Gas Port Data

**vicious_cb** · 04-14-18, 23:16

Finally got confirmation from a Geissele employee that the USASOC URG-I 14.5 midlengths will be using 0.076" gas ports. There you have it, thats about as close to a "mil-spec" gas port size for a midlength as you're going to get. I guess companies like BCM who have been using that size for years had it right all along.

**everready73** · 04-15-18, 09:38

Good to hear. I definitely prefer that size for midlength 14.5/16 inch barrels. Hopefully just the barrels will be available at some point. I know DD is making these, but the ports on their brand barrels seem to be closer to the .080 range

**WS6** · 04-15-18, 09:41

Originally Posted by vicious_cb

Finally got confirmation from a Geissele employee that the USASOC URG-I 14.5 midlengths will be using 0.076" gas ports. There you have it, thats about as close to a "mil-spec" gas port size for a midlength as you're going to get. I guess companies like BCM who have been using that size for years had it right all along.

It depends on bore diameter, as well. For example, one of my 14.5" middy's I've owned measures 0.0735" and runs VERY well, can or not. It all depends on pressures, and bore dimensions affect this greatly. All the G-upper is, is a DD barrel with the G rail. It's going to have DD specs, and 0.076" is their spec for a 0.750 gas block journal 14.5" middy. No magic, here.

**Hulkstr8** · 04-15-18, 11:30

Originally Posted by Iraqgunz

Very hot for a mid. I assume when you say carbine buffer, you mean the standard 2.9 oz and not an H buffer. I have probably said this a thousand times or so, but carbine buffers belong in the trash. I have yet to see one properly made carbine or mid upper that will not function with an H buffer.

You feel the same in regards to the 300 BLK? I'm fairly certain the cartridge was designed to be used w/ the carbine.

**Hulkstr8** · 04-15-18, 11:35

Also, my Green Mountain Rifle 11.5" is spec'd at 0.080 - I bought it before I knew better.

**Defaultmp3** · 08-06-18, 00:50

Bump for exposure.

**Bob Sacamano** · 08-06-18, 06:18

Good info in this thread. Thank you for organizing it and thank you to those that have helped populate it. I reference it frequently.

A set of pin gauges are cheap.

https://www.amazon.com/HFS-0-061-0-2...70_&dpSrc=srch

**lysander** · 08-06-18, 11:58

Originally Posted by P2000

Numbered drill bits ok enough, but I'm worried about regular drill bits, one not fitting, the other loose, and the "measurer" splitting the difference. This is the internet we are talking about.

Sent from my XT1565 using Tapatalk

Generally speaking, gas ports are drilled with standard drill bit sizes, so the last one that fits, is more than likely the drill bit size that made that hole.

Oh, by the way, drill bit (in the gas port range) make holes with a tolerance, up to +.004", if you want any better than that you have to ream them then you can get +.001.