Adj. gas block vs heavier buffer for suppressed use.

AR/M4 AR Technical Discussion
1

What’s the general consensus on using an adjustable gas block vs using a heavier buffer or an a5 kit with an h3 or h4 buffer?

Upper in question is a bcm elw 16" mid length barrel and a spikes bcg. Just bought the m4-2000 on 1/15 so I’m going to go ahead and get everything set up for suppressed use. Intending on using the rifle suppressed at least 80% of the time.

Was planning on getting the bcm a5 and an h2 or better anyways but wanted some opinions of this that have messed with this kind of stuff.

Any help is appreciated!

2

Before answering your question, I think you need to look into the effects of putting a suppressor on an ELW barrel.

While it certainly won’t kill you, it is not the most ideal setup and you can expect pretty large POI swings going back and forth. I even notice a big difference on an 11.5" LW compared to a standard profile 10.3".

The designer of the ELW profile has even stated the same. I’d find the thread but I am on my phone.

To answer your question, I would go with both an A5 and a Syrac adjustable block. The A5 is the new standard.

3

What Eurodriver said. Std A5 buffer and a Syrac gen 2 or SLR Sentry series set screw, melonited.

4

That’s the first I’ve heard of the SLR Sentry, and that looks mighty nice. I like that it is a bit more simple than the Syrac.

5

My consensus of one is that it is cheaper, faster and requires less manual dexterity to throw in a new buffer vs. doing the gas block swap.

However, for 80% suppressed if you need the gas block it is probably a smart thing to do. I would see how it shoots first, before making that trip.

ETA: if I am building up a lower I always use the A5 as there are very few reasons not to use one.

6

If you can, could you get me the link of when the designer said that the elw profile is not ideal for suppressed use? I’m not saying you’re wrong or anything, I would just like the reading material!
I wish micro moa would release the govnah for 625 barrels

7

Also, does anyone happen to know if either of those adjustable gas blocks will fit unobstructed under the KMR rail? Also, which model would be needed for my SBR. Im running an 11.5" BCM BFH SBR with 10" KMR and run it suppressed almost always. There is significant gas blow back and I want to reduce the wear and tear as much as possible.

Also saw that Gemtech is releasing a new BCG designed to eliminate the need for an adjustable gas block, but it is pricey at $250.

Thanks.

8

I have the same set up with the SLR Sentry premium gas block that’s under a KMR. 1500 suppressed rounds through it to date and no issues. I run it suppressed 99 percent of the time. H2 and car spring with gas block open 4 clicks from closed. Runs like a champ with and without the can and 5.56 ammo.

9

Does the gas block have any clearance issues with the KMR rail? Any contact? Is it a simple clamp on or does it require any dimpling on the barrel to install? Did you go with the Sentry 6, 7 ,8 and clamp on or set screwed?

Thanks again.

10

Sentry 7 set screw under a KMR. No clearance issues. Plenty of room on all sides.

11

Thank you.

12

Np. I love mine, btw.

13

Was there any need to replace the gas tube with the adjustable gas block? Simple installation?

14

If you bend or crush the original, then replace it. If not, use it again. Just use a new roll pin…those are always single use items.

I use some green penetrating Loctite (not the sleeve retainer) to get a really solid gas seal around the rear of the gas tube from the start. I just put a little on the tube with a cue tip prior to install, on the part to the rear of the gas port. Both the Syrac and SLR are closed at the front, so all the gas pressure is sealed in the block…no carbon under your rail.

15

Probably going to get an slr sentry 6 melonite like buford said along with the bcm a5 really and either an h3 or h4 buffer. Sound like a solid plan?

16

I’d stick with the std A5H2 buffer weight if you’re also getting an adjustable gas block.

17

You can set up an AR to be used with a suppressor by simply adding a heavier buffer but it’s far from ideal. A suppressor works by delaying the time it takes the barrel to vent the gas pressure down to atmospheric. Since the gas system doesn’t reach operating pressure until after the bullet exits the muzzle, the extra pressure causes the port to flow more gas resulting in quicker acceleration of the carrier. Adding more mass to the buffer will slow carrier acceleration, but does nothing to control the gas flow. More gas means more gas to the shooter through the carrier vents and out the gas tube and into the action after the key separates from the tube.

The gas flow through the system is the foundation of a well tuned AR. When adding a suppressor, the flow must be reduced, either by installing a barrel with a smaller gas port or the use of an adjustable gas block

18

Exactly.

One other option to correct gas flow for dedicated suppressed use besides a small gas port is a longer gas system.

19

Must be or should be? Just asking because I’d guess 99.9% of suppressor users do neither

(I’m also a suppressor user holding out, but thinking about an adjustable block)

20

Perhaps “can be” would be the most appropriate qualifier for methods to reduce gas flow in an AR15, suppressed or not. The “must be, or should be” is up to the end user of course. Some will see is as an ‘ought to’, others will see it as a ‘need to.’ Yes, they will work with a suppressor and without and under-sized gas port, or adj. gas block, but at the expense of increased cyclic rate, fouling, and exhaust gas in the shooters face.