The GM-M49 is an 18” long 223 WYLDE chambered AR15 barrel with a button rifled, stress relieved .2195” bore and .224” groove diameter and 1:8” twist.
Features include a Rifle Length, .750” diameter gas system, a Nitride finish on 416 stainless steel, assembled extension with M4 feed ramps and ½-28 muzzle threads. 2.5 lbs.
Posted by Robert on 23rd Jan 2017
I am a type 7 mfg and there is only one grip I can see with this barrel. The barrel info is marked right in front of the barrel extension, so once the upper is built you can't see it. For most it will only be a cosmetic issue.
As far a performance goes they seem awesome. I was quite surprised when they were stacking 55gr American Eagle ammo @ 50 yards during function testing. It will be nice to see what they will do once broken it and fed some good ammo.
Posted by Bones on 9th Dec 2016
I replaced my gm 20 inch fluted which is a great barrel with this 18 in .The heavier profile of this one took the heat of repeated firing better than my 20, loss of velocity was on 24 fps with my 77 grain berger load, clocked at 2766 fps accuracy was 1.1 in at 100, should get tighter once it is broken in. I will give an update on barrel in a couple weeks. as always green mountain makes a great barrel at a better price.