Gas-port regulating gas-block insert install and DIY manufacture.

**dmd08** · 03-29-17, 08:25

Originally Posted by markm

We choked down an LMT 10.5 to .068". It ran like a champ. The recoil impulse still felt snappy with a standard A5 buffer. The ejection pattern and direction seemed to mellow out though.

unsuppressed?

**markm** · 03-29-17, 10:28

Originally Posted by dmd08

unsuppressed?

Yes. Sorry about that. Unsuppressed.

**dmd08** · 03-29-17, 12:12

Originally Posted by markm

Yes. Sorry about that. Unsuppressed.

Hmm. I have a 10.5" that I put a .067" port in and it won't chamber a new round even on a carbine buffer. I'm running a standard m16 carrier and carbine RE.

You're running an A5 and a standard BCG?

**tom12.7** · 03-29-17, 17:07

What base barrel?
For a Colt like barrel with a .067" carbine gas length ported AR with 5.56 ammunition and H2 will run until cooler temperatures and/or drag (fouling, lack of lube, etc) choke it. A porting around .069"-.070" gives a wider span of operation for a 10.3"-10.5" than the reduced porting.
If the system wouldn't run clean and lubed in warm weather for this with the .067" port, I would tend to look into what other issues are causing that before opening up the port to mask an issue.

**Jwknutson17** · 03-29-17, 17:24

Originally Posted by tom12.7

What base barrel?
For a Colt like barrel with a .067" carbine gas length ported AR with 5.56 ammunition and H2 will run until cooler temperatures and/or drag (fouling, lack of lube, etc) choke it. A porting around .069"-.070" gives a wider span of operation for a 10.3"-10.5" than the reduced porting.
If the system wouldn't run clean and lubed in warm weather for this with the .067" port, I would tend to look into what other issues are causing that before opening up the port to mask an issue.

I agree with these points. I run many 10.7 to 11.0 inch barrels with .0625 gas ports and they still run without a can and will cycle with H2/H3 buffers. I would think there is another issue going on.

**markm** · 03-29-17, 20:27

Originally Posted by dmd08

Hmm. I have a 10.5" that I put a .067" port in and it won't chamber a new round even on a carbine buffer. I'm running a standard m16 carrier and carbine RE.

You're running an A5 and a standard BCG?

Good question.... I think Pappabear may have an LMT E carrier in there.

**Pappabear** · 03-30-17, 17:10

Originally Posted by markm

Good question.... I think Pappabear may have an LMT E carrier in there.

yes, E carrier, which would only bog it down more. I have to wonder if chambers and some other features play into the roll of cycling and recoil impulse, vs just port size. I think so.

I was very surprised how the gun still felt. I liked it but thought it would be less snappy. Note this is a bare bones 10.5 with no rail or light or ten other christmas tree items.

Im sold on inserts vs adjustable gas blocks, but thats why we all can what what we want to stay warm and fuzzy.

PB

**tom12.7** · 03-30-17, 18:03

I would hesitate to say that the LMT Enhanced carrier would only bog things down.
The enhanced LMT carriers do change the timing for some events, and we have ways combine them in combinations that take advantages of that.
Chamber, throat, and bore characteristics have a direct effect on the pressure available at the port, among other items aside from the base barrel itself, i.e. specific ammo. Specific ammunition can help determine a characteristic over other possible variables.
When terms similar to "snappy" are used, what is that in reference to? Action bottoming into the RE harshly? Cyclic rate seems to quick? An oscillation of the system during a cycle? A combination of some of these? etc..
I'm pretty much sold on proper base porting over attempts to resolve a base port issue regulating the gas externally as a solution. I can see some some circumstances that would include an external orifice for gas regulation to help compliment a more desirable cyclic rate for a lifespan of operation for a proper base porting size. There's too many negatives associated with oversized base porting for most, the high pressure generated erodes more aggressively when the sealing surfaces of the projectile have an opening to escape into and dump that energy into port erosion on the muzzle end of that port.

**jerrysimons** · 03-30-17, 19:50

Originally Posted by tom12.7

I would hesitate to say that the LMT Enhanced carrier would only bog things down.
The enhanced LMT carriers do change the timing for some events, and we have ways combine them in combinations that take advantages of that.
Chamber, throat, and bore characteristics have a direct effect on the pressure available at the port, among other items aside from the base barrel itself, i.e. specific ammo. Specific ammunition can help determine a characteristic over other possible variables.
When terms similar to "snappy" are used, what is that in reference to? Action bottoming into the RE harshly? Cyclic rate seems to quick? An oscillation of the system during a cycle? A combination of some of these? etc..
I'm pretty much sold on proper base porting over attempts to resolve a base port issue regulating the gas externally as a solution. I can see some some circumstances that would include an external orifice for gas regulation to help compliment a more desirable cyclic rate for a lifespan of operation for a proper base porting size. There's too many negatives associated with oversized base porting for most, the high pressure generated erodes more aggressively when the sealing surfaces of the projectile have an opening to escape into and dump that energy into port erosion on the muzzle end of that port.

When you going to start a barrel company Tom? You could sell us properly ported barrels