Dedicated Suppressed SBRs – Some questions

[UM-Iceman]

I’m in the process of assembling two SBR uppers/complete guns that will be dedicated suppressor hosts. I believe I’ve largely figured out the component and set up details but wanted to float them here. I’m looking for a sanity check to ensure my thinking is sound and for answers to a couple of outstanding questions.

Some details. Both uppers will be assembled with high quality parts (mil-spec uppers, BCM BCGs, URX rails, and probably BCM barrels, etc). FWIW, the lowers have DD LPKs, mil-spec RE, standard springs, and H buffers (for now). Both barrels will be 11.5” long and wear muzzle brakes. One upper will host a SF SOCOM RC (still pending) and the other will host a Gemtech G5 (had for a few years).

My plan is to run these uppers/guns suppressed 90-100% of the time. If/when unsuppressed, they’ll get fed quality M193 ammo. I may use some weaker stuff (i.e. PMC Bronze) with the cans on. I’m a civilian so these are not work guns. They will get used for carbine classes/training and one of them may eventually turn into an HD gun.

Bottom line, I would prefer that these function unsuppressed (I’d drop down to a carbine buffer if needed) but it is more important that they run without issue and without unnecessary wear (not overgassed) when suppressed.

I’ve read a number of M4C threads about gas port sizing and adjustable gas blocks, including the one about Grant’s dedicated suppressed gun. I’ve come to the preliminary conclusion that I’d prefer a small gas port barrel vs. the other options. I’m currently thinking about grabbing a couple of carbine gassed 16” BCM barrels and having them cut to 11.5”. Assuming the barrels are in spec, that should leave me with gas ports that are approx 0.063”.

So my questions are:

1. Is cutting 16” carbine barrels down to 11.5” the most efficient way to get the right gas port size for this application, and is 0.063” about the right size?

2. Does anyone with a set up like this regret not getting an adjustable gas block instead?

3. My limited understanding of suppressors and back pressure suggests that the SOCOM cans generate less back pressure than most (the Gemtech G5 in my case) cans. Should this be a consideration for me (i.e. should the SOCOM host get a relatively smaller gas port)?

Thank you.

[revrogue]

After doing all of the same research as you, I eventually decided to go with the insertable gas port from Black River, on a standard sbr barrel. These allow you to fine tune your gas system, but are a simpler, and cheaper, option that the adjustable gas blocks. I'm waiting on my stamp, so I don't know how well my personal setup works, but there's a thread around here somewhere with some good results.

[Todd.K]

Yes,

No,

Probably not enough to worry about. There is no practical way to get a smaller port and you can just run an H3 buffer or A5 setup if you want to slow it down.

[UM-Iceman]

I appreciate the responses so far.

Revrogue - I may give the BRT inserts a try if my plan doesn't work well or possibly to salvage another one of my barrels.

Todd - Thanks for chiming in. Really appreciate the input from an experienced industry guy.

MicroMOA - I may come around to the idea of using an adjustable gas block at some point. I'll probably reconsider once I see people get a lot of rounds through some of the existing offerings.

[Pappabear]

Your getting an 11.5 which is right IMHO. Just buy a BCM, LMT, Noveske 11.5 and run a Vltor A5.

Don't buy a 16 and cut.

I have several of the above with zero problems. I have seen no need for a adjustable gas port. They work for people though.

Good luck.

[Eurodriver]

This is my "dedicated suppressed" SBR.

DD 16" carbine length barrel cut to 10.3". Gas port remained the same. I've heard its anywhere from 0.058-0.063"

It also has a VLTOR A5.

My thoughts:

It definitely has less felt recoil, less "gas face" and less violent extraction than my 12.5" BCM w/ standard gas port. It feels extremely smooth. Function is 100% over several years and 10,000 rounds.

With that said, if I were to make another 10.3"-11.5" SBR I would buy a factory DD/LMT/BCM barrel and call it a day or grab a switchblock. The difference is just not great enough to justify having a single shot rifle with the suppressor removed.

To answer your questions directly:

1. Yes. Absolutely.

2. I don't regret it, but I wouldn't own more than 1.

[UM-Iceman]

...snip...

My thoughts:

It definitely has less felt recoil, less "gas face" and less violent extraction than my 12.5" BCM w/ standard gas port. It feels extremely smooth. Function is 100% over several years and 10,000 rounds.

With that said, if I were to make another 10.3"-11.5" SBR I would buy a factory DD/LMT/BCM barrel and call it a day or grab a switchblock. The difference is just not great enough to justify having a single shot rifle with the suppressor removed.

To answer your questions directly:

1. Yes. Absolutely.

2. I don't regret it, but I wouldn't own more than 1.

Thanks. Perhaps I'll assemble just one and then reassess after getting some rounds downrange.

[Magic_Salad0892]

I would cut down the barrel.

If you run the right parts, (A5 system with standard 5.1 oz buffer, and LMT Enhanced carrier) you can get the gun to lock back with the can off.

[Eurodriver]

I would cut down the barrel.

If you run the right parts, (A5 system with standard 5.1 oz buffer, and LMT Enhanced carrier) you can get the gun to lock back with the can off.

Maybe I need the LMT carrier. I remember reading grant talking about it a few years ago but I didn't want to spend the $200 if it didn't work.

I'm very close. My gun will eject spent rounds, it just needs a few more millimeters to pick up the next round. I'm not too concerned with the bolt locking back although that would be nice.

[Clint]

Here is Grant's epic thread
https://www.m4carbine.net/showthread.php?t=33743