NWcityguy2
Member
With the general lack of information about this barrel (and its attractive price) I thought it would be helpful to post a review with pictures. Green Mountain is more known for their awesome 10/22 barrels and their not so awesome AK-47 barrels, at least from what I have read.
This is a Green Mountain 20" Government Profile barrel. http://www.gmriflebarrel.com/back-in-stock-m16a2-5-56mm-20-barrel-with-extension-1-8-twist/ I bought it to replace my Del-ton 16" dissipator barrel, which was a good barrel. The problem was it shot my favorite budget bullet, the Hornady 55gr SP w/ cannelure worse that cheap FMJ bullets. Literally 4 moa on a good day. The Del-ton did shoot Nosler 53gr BTHPs 1 moa, the price of those can add up quick. Given that I have an almost full 50 cal ammo can of the Hornady bullet, it made financial sense to give another barrel a try.
I bought this barrel on Feb. 24th for $159.95 and $15.18 shipping for a total of $175.13. It shipped on the 28th and I received it on March 4th. It was well packaged inside kraft paper, bubble wrap and a taped shut cardboard box.
Key features
- Made from 41V50 steel
- 5.56 chamber (advertised as such, I have no chamber gauges to measure it with)
- 1/8 twist
- Chrome lined chamber and barrel
- M4 feed ramps (which are more and less standard these days, but there are still A1/A2/A3 uppers floating around that are meant for rifle feed ramps)
- Parkerized outside
- 1/2"-28 threads muzzle
- Rifle length gas system
- Gas port measures .093"
- .750 Gas block size
- The barrel is not dimpled for gas block set screws (not everyone will agree on how important this is, but it certainly doesn't hurt. I ended up buying a clamp on gas block)
- Comes only with the barrel extension
- Not drilled for a FSB, which aren't as common on 16" barrels, but still fairly common on A2 type rifles)
Gas port and thread protector. "5.56 Nato 1/8" are the only markings on the barrel.
Cleanly cut threads.
After it was installed on my AR. It's a very simplistic build. Right now it has a 1x20mm Weaver Kaspa scope on it but all accuracy testing was done with my 2.5-10x50mm Nikon Monarch scope.
Initial Accuracy Tests
The one thing I was to stress is that I didn't tune any load specifically for this rifle. I simply shot what I had on hand. Both of my handloads were using 25 grains of Accurate 4064 powder. There is a high probability that I can find more accurate loads using different kinds and amounts of powder. There is also a high probability that a better shooter could shoot tighter groups then I did. I mainly shoot handguns (USPSA/IDPA) and built this as a 3-gun rifle. I shoot very little from a bench. All groups were fired from 100 yards.
The best performing was the Nosler 52gr BTHP, which shouldn't be a surprise.
A close second was the Hornady 55gr SP w/ Cannelure. This is a 6 round group because I lost count while shooting. Since this group is more accurate than is needed for any 3-gun competition I shoot, they make strong case for selling my 800 remaining Nosler bullets.
Finally I shot some factory loaded Winchester .223 64gr Power-Points, which are a passable self-defense round. These are what my agency issues as duty (and practice) ammo so I have a couple boxes laying around. Certainly a drop in performance.
I hope everyone enjoyed my initial impressions and review of the Green Mountain 20" 1/8 AR barrel. Since I shoot about 3000 rounds a year and at a responsible pace (IE no mag dumps) it would take years for me to see any lifespan difference between this barrel and a non-lined 4140 barrel. Perhaps I'll update this thread as time goes by with round counts. My personal opinion though is that it is hard to wear out any AR barrel if you are shooting bullets like each one counts.
This is a Green Mountain 20" Government Profile barrel. http://www.gmriflebarrel.com/back-in-stock-m16a2-5-56mm-20-barrel-with-extension-1-8-twist/ I bought it to replace my Del-ton 16" dissipator barrel, which was a good barrel. The problem was it shot my favorite budget bullet, the Hornady 55gr SP w/ cannelure worse that cheap FMJ bullets. Literally 4 moa on a good day. The Del-ton did shoot Nosler 53gr BTHPs 1 moa, the price of those can add up quick. Given that I have an almost full 50 cal ammo can of the Hornady bullet, it made financial sense to give another barrel a try.
I bought this barrel on Feb. 24th for $159.95 and $15.18 shipping for a total of $175.13. It shipped on the 28th and I received it on March 4th. It was well packaged inside kraft paper, bubble wrap and a taped shut cardboard box.
Key features
- Made from 41V50 steel
- 5.56 chamber (advertised as such, I have no chamber gauges to measure it with)
- 1/8 twist
- Chrome lined chamber and barrel
- M4 feed ramps (which are more and less standard these days, but there are still A1/A2/A3 uppers floating around that are meant for rifle feed ramps)
- Parkerized outside
- 1/2"-28 threads muzzle
- Rifle length gas system
- Gas port measures .093"
- .750 Gas block size
- The barrel is not dimpled for gas block set screws (not everyone will agree on how important this is, but it certainly doesn't hurt. I ended up buying a clamp on gas block)
- Comes only with the barrel extension
- Not drilled for a FSB, which aren't as common on 16" barrels, but still fairly common on A2 type rifles)
Gas port and thread protector. "5.56 Nato 1/8" are the only markings on the barrel.
Cleanly cut threads.
After it was installed on my AR. It's a very simplistic build. Right now it has a 1x20mm Weaver Kaspa scope on it but all accuracy testing was done with my 2.5-10x50mm Nikon Monarch scope.
Initial Accuracy Tests
The one thing I was to stress is that I didn't tune any load specifically for this rifle. I simply shot what I had on hand. Both of my handloads were using 25 grains of Accurate 4064 powder. There is a high probability that I can find more accurate loads using different kinds and amounts of powder. There is also a high probability that a better shooter could shoot tighter groups then I did. I mainly shoot handguns (USPSA/IDPA) and built this as a 3-gun rifle. I shoot very little from a bench. All groups were fired from 100 yards.
The best performing was the Nosler 52gr BTHP, which shouldn't be a surprise.
A close second was the Hornady 55gr SP w/ Cannelure. This is a 6 round group because I lost count while shooting. Since this group is more accurate than is needed for any 3-gun competition I shoot, they make strong case for selling my 800 remaining Nosler bullets.
Finally I shot some factory loaded Winchester .223 64gr Power-Points, which are a passable self-defense round. These are what my agency issues as duty (and practice) ammo so I have a couple boxes laying around. Certainly a drop in performance.
I hope everyone enjoyed my initial impressions and review of the Green Mountain 20" 1/8 AR barrel. Since I shoot about 3000 rounds a year and at a responsible pace (IE no mag dumps) it would take years for me to see any lifespan difference between this barrel and a non-lined 4140 barrel. Perhaps I'll update this thread as time goes by with round counts. My personal opinion though is that it is hard to wear out any AR barrel if you are shooting bullets like each one counts.
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