SBR, adjustable Block and Cans

[bigkracka]

Will a SBR run fine with/without a can, or will I have to swap parts? Are adjustable blocks considered combat reliable?
I'm considering a M4A2 commando 11.5 w/o a can. If I decide to put a can on it am I going to get into trouble?

[opngrnd]

I believe one of our members uses that gas block with a suppressor. He will probably be along shortly too chime in.

Paging BufordTJustice...

[Singlestack Wonder]

I run a BCM 11.5" with no adjustable gas block with a standard carbine spring and H3 buffer. Runs great with/without suppressor. Also have a 10.5" setup the same as the 11.5" that runs great suppressed/non-suppressed.

While adjustable gas blocks do work and allow for more fine tuning, everyone I have used have become stuck with carbon in short periods of time. Of course, if it is adjusted to the specific rifle and the rifle runs fine, there is no need to adjust it again unless the rifle parameters change.

[Aaron_B]

I have a cut down 16inch colt barrel to 10.5 with adjustable gas block. I have had zero issues with running suppresser or not. It runs and locks back every time with suppressor which is on 95% of the time. When it is off it will not lock back on last round as I set the gas to do that.

[tom12.7]

I'd rather use a non adjustable gas block with a dedicated gas port size that supports function for with or without a can using specific action masses for either.

[Bob Sacamano]

Just started looking into this myself. Lots of threads here (why I recently joined). I will summarize want I have found via research/reading (not actual experience).

If you have a properly ported barrel for un-suppressed use, my guess is that it will be fine for occasional use with a can (obviously not optimized, but it should work).

The challenge will be finding a properly ported barrel or having to cut down a 16” carbine gas. A cut down 16” should let you start with a 0.063 port and let you work your way up if needed. Sionics makes a reduced gas port barrel but wont say how reduced. If I were going to buy an off the shelf 11.5” barrel I would not want to start with a gas port larger than 0.065” for a non-suppressed build and 0.050” for suppressed. Just my opinion (and based on a 10.5” barrel and 5.56 pressure ammo).

If you are starting with a large port barrel;

Detent adjustable gas blocks should work but I have read reports of them failing/coming apart. By work, I mean they are set, then left alone. In theory, you could count clicks going from suppressed to non but doubt that is reliable over the long term (just my guess). Easy to install/tune without a lot of assembly/take down.

As mentioned, the most robust solution I have read about is the BRT MicroTune gas blocks. Fixed screw in ports. May take a few tries at $25/port to get the right one but once set, should be reliable. Drawback is that you have to pick a single port size and remove the GB/muzzle device each time you want to change it. Same result could be had by specifying the proper port size on the barrel.

I accepted the fact that you cannot have a gun optimized for suppressed and unsuppressed with a single port. To my knowledge, the only current option for a two port system is the Noveske Switchblock. Found out the expensive way that it is really more of a normal mode/off block (no practical suppressed mode setting). IMO both ports are way oversized for each mode and 5.56 ammo (of course you have to buy it to find out). You could use the small port to choke down an improperly ported barrel for normal operation. I plan to modify the one I purchased. If it doesnt work out, I will be going with a BRT MicroTune system.

Just my internet cultivated opinions.

[Titan74]

+1 on the non adjustable gas block with dedicated port size.

You could also get a can that has very low or no back pressure. Bolt speed would stay the same as it was without a can, and you wouldn't have to deal with increased fouling of the rifle or accelerated loss of lubrication that are typical to traditional suppressors.

[tom12.7]

There are some ways to work around this with a fixed specific port size size. Depending on the variables involved, you could end up with a simple buffer swap that that does't put either end in an extreme and have a wide span of function without operating much different than a baseline optimal non suppressed only H2/A5H2/rifle action type system. Just depends on the variables involved and many of those are chosen.

[Co-gnARR]

For your reading pleasure:
https://www.m4carbine.net/showthread...essed-SBR-Ever

[triggerguard]

I haven't really had any major function issues with standard gas blocks on short ARs. Typical rule is that you'll end up running a heavier buffer (H2/H3). That being said, there's a difference between functioning and being optimized.

+1 on the LMT enhanced BCG mentioned in the link posted. Running one in a 12" build that was a little over-gassed and is much nicer to shoot now.