50 yard Santose IBZ zeroing method and because I have easy and regular access to an 800 yard range off dad's back porch I have fired this M4 on many occassions well past the normal considered "practical" range for a M4 AR. Using a hold-over based on the avarage human I can regularly and consistently, provided the loose nut between the seat and the steering wheel does "his" part properly, get mid-torso hits at 700 yards from my M4.

I also have an ACOG TA01NSN equipped BCM (Bravo Comany Machine) M4, 14.5" w/ perm Phantom which using the very same fodder can and easily obtains the same results (using the less guesstimated hold-over thanks to the 600 yard BDC line of the ACOG) at 700 yards.

What person in the proper frame of mind don't want a rifle in his hands capable of centermass hits from 10 foot to 700 yards?, (with a little practice that is)

You'd be hard pressed to get this kind of results from a 1/9 carbine, believe me I have tried for at one time all my carbines were 1/9 twist...., (I upgraded and I did it for a specific reason)

mike

While I do not have access to an 800yd range I will say that the 1:9 barrel on my 16" will shoot 69gr bullets well enough at 383yds (far as i can shoot in my backyard) to give anyone an extremely bad day.

This is a topic i absolutely AGONIZED over when doing my first build. Honestly i made way to big of a deal out of it. My thinking behind getting the 1:9 was this

a. Most of the bullets i shoot will be in the 55gr or so range. If i want to step up a little (see above) the 1:9 should do fine unless i go with the real heavyweights.

b. I absolutely could not postulate a situation in which i would be firing at a human target at distances exceeding 300yds. Even if SHTF. If i have to that's what i have the .308 for. If i shoot that far chances are it will be at a groundhog or paper target in which case the terminal effect of the 75gr+ bullets is largely unimportant.

c. All things being equal a 1:7 barrel will wear out faster than a 1:9. Most people will never notice this but i shoot ALOT.

I like the 1/7 barrels.  They have shot everything I have put through it.  From 45 gr to 77 gr.

A 1/7 can do anything a 1/9 can do and then some

Quoted: Buy a 1/8 . That's the middle of the road if your not sure and will handle the heavy projectiles too. The Bushmaster DCM rifle is a gtg in my book regarding a complete package / rifle with warranty & bang for the buck. I know it's a bit more money but they are accurate.

1/8 are for target type AR15`s

hard to find a M4 with a 1/8 twist