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Built a 6.5G BA 12.5 upper with the usual components, Vltor Mur 1A Upper, GB Bolt, Vltor GB(non-adjustable), WMD carrier, and Chandler handguard...
Short stoking with full power loads over 2 trips to the range... Pulled the GB and the port was .055" using a drill bit... Drilled it out (my first time) to .073", and everything is running great...
It's accurate and I'm happy, but has anyone else seen a small gas port on 12.5" BA barrels?
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My 12.5 will be here next week. WIll measure and inform. Thanks for the tip.
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.055" would work with some cans that generate a lot of accumulation, but sounds a bit small for CLGS Grendel, even with 12.5".
It would work better on a 5.56 NATO since bore space is less, but Grendel allows a lot of venting/pressure release for the bore space.
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Schrambo Wrote:Built a 6.5G BA 12.5 upper with the usual components, Vltor Mur 1A Upper, GB Bolt, Vltor GB(non-adjustable), WMD carrier, and Chandler handguard...
Short stoking with full power loads over 2 trips to the range... Pulled the GB and the port was .055" using a drill bit... Drilled it out (my first time) to .073", and everything is running great...
It's accurate and I'm happy, but has anyone else seen a small gas port on 12.5" BA barrels?
I just my 12.5" BA barrel in and the gas port measures 0.063. What size drill bit did you use to drill yours out? Where did you gets yours from? Did you just a cordless drill, wood dowel rod, and some oil?
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You need a #49 bit. Drill press, V block, and a depth stopper. If you have none of the above, find a gunsmith.
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This was asked in the BA industry forum on ar15.com. BA stated that they purposely did this as they believe people would be shooting this barrel length suppressed and said a carbine buffer was recommended.
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12-09-2017, 02:28 PM
(This post was last modified: 03-14-2018, 03:21 AM by Schrambo.)
irishpride114 Wrote:I just my 12.5" BA barrel in and the gas port measures 0.063. What size drill bit did you use to drill yours out? Where did you gets yours from? Did you just a cordless drill, wood dowel rod, and some oil?
Barrel clamp, .073 bit, drill press set short, wood dowel rod just in case, and oil... Added an adjustable gas block to tune it for my suppressor... Carbine buffer and spring works great now...
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I have a new, recently purchased BA 12.5" Gr barrel. I've put a few rounds thru it, it's ejecting empties OK, but not loading a new round. All indications are that its under-gassed. Yesterday I called the BA tech line, and was told that my barrel port should be .0595". Today I pulled the gas block and gas tube off, the barrel port is .0550" using calipers, I don't have drill bits to get any more accurate than that.
I'm using the BA gas block and gas tube which has a roll pin hole that lines up with the slot/notch in the barrel and two set screws. The residue stain on the barrel indicates that the barrel port was centered in the gas block port.
Sounds like I need to open up my barrel gas port.
Edit; I'm running standard carbine buffer and spring.
