Budget 11.5 build.

[xtremesvc]

OK...Im on a very tight budget, so I started off with an old Eagle E2 16" A2 upper I had stucked away a long time ago. My smith cut the barrel down to 11.5 and I put it on my Spikes lower with RRA 2 stage trigger. Did nothing to the gas port as of now and went out to the range to see what it would do with different ammo I had in my inventory. Also had a standard buffer and a spikes T2 buffer to try.

1st..Remington 50 bulk...wouldnt lock back and brass was munched.
2nd.Winchester 20rd box.......same as above.
3rd.American Eagle 20rd box..same as above. (Federal brand ammo)
4th.Malasian NATO..............same as above. (not hot at all).
5th.Remington 20 rd box....bolt locked back but didnt eject case.

Swapped buffers with the same results.
I was shocked with the difference in the Remington ammo! You could feel and hear it between the 50 rd and the 20 rd box and this stuff is suppose to be the same but packed different.

The stock gasport measuered at .0680.

Now, my question is should I open up the gasport to a #46 bit
(.0810) or??

[Col_Crocs]

.068 may be too small for an 11.5 but .081 is definitely far too large. IIRC, Robb Jensen mentioned some time ago that an 11.5's max port size should only be .071. Give me a bit to dig up that thread.
First things first though, prior to testing the upper, did you or your smith do a once over to see if everything on the upper was gtg, the fsb and gas tube in particular? Did you Use a new BCG? If not, did you go over it and checked if everything was gtg? Ie. Carrier key, gas rings? Just trying to eliminate factors before you go and have it opened up.

ETA: found it. https://www.m4carbine.net/showthread.php?t=58991
Sorry for misquoting Robb. His post states his preferred/recommended max port size and not an actual max port size for said barrel length.

[xtremesvc]

This upper was running good before cutting barrel. Used it in a couple NRA carbine courses before being put away 10 years ago. I do need to restake the keys, but this was normal for the Eagle uppers. I bought it before the ban took place as an complete rifle and the lower is being used with a cmmg .22 upper for the kids.

[Col_Crocs]

This upper was running good before cutting barrel.

Ya but now that it's cut, it would be wise to go over everything just to eliminate variables before enlarging the gas port. The reason for which is so your port remains the only factor in the equation, thus, ensuring you only enlarge it to what is really needed and not too far so as to compensate for any leaks in the system. It's not a guarantee that you'll find any or even that any minor leaks would be enough to really affect the system but it's a DIY insurance check that will take all of 5mins. Keep us posted.

[xtremesvc]

Just picked up # 50, 49, 48, 47, 46 wire bits this morning to open up the gas port. Went over the rifle last night and GTG on all the internals.
I'm also going to get a o-ring to place on the extracter to help and will post picks this afternoon.

FYI...this is on an stamped legal lower that was done last December.

[SWATcop556]

Forget the O ring for your extractor. Just make sure you have the 5 coil spring.

[xtremesvc]

Took the #50 (.070) bit and cleaned up the port (went in by hand)and then used the #49 (.0730) to open the port. Gas port mics out at .072 and now back to the range.

[xtremesvc]

Went to the range this morning...

Installed o-ring on extractor and the bolt locked back 4 out of 20+ rds. All brass landed at the 3 o'clock when the o-ring was used. When the o-ring was removed..all brass was in the chamber and the bolt wouldn't lock back at all.

I swapped the carbine buffer for the Spikes T2 with the same results!

Ok, I can open up the gasport to #48 (.0760) or get an H2 buffer and try the test again?

[MarkG]

Took the #50 (.070) bit and cleaned up the port (went in by hand)and then used the #49 (.0730) to open the port. Gas port mics out at .072 and now back to the range.

Your gas port "mics" out at .072? How did you fit your micrometer in the hole?

You have no idea what your gas port size is at this point. Drills don't make round or smooth holes (especially wire gauge drills), reamers do. Keep experimenting, it makes for good reading.

[markm]

I swapped the carbine buffer for the Spikes T2 with the same results!

You're using two unacceptable buffers for the barrel length. I'd throw the Spikes nonsense into the closest lake and get an H2 and H3 buffer.

Quit openning the port up. That's a non-reverseable experiment.