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Posted: 9/17/2026 12:32:40 AM EDT
[Last Edit: bud7h7][Edited]
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I might want to cut a 14.7 to 11.5, could the existing gas port size be an issue? It's a BCM (don't know the super secret port size) carbine gas system, and it would be run suppressed. |
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So it appears it now has a mid-length gas port. And the BCM 11.5 is carbine. So the gas tube is different as well. Faxon makes a 11.5 with mid-length gas. I had one, but used an AGB. Maybe someone else will chime in that has done this. But eventually this gets to be a lot of work over just getting another barrel. |
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You should be fine especially suppressed. Gas ports are larger as they get longer so going shorter isnt an issue on most barrels given you are using normal gas system lengths with appropriate dwell time. 14.5 BCM is .076 according to this google doc so .076 on an 11.5 is just fine. If you have a midlength, and you are going to an 11.5 midlength, that is severely reducing the dwell time and IMO an 11.5 midlength is kinda stupid unless its 100% suppressor. You need quite a large gas port for that to run unsuppressed probably .080 or so reliably but may get away with .076 as it is. Wont know till you test. Shortest I would go on a midlength to ever run unsuppressed is 12.5" and with a .073 gas port that will get you down to a std carbine spring and std or H buffer to cycle .223 reliably. Have a 12.5" midlength right now with a huge .083-ish noveske gas port but then a YHM suppressor gas block drilled to .076 (probably .073 or so effective size) and it cycles without a can .223 just fine with a carbine spring and H buffer. had a previous build with a 12.5" ballistic advantage midlength that had a BRT .076 gas tube (also .073 at the end of the day) and it performed the same. |
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Appreciate the replies. It's a carbine GS, I failed to include that. Spoke to my BIL and he has cut two (14.7 to 11.5) that ran fine from day one, and a 10.3 that needed a little more tuning. None have AGB. Even so I'm just getting a new 11.5 and keeping the 14.7 for another project. |
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