Originally Posted by bsa1917hunter
Originally Posted by kwg020
It's my understanding that when the M16A2 was being developed it was planned for a 1/9 twist to shoot the 62 grain FMJ bullets. The problem was for the tracers. They were longer but lighter because they were hollow for the phosphorus compound that would light as the powder burned. To be accurate it needed a 1/7 twist to be accurate.

Due to a miss communication all barrels in the M16A2 became 1/7 twists. If it wasn't for that mix up there would be no 1/7 twist barrels or there would be very few of them and they would be highly specialized. This information came directly from a fellow who was involved in the development of the M16A2 while he was active duty Army. As it appears, the 1/7 twist is a really great twist for the shorter (14.5") M4 barrels. I guess you could call it a "happy accident".

I have a 1/12 twist Remington that really shoots the light weight bullets very well but at 60 grains the accuracy starts to fall off. I have not tried a 62 grain bullet in it. I just don't see the logic. Do I wish it was a 1/9 twist ? You bet, but I can make the 52's and 55's work. I have a Ruger American and some AR's for anything heavier than 60 grains. I understand the new Remington's in .223 are now 1/8 twist. I think that is a good choice for an all around rifle. The exceptions would be for the super light and the super heavy bullets.

This has been a great discussion.

kwg

Cool info about the A2 kwg. Thanks for sharing. I think the main thing here to take away from the thread is use the appropriate bullet for the rifle you are shooting. It doesn't have to be an argument, like some guys want to make it. I also agree with you that the 1 in 8" is damn near perfect. Couple that to a damn good rifle like a Tikka CTR and you are going to be in hog heaven.

There is a fellow on AR15.com that goes by the name Cold Blue. He was part of the M16A2 development program. He was telling us about the decision on the barrel twist. The original design called for a 1/9 twist but there was some discussion about the accuracy of the tracers and they learned the tracer needed a 1/7 twist to be accurate. Anyway, when the barrel makers asked about the barrel twist someone gave the 1/7 number not knowing the team was going with the 1/9 as per the design. The barrels came back from the makers 1/7's.

They liked the results and kept the 1/7 twist for the 62 grain bullets in the M2. It was later determined that the shorter M4's had better long distance accuracy with 1/7 twist at the reduced velocities with the shorter barrels. I gathered from the conversation the heavier bullets came later to make the best of the new fast twist. It appears the Army Marksmanship Unit and the Navy both wanted heavier and more stable bullets. We know the results as the MK-262 made by Black Hills Ammunition.
https://www.shootingtimes.com/edito...ns-black-hills-mk-262-mod-1-review/99098

It also appears that the Army's DMR's (Designated Marksman Rifle) went from the 1/7 chrome moly barrel to stainless 1/8 barrels.

Barrel: The 1:7 twist, 20-inch (510 mm) barrel from the M16A2 and A4 were replaced with a stainless steel Douglas Barrels 1:8 twist, 20-inch barrel, with 12 flutes cut into the barrel to reduce weight. The front sight block was installed with 4 set screws instead of two taper pins. The SDM-R retained the A2-style flash hider.

https://en.wikipedia.org/wiki/Squad_Designated_Marksman_Rifle

kwg

For liberals and anarchists, power and control is opium, selling envy is the fastest and easiest way to get it. TRR. American conservative. Never trust a white liberal. Malcom X Current NRA member.