Ideal Twist AR15
- Thread starter Fred J
- Start date
K
kgcoker
Guest
You will need 1 in 12 for the light bullets. 1 in 9 works great for 69 grain bullets. 1 in 7 for the heavier bullets.
This is my experience.
KG
This is my experience.
KG
R
rockthehorse
Guest
There are slight variations even in printed literature. Generally the slower the twist, then the heavier the bullet. Most feel that the 1-9 twist will stabilize both the 55 and 62 grain military loads. For me, IMHO, I shoot the 62 grain bullets in my 1-7 and 1-9 rifles, 55 grain bullets in my 1-9, 1-12 rifles and 1-14 rifle. I also have some 50 grain frangible bullets that I shoot through a 1-14 twist barrel. The 1-14 rifle is a class III, so I am not printing on paper with that one.
Talked with a shooting buddy about stabilizing bullets in his home defense "urban" AR-15. His comment to me was "why do I want to stabilize the bullet (for defense)? Point taken.
As others chime in, I think you will see that there certainly overlap. Scott
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mike in co
Guest
kg the mil shoots 62/64 from a 7 twist.
so lets back up...no such thing as an ideal twist in an ar15...till one limits bullet weight.
since the poster asked about 52 to 55 gr i would answer 12.....because some 55's have plastic tips and are longer.....and the 14 may not work for them.
a great compromise bbl on an ar15 is a 1/8 twist..it will shoot 55 thru 80's......i do not know about 52/53 match bullets.
chambers are always a compromise when you spread out the bullet weight and still want to load form a mag....( cant do this with 80's)
if my choice was a 1/7 or a 1/9 i would choose 1/9......but if either were chrome lined all bets are off on accuracy.
life is a compromise..........
if you want a very accurate, mag fed ar15 to shoot 52/55's/////well then gut a quality 12 twist with the correct chamber and throat for those two bullets......
mike in co
so lets back up...no such thing as an ideal twist in an ar15...till one limits bullet weight.
since the poster asked about 52 to 55 gr i would answer 12.....because some 55's have plastic tips and are longer.....and the 14 may not work for them.
a great compromise bbl on an ar15 is a 1/8 twist..it will shoot 55 thru 80's......i do not know about 52/53 match bullets.
chambers are always a compromise when you spread out the bullet weight and still want to load form a mag....( cant do this with 80's)
if my choice was a 1/7 or a 1/9 i would choose 1/9......but if either were chrome lined all bets are off on accuracy.
life is a compromise..........
if you want a very accurate, mag fed ar15 to shoot 52/55's/////well then gut a quality 12 twist with the correct chamber and throat for those two bullets......
mike in co
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Greg Culpepper
Guest
Fred
Fast twist barrels can deliver very good accuracy with short bullets. Slow twist barrels will not deliver accuracy with long bullets. My first AR was a 7" twist Colt HBGM with a chrome bore. The best I could get out of it with 69gr Sierras was around an inch which wasn't much much better than white box ammo. Later, a standard GM, also with a chrome bore acted the same. But with 52 gr Bergers they both thought they were a BR rifles. Go figure. I've had more 7's, 7.7's, 8's, 9's and a 10. Based on how well these "too fast" barrels shoot with a wide range of bullets, I wouldn't bother with anything slower than an 8" twist unless my intention was to shoot stubby bullets exclusively.
Greg
Fast twist barrels can deliver very good accuracy with short bullets. Slow twist barrels will not deliver accuracy with long bullets. My first AR was a 7" twist Colt HBGM with a chrome bore. The best I could get out of it with 69gr Sierras was around an inch which wasn't much much better than white box ammo. Later, a standard GM, also with a chrome bore acted the same. But with 52 gr Bergers they both thought they were a BR rifles. Go figure. I've had more 7's, 7.7's, 8's, 9's and a 10. Based on how well these "too fast" barrels shoot with a wide range of bullets, I wouldn't bother with anything slower than an 8" twist unless my intention was to shoot stubby bullets exclusively.
Greg
Because this is a public forum I feel this phrase need be clarified.... "Generally the slower the twist, then the heavier the bullet." The statement is not true on it's face.
I'm sure rockthehorse meant that HEAVIER or LONGER bullets require a FASTER twist...
al
R
rockthehorse
Guest
Al is absolutely correct...... I stand corrected!!!! Guess we officially call this thread the barrel and tongue twist thread!!!
victorpatrick
New member
hi
For a 55 grain or 52 grain .223 bullet in an AR-15, a 1:9 twist rate would be more suitable than a 1:7 twist rate.
The twist rate of a barrel refers to the rate at which the rifling inside the barrel rotates the bullet as it travels down the barrel. The twist rate is typically expressed as a ratio, such as 1:9 or 1:7, where the first number represents the complete rotation of the bullet in inches and the second number represents the barrel length required for that rotation.
rankdle
For a 55 grain or 52 grain .223 bullet in an AR-15, a 1:9 twist rate would be more suitable than a 1:7 twist rate.
The twist rate of a barrel refers to the rate at which the rifling inside the barrel rotates the bullet as it travels down the barrel. The twist rate is typically expressed as a ratio, such as 1:9 or 1:7, where the first number represents the complete rotation of the bullet in inches and the second number represents the barrel length required for that rotation.
rankdle
Asa Yam
New member
All,
Rifling twist and bullet weight are tied closely to the evolution of the AR-15 and M-16 rifles. I am quoting from Mike's post, because he seems to list so many.
There used to be an AR-15 magazine modified (designed?) to load 10x 80 grain rounds into the rifle. Think of a 20 round magazine, redesigned to feed 10 loads. Rounds were loaded at an angle (single stack) hence the "modified" statement. Note Sierra and Hornady's introductions of 75 and 77 grain bullets, designed to be magazine fed pretty much ended the market for magazine loaded 80s. Black Hills Mk 262 Mod 1 ammo, anyone? (Cannelured 77 grain Sierra, loaded with TAC for the US government.)
Probably true. Still, it might be surprising as to how accurate these bullets can be fired through a fast twist barrel. Now, if you are shooting a "Cooper Challenge", try shooting 77s out of a magazine. (Think of using a faster twist barrel if trying this.)
Rifling twist and bullet weight are tied closely to the evolution of the AR-15 and M-16 rifles. I am quoting from Mike's post, because he seems to list so many.
IIRC, plastic tipped 55s didn't become popular until the 1990s. The 1-14" twist disappeared on the AR-15 in the late 1950s/early 1960s, due to feedback from the US -Army's cold weather tests. The original 1-14" became the 1-12" of the M-16 rifle to keep 55 grain FMJBTs flying point-on in sub -40* F temperatures. Actually, there probably is a difference in length between a FMJBT and a HPBT (the HPBT being longer) to make a difference in accuracy.
Not the original intent of faster twist AR-15 barrels. Faster twists on M-16 rifles were introduced in the mid-1980s, due to the desire to shoot the longer tracer bullets introduced by the Belgians. (Shooting 62 grain FMJBTs was also a key issue in increasing the rifling twist of the M-16A2.) Just for historical purposes, I know of a few examples where 1-9" twist barrels will not shoot 77s accurately. (Perhaps due to a nonuniformity in a marginal twist?)
There used to be an AR-15 magazine modified (designed?) to load 10x 80 grain rounds into the rifle. Think of a 20 round magazine, redesigned to feed 10 loads. Rounds were loaded at an angle (single stack) hence the "modified" statement. Note Sierra and Hornady's introductions of 75 and 77 grain bullets, designed to be magazine fed pretty much ended the market for magazine loaded 80s. Black Hills Mk 262 Mod 1 ammo, anyone? (Cannelured 77 grain Sierra, loaded with TAC for the US government.)
Probably true. Still, it might be surprising as to how accurate these bullets can be fired through a fast twist barrel. Now, if you are shooting a "Cooper Challenge", try shooting 77s out of a magazine. (Think of using a faster twist barrel if trying this.)
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Asa Yam
New member
Not every chamber for 80s is a Colt or a Wylde, there are others. I stand by my statement, there IS at least ONE magazine designed to load and feed 80 grain loads.
rsmithsr,
Asa is CORRECT.
20rd mags were used w/ 77 & 80gr loads staggered kitty corner in the mid to late 90's to run in NRA Nat'l & CMP EEIC Matches.
Derek Martin-Accuracy Speaks- was the instigator if memory serves me correctly.
Asa Yam
New member
I did not say it was a 20 round mag. I said
There was a magazine produced by an independent, then picked up by DPMS, that could shoot that load from the magazine; a modified bolt catch was also required. Externally they appeared to be standard 20-round magazines, but they only held 8 rounds in a single stack; the case heads ride in the rib, thus allowing the increased length. They were originally targeted at NRA/CMP Highpower competition, but never really caught on (no marketing effort) and disappeared from the market. I treasure mine and continue to use them 20 years after I bought them. Match Rifle shooters moved to a variety of 6 mm and 6.5 mm rounds that offered better performance, but Service Rifle shooters could still benefit since they must maintain the external appearance of an as-issued weapon.