Warning

 

Close

Confirm Action

Are you sure you wish to do this?

Confirm Cancel
PSA
Member Login

Posted: 9/18/2009 4:54:06 AM EST
[Last Edit: 9/18/2009 7:41:57 AM EST by cmeyer001]
Based on experience does there seem to be an ideally dimension for gas port diameter on a 12.5" barrel?

This is asked from the perspective of cutting down a 14.5" MRP barrel to 12.5"

From other posts I have gleaned gas-port "spec" to be:
10.5" .093"
11.5" .081"
14" .063"
16" .063"

Inference says an ideal gas port size for 12.5 may be somewhere around .070" or so?

Thanks for any inputl
Link Posted: 9/18/2009 7:32:51 AM EST
I just finished cutting a 20' Bushmaster bbl. down to 11.5

I started at 0.59 and ended up at 0.70. The bolt would activate the mag catch with military m193 @ 66.5

@ 0.70, federal 223E had enough umph to lock the bolt on an empty mag

Link Posted: 9/18/2009 7:50:21 AM EST
[Last Edit: 9/18/2009 7:51:26 AM EST by gmtmaster]
Originally Posted By hemcon9:
I just finished cutting a 20' Bushmaster bbl. down to 11.5

I started at 0.59 and ended up at 0.70. The bolt would activate the mag catch with military m193 @ 66.5

@ 0.70, federal 223E had enough umph to lock the bolt on an empty mag



What happens when you have to shoot substandard ammo? Rifle fails?

"Ill never run steel cased ammo" may not hold water when SHTF.
Link Posted: 9/18/2009 12:22:40 PM EST
I'm just giving him some input.

The gun is working well with the lightest ammo I have in the shop. Besides, I live in America where ts NEVER hits the f.
Link Posted: 9/18/2009 3:40:04 PM EST
[Last Edit: 9/18/2009 3:40:56 PM EST by Shung]
I built my 10.3 barrel..

I started at 0.070 but with a full bolt carrier it was not enough to lock the bolt back on an emply mag... I finished using 0.082" and it works fine, with a Mc farland gas ring, and using good quality ammo..

I kept a sporter cut bolt carrier to use with crap ammo..
Link Posted: 9/18/2009 3:49:32 PM EST
Link Posted: 9/19/2009 4:23:59 AM EST
Based on input looks like a .080 gas port and then variable buffers (H or H2) should produce a
weapon reliable on various types of ammunition.

Thanks for the input.
Top Top