How to make a 300BLK quieter

[ar_noob]

I've got a Sionics SBR lower running with a Rainer 8.5" 300BLK barrel (pistol length) and Fail Zero EXO M16 BCG, under a 7" Seekins Precision MCSR rail and a Griffin RSTA supressor, and overall I'm very happy with the rifle, especially since I switched to the Giessele charging handle and I'm not getting gassed in the face anymore, run flawlessly all four ways so far, but I still kinda expected it to be quieter suppressed with subs.

I'm shooting Sellier & Bellot 220gr 300AAC subsonics, its just about quiet enough to shoot without hearing protection but the action is still pretty loud, sounds kinda like someone hitting something hard with a hammer, it echoes, especially now we have snow on the ground and no leaves on the trees.

Any upgrades I can make to get this closer to suppressed 9mm quiet or am I already as good as I'm gonna get with this platform / caliber combination? Would one of those rather pricey supressor specific Gemtec BCGs make a meaningful difference? If I had gone for a longer barrel would it be quieter?

[Lincoln7]

It's interesting that you posted this because I built a similar 300BLK SBR using (what I assume is) the same 8.5" barrel from Rainier. I'm running an AAC SD-N6 suppressor and even with subs it seems louder than anticipated. The barrel I'm using is 5R rifled. Is it possible that whichever "subsonic" ammunition I've been using aren't truly subsonic due to the increased velocity from the rifling? That's the only theory I can come up with so far.

[asolo]

The only change I can think of is a captured buffer like what JP has to offer but from what I understand it's more of a difference to the shooter since they are in direct contact with the buffer tube. I don't think it makes much if any difference from a distance.

As far as the actual bolt noise- what you're hearing is inherent to a semi-auto bolt cycling. If you want quieter, go bolt action.

[daniel87]

The best way to get the quitest is to reload. Make a some ammo from the top to bottom of the sub loads. start with the top load and shoot them untill the gun doesnt cycle. Then use the load just above the one that doesnt.

Purchased ammo needs to cycle all guns. It is not as quiet as home rolled

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[ar_noob]

Thanks for the responses!

I have a VLTOR A5 buffer with 7 position B5 stock on it so I think (but am not sure) that it uses a non-standard spring and buffer length. I'll check, because I have a Geissele coiled wire buffer spring and buffer left over that is great at getting rid of the AR 'sprong' that I could use in it if the A5 takes standard length.

Any opinion on the Gemtech Suppressor-designed BCG? Lotta money to spend if it doesn't help so I'm loathe to just try it without some 3rd party experience.

The noise definitely seems to be coming from the action not the muzzle end. I wasn't expecting suppressed 22LR quiet but I was hoping it would be close to suppressed 9mm subs quiet, I've heard a suppressed MP5 in 9mm and it seemed much quieter than mine is. Will try doing seem reloads see how much I can improve it while keeping it reliable.

[mic2377]

First step is to reload. I have found my reloads to be quieter than factory ammo. I think you will find good results with this.

It may also be a bit louder as a SBR. I found my 16" to be louder than my buddies 8.5". No, I dont have any scientific meter data on this, but I think it is due to a more complete burn.

It is interesting that your issue sounds like it is port noise. I imagine this would respond to a faster burning powder.

[MegademiC]

I would try running the heaviest buffer that will cycle silenced subs. Sub 300blk was 5-10db louder at the port than muzzel in one of silencer shops vids.

[ar_noob]

I would try running the heaviest buffer that will cycle silenced subs. Sub 300blk was 5-10db louder at the port than muzzel in one of silencer shops vids.

You know if the VLTOR A5 takes a standard length buffer spring and buffer?

[daniel87]

Im 95 percent sure it is not. I belive the spring is rifle and the buffer is a step between rifle and carbine. On their web site they say it only works in the a5

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[ar_noob]

So that option is closed, because I really like the 7 position B5 stock. I'm seriously considering the Gemtech Surpressor bolt carrier. It's just $220 is a lot of money when it doesn't even come with the bolt.