Gas Port Question

[Shivesy]

I have a 20" Grendel barrel with a rifle length gas system and my gas port hole size is .093 (3/32"). This barrel cycles very well.
Now I an ordering 3-16" bull barrels with carbine gas systems. Would the gas port hole size be larger or smaller than my 20" barrel?

[Bill Alexander]

16" barrels do not balance well with carbine gas systems. The mid works best with a port of 0.078". Will work down to 0.073" but becomes very fussy in a production gun. Carbine systems are very difficult until barrels are down to 14.5"

[bobke]

Bill-
I have a rifle length gas system on 20" Bartlein barrel also, but gas port hole size is .81-.82, with fixed gas block. Have occasional ftf's with less than full loads, using H2 buffer and standard carbine spring with UBR stock. Any guidance to share in this regard? Have a PRS that I could put on, but am holding off, pending continuing testing. Have thought from get go I was a bit undergassed, but don't want to mod the gas port hole size against better judgment. Thanks for dropping in here often-I know there's an appreciative crew employing your shared wisdom.

[tcte]

If you dont mind me asking Shivesy, where are you ordering the 16" bull barrels from?thanks

[Bill Alexander]

Bill-
I have a rifle length gas system on 20" Bartlein barrel also, but gas port hole size is .81-.82, with fixed gas block. Have occasional ftf's with less than full loads, using H2 buffer and standard carbine spring with UBR stock. Any guidance to share in this regard? Have a PRS that I could put on, but am holding off, pending continuing testing. Have thought from get go I was a bit undergassed, but don't want to mod the gas port hole size against better judgment. Thanks for dropping in here often-I know there's an appreciative crew employing your shared wisdom.

That port size will be very soft and as you have found will not always function with all ammo. The Hornady loadings may not always function and lighter bullets can also be a problem. Factory barrels 20" long use a standard rifle length gas system and are ported 0.094" This is still temperamental but is a good compromise for all factory loads and most hand loads.

It is my opinion that the 20" Grendel barrel with a rifle gas system is one of the optimum set ups. The gas system is mild without being unreliable but still allows the addition of a silencer without overwhelming the cycle. I think that the 14.5" barrel with a carbine gas system is the next best set up.

[bobke]

123 Amax with 31.5 CFE functions near 100%. 107 Sierra with 30.0 TAC is good, but 29.0 8208 missed occassionally with 107 Sierra and 108 Lapua, but manually feeding yielded good accuracy. Seems I need to cut back to T2 buffer which is about .4 oz less than H2 that I have, stiil using a std length carbine spring. Fortunately, the 123 Amax/31.5 CFE shoots well, but I've been trying to get 107/108's to function properly, and only seems so at near 100% loadings. Is this a good case for bumping up the gas port hole size or is there a lower hanging option that might function more reliably? Thx for feedback.

[Drifter]

I have a 20" Grendel barrel with a rifle length gas system and my gas port hole size is .093 (3/32"). This barrel cycles very well.
Now I an ordering 3-16" bull barrels with carbine gas systems. Would the gas port hole size be larger or smaller than my 20" barrel?

I have a 16" M4-contour Grendel barrel with carbine gas system that was originally undergassed. Reamed the gas port hole using a 1/16" drill bit (0.0625"), and it runs fine now.

[Shivesy]

If you dont mind me asking Shivesy, where are you ordering the 16" bull barrels from?thanks

I thought I would give Dan a call over at McGowen barrels. He got me set up with a 20" 6.5 BPC on my first and only barrel. I have been real happy with that set-up and factory Hornady ammo.

[Bwild97]

What is a 6.5 BPC? new Grendel variant?

[Lead Chucker]

Great info! Thanks Mr. Alexander for the help. I have a 18" with midgas system, & putting together a 16" with midgas system also. I never measured the gas port on my 18" before putting it together, but I havnt had any problems with it. I havnt measured the gas port on the 16" yet, but it should be .078 give or take .001 right?

Thanks again

[Lead Chucker]

I measured the gas port on the 16" barrel with mid length gas system on it. It measured .092, it may be alittle over gased.