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M16 barrel twist change

Posted: Fri Feb 26, 2016 10:23 pm
by darwin
I recently read something about the M16 and how the Army resisted changing to it. A couple of changes they made were the barrel twist and the gunpowder used. I also seem to remember that they did away with chrome lining in the barrels.

Does anyone know what the change in barrel twist was and what effect it had on the performance?

Thanks.

Posted: Fri Feb 26, 2016 11:52 pm
by Sparky45
http://weaponsman.com/?p=7291

This gives some info.

Posted: Sat Feb 27, 2016 9:16 am
by rowe_s
Sparky45 wrote:http://weaponsman.com/?p=7291

This gives some info.

good info.

Posted: Sat Feb 27, 2016 3:41 pm
by darwin
From the chart, it looks like 1:7 works best over the entire range of bullet weights.

Clicking through, I found a good article about .223 vs 5.56

http://www.luckygunner.com/labs/5-56-vs-223/

Posted: Sun Feb 28, 2016 10:04 am
by erle
All I know about it is that I acquired a new Colt AR-15 2 years ago. The twist is 1:7 & the barrel is NOT chrome lined.

Erle

Posted: Mon Feb 29, 2016 7:55 pm
by darwin
erle wrote:All I know about it is that I acquired a new Colt AR-15 2 years ago. The twist is 1:7 & the barrel is NOT chrome lined.

Erle


I was asking about the M16. They did not perform well at all in Viet Nam and the barrel and powder used were blamed for the malfunctions. Some believe that the Army purposely sabotaged it because they did not want it. They originally turned it down, the Navy adopted it. The Army did so later, but forced the changes.

Posted: Wed Mar 09, 2016 3:04 am
by El Hombre
darwin wrote:
erle wrote:All I know about it is that I acquired a new Colt AR-15 2 years ago. The twist is 1:7 & the barrel is NOT chrome lined.

Erle


I was asking about the M16. They did not perform well at all in Viet Nam and the barrel and powder used were blamed for the malfunctions. Some believe that the Army purposely sabotaged it because they did not want it. They originally turned it down, the Navy adopted it. The Army did so later, but forced the changes.


They didn't issue cleaning kits the first couple of years; but then they learned and got those out to the troops. About '67 or so. Did the chrome plated chamber and barrel about the same time. The powder had calcium carbonate in it; same stuff as Tums anti-acid. They were reclaiming cannon powder from WW2, the process used acid and to neutralize the acid, they put 20 pounds of Tums per ton of powder. The tums would deposit on the walls of the gas tube and eventually close it off. Found out 5 pounds of tums would do the job and not foul the gas tube. That's why you see WC844 and WC846 powder, the latter had fewer tums in it. It's a pretty good rifle and ammo these days. But the current bullets don't seem to stop whom they're shot at. Saw a post that Hornady 75grain bullets do a real job on anyone they hit.

Posted: Sun May 15, 2016 9:49 pm
by Hawkmoon
1:7 is a bit fast for the old standard, 55-grain bullet, but nobody seems to want those any more (except us olde phartes on a budget, who figure if it was good enough to carry in Vietnam it's good enough to punch holes in paper). IIRC, standard issue today is the 62-grain, and the "operators" get heavier still.

1:9 seemed to be the accepted "universal" twist for many years, but with the move to shooting 75-grain and heavier bullets and using the AR-15 as a platform for high power and benchrest competitions, I guess 1:7 is taking over.