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GM-M27 16" 300 BLACKOUT


Product Description

300 BLACKOUT, 1:7 Twist, 16" long, 4150 steel, weighs 1.75 lbs., carbine length, button rifled, air gauged, stress relieved, chrome line bore and chamber, phosphate finish, 7 flute, 5/8x24 muzzle threads.

Barrel not pinned for front sight base.

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Product Reviews

Previous | Showing reviews 6-10 of 42 | Next

  1. great barrel great price not great price for shipping 5 Star Review

    Posted by on 22nd Apr 2019

    I love GM barrels. There excellent quality and a great value. I just wish they wouldn't charge so much for shipping.

  2. I couldn’t ask for better 5 Star Review

    Posted by on 27th Dec 2018

    I have purchased barrels from Green Mountain before and know their quality to be top notch so I felt confident that this new .300 Blackout barrel would be no different. I shot it once at 25 yards to make sure it was on paper then moved it out to 100 yards. First shot was a bit high, second shot was a bit low, and the final shot was money. I couldn’t ask for a better barrel.

  3. Birthing problems at first, but the baby is healthy now 4 Star Review

    Posted by on 22nd Sep 2018

    Using the bullets I prefer for hog and deer hunting (Barnes 110gr black tips), it would consistently put the 1st shot 1.5" low at 50yd (1" low at 34yd and 3" low at 100yd). Tried different magazines, number of rounds in the mag, 1st round loaded to the left in the mag, 1st round loaded to the right in the mag, bolts, methods of letting the BCG go forward to chamber the round, different suppressors, no suppressor, taking the upper apart and putting it back together, examining the feed ramps, different powder charges, different buffer weights, different buffer springs, different lowers, checking all bolts and bbl nut for looseness, breaking it in by firing about 200rds...Nothing made a difference, the first shot fed from any mag would be consistently low...not good for hunting. I even fired a group consisting of only first rounds chambered...tight group, just all shots low. Oh, the other 4-5 shots in the groups would give a tight group, just higher than the 1st shot chambered. Fired it fast to heat the bbl; fired it super slow 1 shot every 5 minutes with 2 fans blowing on the bbl to keep it ambient temp, and still the 1st shot was low. Even measured the bbl throat...it was fine and read as a new barrel. Only thing not tried was another upper receiver.

    Tried some Nosler 125gr Ballistic Tip bullets (my 2nd choice for hunting), and it was like flipping a light switch...1st round always in the group and no longer low. Go back to Barnes and again low. Go back to Noslers and 1st round back inside the group. I know this seems to make no sense, but I've got the targets and witnesses to prove it.

    It's now sighted in with the Noslers and is a 1 MOA or less barrel with them. Last 3 shots fired at 100yd off a rest to verify my hunting sight setting were 3/4" center to center. If it'd liked the Barnes, I'd of given it 5 stars.

    Once broken in, very little copper fouling, easily removed with plain Hoppes #9 by letting it soak about 15 minutes. Nice looking chrome lining. Concentric muzzle threads to the bore. Likes my Ark30 suppressor; not as accurate with the Quicksand suppressor, but then most bbls like the Ark30 better. Shoots a little more accurate with the Ark30 than with no suppressor. No failures due to not enough gas. Worked with standard buffer, H, and H2 buffers. I only shot supersonic ammo.

    I test Blackout bbls for throat wear as a hobby, measuring it with throat erosion gages. I didn't have a 4150 button rifled chrome lined in my dozen or so bbls, so that is what attracted me to this bbl. My other 4150 chrome lined bbls are CHF and "double" chrome lined, so I'll have this bbl to compare with them.

  4. Operates flawless and 1 moa accurate! 5 Star Review

    Posted by on 21st Apr 2018

    Great barrel and even better at its price point. A lot of people out there advertising great barrels. Green Mountain has not disappointed me with this one. Spot on in quality and accuracy. Loaded up 220gr and 150gr and both cycled great. Next week we will see what she does with 125gr pushing 2150 to 2200 fps.

  5. As always, very happy 5 Star Review

    Posted by on 26th Sep 2017

    Great barrel. Well made. Do miss the gas block pin hole for anchoring the has block. Now that I know which lo-pro gas block to use. I did pin my other 300 bk barrel.

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