Hi All, I'm trying to decide which barrel twist rate would be most useful for a basic defense carbine. ( CQB, out to approx. 400 Meters or so ) I've recently retired my COLT 6520 in favor of my COLT 6721, as I have always felt that a heavy barrel AR-15 style carbine will stand up to much greater rapid / sustained fire than the lighter bbl'd version. Even though both weapons are semi-auto only, you can still manage to get that barrel very hot during moderate to heavy rapid fire use. As my 6721 has the 1/9 twist, I'm interested in determining which specific projectile weight(s) it should prefer. As a rule, I tend to like the BH 77 gr. loads, but the Hornandy 75 gr. TAP load should also work well. Any tips or comments will be very much appreciated. THANKS,      dpast32

Quoted: Hi All, I'm trying to decide which barrel twist rate would be most useful for a basic defense carbine.

1:7 as it allows you to use the best of the defensive loads.

I've recently retired my COLT 6520 in favor of my COLT 6721, as I have always felt that a heavy barrel AR-15 style carbine will stand up to much greater rapid / sustained fire than the lighter bbl'd version.

 Are you planning on getting into hours long firefights where you'll need to shoot 1000s of rounds at a sitting?

The thinner barrels did (and do) work just fine for the military, and you'll find they are easier to handle with one hand (should your other one be hurt or need to do somethine else).

As a rule, I tend to like the BH 77 gr. loads, but the Hornandy 75 gr. TAP load should also work well. Any tips or comments will be very much appreciated. THANKS,      dpast32

The 75gr TAP and 75gr BH loads have better terminal performance than the 77gr SMK that is used in the 77gr Black Hills loads. (Unless you were a part of the special Georgia Precision Mk262 buy where they were custom made with the 77gr Nosler OTMs).\

Will the heavier loads work in your 1:9?  Only you know.  They are hit or miss - we ran a poll and it looks like roughly 50% of the 1:9 twist barrels will stabilize the heavy OTMs.  Clean the barrel thoroughly (including copper remover) then try it out.

If building from scratch I'd go with 1-7 but since you already have a 1-9 I'd run with it.  If it won't shoot 75s and 77s it will shoot 68s and 69s.

I would not sell a perfectly good barrel just to get 1/7 twist rate. As mentioned before, you can shoot 68s and 69s and try the 75-77s just to see if it will.

I have a 20" 1:9 that shoots 75's just fine.  Hell, Hornady even marks their 75 gr bullets as "for use with 1:9 twist".

To me 1:9 is a more useful twist.  YMMV.

- AG

Quoted: Hi All, I'm trying to decide which barrel twist rate would be most useful for a basic defense carbine. ( CQB, out to approx. 400 Meters or so )

If you shoot someone at 400m its not defense it's murder and any prosecuting attorney will make you out to be a "sniper". Guarantee you you'll get the lethal injection.

Go for a pump 12 gauge and a .38 sp w/Glasers if you want something for basic defense.

I am not trying to be an asshole, but you (along with about 10,000 other people on this board) may want to rethink exactly what you will be using your rifle for. I have no problem with people dressing it up or micro-analyzing bullet weight vs. barrel length vs twist rate, etc...

It's fun but will this be a range rifle? Off the bench? Is this going to be riding in a vehicle with you? Is this for home defense? Do you own a lot of property? Is this for 3-gun?

Sometimes if you just ask yourself a bunch of questions and then answer them, the solution presents itself.

i want to shoot 400m becuse one day we might need a civil unrest weapon like if some terriorist lets off a nuclear weapon or two are our economy collapes better to have the ability and not need it then need it and not have it.

Quoted: Quoted: Hi All, I'm trying to decide which barrel twist rate would be most useful for a basic defense carbine. ( CQB, out to approx. 400 Meters or so ) If you shoot someone at 400m its not defense it's murder and any prosecuting attorney will make you out to be a "sniper". Guarantee you you'll get the lethal injection. Go for a pump 12 gauge and a .38 sp w/Glasers if you want something for basic defense. I am not trying to be an asshole, but you (along with about 10,000 other people on this board) may want to rethink exactly what you will be using your rifle for. I have no problem with people dressing it up or micro-analyzing bullet weight vs. barrel length vs twist rate, etc... It's fun but will this be a range rifle? Off the bench? Is this going to be riding in a vehicle with you? Is this for home defense? Do you own a lot of property? Is this for 3-gun? Sometimes if you just ask yourself a bunch of questions and then answer them, the solution presents itself.

Quoted: ...a .38 sp w/Glasers if you want something for basic defense....

I don't think you could come up with a worse suggestion for a home defense weapon.

Ok maybe an Airsoft toy... (no joke one Airsoft company reccomends their product for home defense).

Quoted: Hi All, I'm trying to decide which barrel twist rate would be most useful for a basic defense carbine. ( CQB, out to approx. 400 Meters or so ) I've recently retired my COLT 6520 in favor of my COLT 6721, as I have always felt that a heavy barrel AR-15 style carbine will stand up to much greater rapid / sustained fire than the lighter bbl'd version. Even though both weapons are semi-auto only, you can still manage to get that barrel very hot during moderate to heavy rapid fire use. As my 6721 has the 1/9 twist, I'm interested in determining which specific projectile weight(s) it should prefer. As a rule, I tend to like the BH 77 gr. loads, but the Hornandy 75 gr. TAP load should also work well. Any tips or comments will be very much appreciated. THANKS,      dpast32

Much to read; Ammo Oracle

Quoted: i want to shoot 400m becuse one day we might need a civil unrest weapon like if some terriorist lets off a nuclear weapon or two are our economy collapes better to have the ability and not need it then need it and not have it.

Ok.

Now that you clearly stated your reason for having the weapon we can address the proper set up for you.

There are many far more knowledgeable than I, but the general rules of thumb are that the heavier barrel is not needed. My suggestion would be to find out if your local PD or State Police uses an AR and get one just like theirs.

Then buy good ammo, USGI magazines, and practice!

Quoted: Then buy good ammo, USGI magazines, PROFESSIONAL TRAINING, and then practice!

fixed it for ya!

Quoted: Quoted: ...a .38 sp w/Glasers if you want something for basic defense.... I don't think you could come up with a worse suggestion for a home defense weapon. Ok maybe an Airsoft toy... (no joke one Airsoft company reccomends their product for home defense).

I happen to live in an apartment. A .38 sp w/Glasers will do just fine. My D-cell maglite can take care of the rest.

I see you left out the part where I said "AND" a 12 gauge pump. I wouldn't recommend 00 in an apartment, though.

Quoted: Quoted: Then buy good ammo, USGI magazines, PROFESSIONAL TRAINING, and then practice! fixed it for ya!

Couldn't agree more.

Quoted: Quoted: Quoted: ...a .38 sp w/Glasers if you want something for basic defense.... I don't think you could come up with a worse suggestion for a home defense weapon. Ok maybe an Airsoft toy... (no joke one Airsoft company reccomends their product for home defense). I happen to live in an apartment. A .38 sp w/Glasers will do just fine. My D-cell maglite can take care of the rest. I see you left out the part where I said "AND" a 12 gauge pump. I wouldn't recommend 00 in an apartment, though.

Against what?  A malnurished ethiopean child?  Glasers are a serioulsy underperforming round and in a minimal caliber makes it even worse.  The .357 Mag version only penetrates 4.7", the .38 would be even worse.  Not something I'd bet the life of my cat on - let alove the my own life and that of my family.

Against what?  A malnurished ethiopean child?  Glasers are a serioulsy underperforming round and in a minimal caliber makes it even worse.  The .357 Mag version only penetrates 4.7", the .38 would be even worse.  Not something I'd bet the life of my cat on - let alove the my own life and that of my family.

Ok, it's really easy to see what direction this is headed in.

I take back my earlier statement about the 12 gauge and the .38 for home defense.

When multiple Tangos are making a forced entry into my apartment, I generally reach beside my bed and grab my trusty Colt LE6920 with my TA31RCO ACOG. I find that when employing the BAC in a low-light CQB situation this set-up does not washout when employing my Surefire and my red/green laser on my free-float rail system.

Naturally, I have a Troy BUIS in case my ACOG goes down.

Anyway, I like to use 62 gr. out of my USGI mags enhanced with MagPul followers. I would use the Black Hills but I am still doing calculations to see if my TA31RCO is actually calibrated to 62 grain out of a 16" or 14.5" 1:7 barrel.

I feel that I can get reliable explosive fragmentation at 7 feet out of a 16" barrel, so I don't have to worry about any rounds entering the neighbors apartment.

I know that my rig is not quite as nice as some others on this board, but remember, this is my basic defense carbine.

I have another that I am pimping out.

dpast32, sorry about the bum dope before; What the hell was I thinking? Everybody knows a 12 gauge shotgun isn't a manstopper. Especially in a CQB situation. A .38 as a backup is sheer insanity!

Thanks for making my mind right!

Quoted: Ok, it's really easy to see what direction this is headed in.

Obvioulsy you don't.  Nobody said a word about the 12 gauge - just your choice in ammo for the .38.  And instead of defending the selection with data, you go off on some rant.

Whatever.

Quoted: Against what?  A malnurished ethiopean child?  Glasers are a serioulsy underperforming round and in a minimal caliber makes it even worse.  The .357 Mag version only penetrates 4.7", the .38 would be even worse.  Not something I'd bet the life of my cat on - let alove the my own life and that of my family. Ok, it's really easy to see what direction this is headed in. I take back my earlier statement about the 12 gauge and the .38 for home defense. When multiple Tangos are making a forced entry into my apartment, I generally reach beside my bed and grab my trusty Colt LE6920 with my TA31RCO ACOG. I find that when employing the BAC in a low-light CQB situation this set-up does not washout when employing my Surefire and my red/green laser on my free-float rail system. Naturally, I have a Troy BUIS in case my ACOG goes down. Anyway, I like to use 62 gr. out of my USGI mags enhanced with MagPul followers. I would use the Black Hills but I am still doing calculations to see if my TA31RCO is actually calibrated to 62 grain out of a 16" or 14.5" 1:7 barrel. I feel that I can get reliable explosive fragmentation at 7 feet out of a 16" barrel, so I don't have to worry about any rounds entering the neighbors apartment. I know that my rig is not quite as nice as some others on this board, but remember, this is my basic defense carbine. I have another that I am pimping out. dpast32, sorry about the bum dope before; What the hell was I thinking? Everybody knows a 12 gauge shotgun isn't a manstopper. Especially in a CQB situation. A .38 as a backup is sheer insanity! Thanks for making my mind right!

while i don't agree with your non-sarcastic suggestions for ideal defense weapons, that is pretty damn funny.

1-7

Quoted: Quoted: Ok, it's really easy to see what direction this is headed in. Obvioulsy you don't.  Nobody said a word about the 12 gauge - just your choice in ammo for the .38.  And instead of defending the selection with data, you go off on some rant. Whatever.

I don't need to defend "the selection with data" as I stated that I live in an apartment. I do not want a round that will slice through thin adjoining walls and into the kid next door.

*sigh*

It's not ideal defense, its basic defense. This is what the guy posting the thread asked about. An AR is not basic defense, it is very, very advanced defense. I suggested a .38 revolver and a pump 12 gauge for basic defense. My birdshot and Glaser loads are tailored to my personal situation. He can do do some research and find the ammo that's right for him.

For advanced defense, if he wants to use the 77 gr 5.56mm loads then he should use a 1:7 twist, easy enough. It was later determined that he wanted this carbine to hedge his bets against civil unrest, so I suggested he get the same ARs that the cops use. If he wants it for "CQB, out to approx. 400 Meters or so" then a 16" 1:7 barrel should do him up just fine.

Quoted: My birdshot and Glaser loads are tailored to my personal situation.

Not again.  

Quoted: Quoted: My birdshot and Glaser loads are tailored to my personal situation. Not again.

At least he will never be tried for murder with that set-up.

Quoted: Quoted: My birdshot and Glaser loads are tailored to my personal situation. Not again.

Oh grievous sin... I mean my "12 gauge load other than 00 buckshot low impulse tactical". Birdshot is a slang term. But I know that everything on the AR side is over-analyzed into extinction.

Want to see a pic of my M4gery?! Get both!!

.38 is a good choice. .38 Glasers is a very bad choice. This isn't mall-ninja stuff, its common sense. If a bullet can't reach a blood-bearing organ, it does superficial (albeit painful) damage. Just like if a knife point just breaks the skin, it won't cause lethal damage.

FYI, I use a Colt .38 OM with either 158gr. Hornady JHPs, and a 12 gauge 870 for HD.

Uh , back to original topic! The longer barrels can get away with less twist. My 24 will handle 77's just fine.  The 14's need the fast twist, but I would not get rid of a 1 in 9 if that is what I had. SHoot it and you might be surprised.

Not too knock anyones choice in a home defense firearm Im gonna say this,what evevr you use learn to use it well and learn it thouroughly so you can manipulate its controls in the dark or with out looking,second any fire arm is better than none at all.If I leave out my 12 ga. for the home I use #4 shot so I dont have to worry about over penetration even though the ceiling is my only worry because Im on the ground floor and no apartments to my left or right just other buildings.Primarily I keep out my 1911 and leave the ARs and other rifles out of the mix although I can get to them easily if need be.I have both a 1/7 and 1/9.I got the 1/7 specificaly for heavier bullets past 69 grain with the intention of using that carbine as a light weight medium range sniper rifle..evevr since tears of the sun with the seal up in the tree sniping with a silenced carbine I see the value of ARs being able to handle multiple tasks.So for all practical purposes and ranges normaly encountered 1/9 is fine..if you want more range with heavier bullets and are going to employ a carbine as a medium range sniper then go 1/7...if I could only have 1 carbine I would go 1/7..if you can get both.