I have a 6.5 build that isn't getting enough gas and I'm looking at the gas port as the culprit.  It's a 22" barrel with what appears to be a .068" gas port for a rifle length gas system.  This is actually smaller than the port on a midlength 5.56 barrel I had to compare.  

Anyone know if this seems way too small for a 6.5 Creedmoor?

I ask because the rifle is short stroking no matter how much i open the adjustable gas block.  I installed the gas block using the SLR jig so I'm pretty sure its aligned properly.

Rob

Have you tried lowering the buffer weight?

Somebody switched some numbers around.

If using RLGS with .260 Rem or 6.5 Creedmoor, .086" is one of the main port sizes used by competent manufacturers, shops.

I recall George Gardner mentioning this port size once.  It's smaller than a .308 or 5.56 .0937" port, since the port pressure is much higher with most 6.5-08 loads, especially the 140s.

I'm not aware of any cartridge in the AR15 that uses a .068" port on a RLGS.  That's CLGS port size for some of the 5.56 combinations.

What I would try is opening it to at least .078" with a 5/64ths bit, if not a .086", ensuring not to blow through to the rifling on the opposite side, or have a competent smith do this if you can find one.  Use cutting fluid, and knock out the burr inside the bore with a brass brush afterwards.

You'll probably end up with a .086" though.

I'm running a standard .308 buffer weight.  Not sure if its advisable to run something lighter.

Thanks for the info.  I was pretty sure the port was a good bit undersized. I'll probably send it back to the manufacturer and see if they will fix it.  When i talked to them they seemed to brush off my concern that the port was undersized but we'll see what happens I guess.

Rob

I have been to the 6.5 Creedmoor gas port rodeo. .068 is way to small.  Numeric drills are cheap and its an easy fix to do it yourself if you have any skill at all.  I clamp the barrel in a vice with the gas port facing you. Stick an old cleaning rod down the bore so the bit doesn't crash into the opposite side. Buy a #46 (.081)#44(.086) short High speed drill bit(Brownells sells them). I use a high speed air drill. Lube your bit with cutting oil and drill it out to the next bigger size. The bit will follow the existing hole if you have it reasonably straight when you start. I blow out the gas port with compressed air and patch the bore to remove any metal chips.  Put your gas block back on and go test fire it one round. If the bolt doesn't lock open on an empty magazine, repeat the procedure with the next size drill. If you have an adjustable gas block just drill it with a #42(.093) and adjust your gas block till it locks open on an empty mag. I don't like adjustable gas blocks and prefer to open up the gas port to the minimum that will cycle the action reliably.

The cleaning rod tip is a good one.  I may just solve the problem myself.

Thanks,

Rob

I normally mount them in my drill press and set the stop so I can't go deep enough to hit the rifling on the far side.

Generally speaking you want more mass to "tame" excessive gas pressure (oversized gas port), but if the gas port is undersized, you should be able to lower buffer weight to achieve reliable cycling.

Many low mass setups with the lightest weight buffer and BCG with reduced gas flow (either via smaller gas port or adjustable gas block) function very well. The "drawback/s" to the lower total reciprocating mass is a higher cyclic rate (noticeable difference in recoil impulse) and the necessity to keep the system lubricated. Dirty/carbon fouled usually isn't a problem as long as you use enough lubrication. If you skimp on the lube, that's when you'll start to run into issues (in my experience).

Email sent.

Good Info! I just got my DPMS Heavy Fluted barrel back from a company that was supposed to enlarge the hole and thread the muzzle. They did thread it but the hole is the same size it was. When I called I was told that they really dont know what size a 6.5 should be so the guys in the shop may have decided not to change it. Very fast service but not sure they did not overlook the primary request which was to open the port. I even told them what ammo I was using and all the details about the gun in the work order sent with the barrel. Guess I will do it myself this weekend if I can find the bits. This is a DPMS barrel and they are disavowing any support of it.

Try a jp scs with the weakest spring.

Who makes the barrel?

I've got to hand it to you.  This post is one of the most helpful I have ever seen or needed.  I too recently built an AR-10 pattern 6.5 Creedmoor rifle with short stroking due to lack of adequate gas volume to cycle the action.
I used an Aero Precision upper and lower, topped off with a Proof Research 20 inch carbon wrapped barrel, and Superlative Arms adjustable gas block.  In an attempt to manage the high pressures of the 6.5 Creedmoor, Proof uses a +2 ELGS trade named "CAMGAS".  The gun would short stroke and not cycle with the gas block fully open with no bleed-off.  I took your advice and drilled the gas port out to .089" with the #43 numerical drill. Immediately afterwards, the gun cycled flawlessly, with bolt lock after the last round fired, and groups tightened up significantly.  I reached out to Proof and they indicated that new production 6.5 Creedmoor barrels are shipped  with an enlarged 0.086" gas port.  It seems our understanding of the functional characteristics of this impressive round in the AR platform is just beginning.  Thank you so much for the valuable information you provided in this post.  And yes, I did use a cleaning rod in the bore when drilling to prevent pass through of the drill bit to the opposite inside of the bore.