i have a question and i am sure people will get way too technical for me but which rate of twist would be better in a 16inch ar barrel 1 in 9 or 1 in 8. i will be shooting store bought ammo if that helps.

It's the weight of the bullets you'll be shooting that matters, not the length of the barrel. 1 in 8 is much more versatile than 1 in 9. With a 1 in 9 twist, you'll be limited to 55 gr or a tad heavier. 1 in 8 will handle the heavier bullets from 69 on up to 77 gr. It'll also handle the lighter 55 gr bullets. If you're only going to shoot the heavyweight bullets, a 1 in 7 would be better still.

thank you. perfect answer in laymans terms

Spot on

Fully agree with the above comments. With a 1-8 or faster and factory loads try the 75gr TAP loads. Some 1-9 will do ok with them but 1-8 or faster should be great with them. My SIG 556 works well with them and its 1-7, I am going to push the envelope this summer a littls and see if can get the 90gr Berger bullets to shoot well out of it.

I never understood the need for a 7 or 8 twist with a 16" barrel. People shoot the heavy bullets to gain the potential of their high ballistic coefficients but with such a short barrel and reduced velocities you never get there anyway. All 3 of my 9 twist barrels shoot 70gr Berger VLDs very well.

I agree for the most part 30378. He said he would be shooting store bought ammo and that pretty much means the lighter stuff. The military decided years ago that the 1:9 was plenty good for up to 69 grain. The M4 went to 1:7 because of the poor stopping performance of the SS109 type bullets. IMHO chamber and barrel type make a lot more difference unless you're going to rifle length barrels and things like High Power Matches where the 75gr and on up bullets rule. In reality a lot of the barrels listed as 1:7 and 1:8 are really 1:7.7 the excellent Kreiger's being a prime example.

I'm adding this to my favorite topics list. Good info in a quick and concise manner that all us "non-tech" gun guys can understand. My vote for post of the year! Thanks!

Good point. The only reason I do though is for 75-77 grain OTM ammo. I find it to be excellent for hunting. Most people won't shoot heavy match ammo, so a 1/9 in smarter for most people.

I definately appreciate the info you guys are posting. and yes one poster was correct that it will be the lighter weight bullets. i think that 55 grain is common. i have zero intentions of reloading bullets and or paying extreme prices to buy custom reloaded bullets.
one poster put that the 1 in 8 barrel will handle heavier loads but what about the lighter 55 grain loads. I am thinking from what i am reading from you guys is that either the 1 in 8 and 1 in 9 will handle the 55 grains bullets about the same. am i correct

Go wit faster twist you can't overspin a bullet imo

works for me. thank you

Another point to consider. If you ever do get into handloading, the 7 and 8 twist barrels build pressure faster with all weight bullets. You can drive a 55 grainer at much faster velocity from a 12 or 14 twist than a 7 or 8 twist. All twist gives you is added stability for heavier or longer length projectiles.

A 1:9 twist is very versatile, and only excludes the use of most bullets 75gr or heavier. For the shooter using mid-weight bullets only (55gr-ish), the 9 twist is a great choice in an AR.

My Colt 1:9 performs admirably with both 69 and 53 Sierra MK's.

Twist refers to length of bullet.
The heavier, the longer in a given calibre.

http://kwk.us/twist.html
http://www.border-barrels.com/barrel_twist.htm

You can drive a bullet to fast, FPS in a fast twist and the bullet will disintegrate in flight.

People thought they were missing the target, bullets were not making it to the target.

My 1:9 shoots a 64 grain pretty well.

Actually, the M16A2 went to 1 in 7 twist because of the M249 machine gun.

They wanted to keep long range terminal performance, and adopted the SS109 bullet (M855/M856 tracer) and decided since they were revamping the M16 anyways, to keep the ammo commonality in weight and twist.

The SS109 was developed to work specifically with the 20" barrel and zip through Soviet body armor then we spent 25 years shooting skinny guys in man dresses without armor so the round sails through and keeps going especially in short-barreled carbines.

I prefer 1/7 and heavier bullets, currently using a 1/9 and sticking with 55gr because when i got back from overseas the post election buying frenzy left me few choices.

55gr still works fine, half the world still uses M193.

I said M4 and not A2. Interestingly it was the USAF that led the way in the M4 development and should have been listened to from the beginning. The first M4's extending through Desert Storm were non-standardized and there were a number of variations depending upon the manufacturer as well as the customer. Bushmaster in particular sent large numbers to Kuwait which were 1:9 barrels. I believe many of these were converted to 1:7 and sometimes they can be identified as looking like "parts guns."The IDF and various other countries had them in quantities along with SF's from here and other countries. With the apparent failure of the Galil the Israeli's were very interested in this weapon before going on to develop the Tabor and were the first to identify some of the problems with the SS109 and the shorter, faster twist barrels. It's my understanding that they secretly manufactured lots of HP rounds sold by IMI to solve this problem ( illegal by international standards). This might be true because for a number of years these were available as "match" HP's in the surplus market. It's also my understanding that the rifle twist controversy continued quite well into the 90's before the Army took over and finally said 1:7 with the current ammunition, but still allowed a number of manufacturers to provide small numbers of carbines of various configurations for evaluation. Of exceeding interest is that both Bushmaster and Colt pushed hard for a 1:9 twist in the M4 but Army Ordinance overruled.
BTW you AF guys are shooters. When I was going to High Power Matches one of the biggest questions was "are the AF guys going to be there because I'd like to have a chance of winning." Rule#1 of High Power. Never compete less than a hundred miles from an AF base unless you want to be embarrassed.

me before the guestion

me after a few people answered

my fellow THF members

me now

Nah, it's just fun to discuss and get other people's perspective. V6B has a very good one and was actually there using the weapon. In short, for you, the 1:9 barrel is perfectly adequate, especially with the ammunition availability out there. My personal opinion is that one day the AR and its magazines will to be simply put illegal to even possess. If the Kenyan is re-elected you can be sure he will try. If he can get back a Democratic/Communist/Socialist Congress he will. I think if you're to have an AR you'll want one where you already have a lot of ammunition. I'd include a few spare parts in there as well.

So, my 1:9 twist 14.5" Bushmaster barrel should be good with 62 grain bullets?

It should do just fine.

Agreed. Just don't shoot heavier than about 65's in a 1/9 they'll usually have stabilization problems.

I have some 77gr Mk 262's that accuracy-wise are short range only. But if my Deep Deep Crap box gets opened the range will be very short indeed.

1/9 does fine on about 45-65gr, 1/8 handles everything from 40-77ish and 1/7 62-heavier, though under 150m will shoot 55's pretty well. I've shot M193 (55gr) out of M16A2's that far with no issues, as well as older 55gr tracers out of M4's.

I love the ballistic gel on those 75gr Hornady TAPs



Oh excuse me intruder, was that your chest cavity?

that looks like the inside of osama's head