AR Sponsor
Posted: 10/3/2015 9:57:10 PM EDT
|
Easy question...I hope. When did they switch the twist rate from 1 in 12? And did it switch to 1 in 9?
Doc |
|
Quoted:
Easy question...I hope. When did they switch the twist rate from 1 in 12? And did it switch to 1 in 9? Doc The U.S. military never did use 1/9 twist barrels. The change from 1/12 to 1/7 came about with the adoption of the M16A2, which was 1986, I think. 
|
|
It starts in Belgium with the Minimi... Before NATO standardization of 5.56x45mm.
1:9 was the original idea for the SS109 round, and this twist works just fine for it. 1:7 came about because it was needed to stabilize the L110 tracer in arctic conditions. The Army decided that they weren't going to have a rifle that couldn't shoot both the ball and the tracer accurately under all conditions, so 1:9 never made it past discussion. |
|
The Black Rifle II states the A2 was developed FOR (at the request of) the Marines as they didn't have oodles of M16's like the Army. add the adoption of the (yuk) NATO M855 and I'd say the change happened with the introduction of the A2. Marines got them first (THERE'S a miracle!) then by default everyone else as needed. (Wiki says Marines '83 and Army '86} |
|
My tank unit had them in '88 when I arrived and had only just turned in their M60A3 (TTS) for M1(IP).
1st Infantry Division (Forward) might have had more priority than stateside units, but there were enough going around that even lowly tankers got one per tank. |
|
Quoted:
165,571 rpm's............approx., based on a velocity of 3,200 fps. Quoted:
Quoted: While we're on the twist rate change:
What was the rotational speed of the bullet in RPM of the pre-M193 ammo shot from the 1:14" twist bbl of the original M-16?  165,571 rpm's............approx., based on a velocity of 3,200 fps. Thought the pre-M193 ammo was a bit slower than M193? |
|
Quoted:
Thought the pre-M193 ammo was a bit slower than M193? Quoted:
Quoted:
Quoted: While we're on the twist rate change:
What was the rotational speed of the bullet in RPM of the pre-M193 ammo shot from the 1:14" twist bbl of the original M-16? 165,571 rpm's............approx., based on a velocity of 3,200 fps. Thought the pre-M193 ammo was a bit slower than M193? Might be............I dunno. That's why I stated @3200 fps. Maybe I should have stated it as such: ( velocity X 60 ) divided by 1.166666666666 = rpm's rpm's at a velocity of 3000 would be 154,285 rpm's..........or there a bouts. |
|
Quoted: Might be............I dunno. That's why I stated @3200 fps.
Maybe I should have stated it as such: ( velocity X 60 ) divided by 1.166666666666 = rpm's rpm's at a velocity of 3000 would be 154,285 rpm's..........or there a bouts. Do we know the exact speed of the pre-M193 ammo? |
|
Quoted:
Do we know the exact speed of the pre-M193 ammo? Quoted:
Quoted: Might be............I dunno. That's why I stated @3200 fps.
Maybe I should have stated it as such: ( velocity X 60 ) divided by 1.166666666666 = rpm's rpm's at a velocity of 3000 would be 154,285 rpm's..........or there a bouts. Do we know the exact speed of the pre-M193 ammo? I don't. It might be in the book "Black Rifle". There is a fairly extensive discussion of early ammo in that book. |
|
Quoted:
I did a quick Google search and a couple sites state that the Marines adopted the A2 in '83 and the Army in '86. My cousin was qualifying at Parris Island with an A2 in summer of 85. Fort McClellan had just gotten A2s for the MP training companies in the summer of 92. The Chemical training companies still had A1s. |
AR Sponsor