First time I have seen US riflemen practice full-auto fire.

FWIW, it looks like they were using Mk318 Mod1 ammo.

YouTube

RANGE DAY with U.S. Marines at Camp Lejeune (FULL AUTO)

Elements of the 26th MEU, Battalion Landing Team 1/6, conduct a range part of Military Operations in Urban Terrain (MOUT) training on Marine Corps Base Camp ...

Something, something, piston reduces gas blowback when using a suppressor.

Farmplinker said:

Something, something, piston reduces gas blowback when using a suppressor.

Hum, at least some suppressors are reducing gas blowback, but it seems that the model selected by the USMC doesn't...

EmericD said:

but it seems that the model selected by the USMC doesn't...

USMC uses vintage Knight's suppressors that are about 20 years old, if not older.

I think they just wanted to get rid of the ammo in full auto instead of practice it in form of combat. Semi auto is the way to go in combat 

Great find.  Thanks for posting!

The full video has target results:

YouTube

Full Auto COD Guns in Real Life #callofduty

Exploring full auto recoil patterns in real life. How does it compare to certain video games?How full auto ownership is legal: https://youtu.be/li5T1hFHE_oW...

By the way any ideas on why one would try a long stroke piston in AR15?

Looks like a rather stright forward mod , bolt carrier key was replaced with a bolt in piston .

YouTube

Slow Motion PWS Long-Stroke Piston System

http://primaryweapons.comhttp://facebook.com/primaryweaponshttp://instagram.com/primaryweaponsHigh speed videography of a functional cutaway of the PWS long-...

Mr. T (MrT4) said:

By the way any ideas on why one would try a long stroke piston in AR15?

It has been done decades ago with the Daewoo K2 rifle

Because some people still think it's 1966, and M4s have the same problems as early M16s. Also, muh Kalashnikov.