Hey guys I'm new.

I picked up an Mp15 22 today which is a 22LR and slapped my Silencerco sparrow on it. When I shot it the gun sounds like it doesn't even have a suppressor attached. I tried different ammo and its all loud as crap. If I take the suppressor off the gun is just as loud as with it on. I have a GSG firefly 22LR that the sparrow makes almost whisper quiet with the same ammo I used today. I've done research for a few hours but have not found anything that could help. I did find one form that said the bolt may be opening too quickly allowing the sound out that way. I tried slowing the bolt by holding my thumb on it as hard as I can but still the same issue. I researched the gun before I purchased it and others have been able to suppress the rifle with no issues, so I know the rifle should have the ability to be suppressed.  Has anyone else ever encountered this? Any ideas what might be the problem?

Thanks in advance for any help!!

What is the velocity of the different types of ammo you are using?

If not shooting subsonic ammo, it will have a crack sound but something isn’t right if it sounds identical with or without the suppression.

One was 1250, another 1000, the last was 850. It wasn't a sonic crack from hyper velocity ammo, I've had that with my 22 pistol. I also immediately put the suppressor back on my pistol and double checked with all the same ammo. Whisper quiet. But the rifle doesn't even sound like the suppressor is on it.

What ammo exactly are you using?

Keep in mind almost all 22 ammo out of a short barrel (4.5" or less) will stay sub sonic which is probably the reason why all your ammo sounded good out of your pistol. When shooting a rifle with a suppressor you need to use standard velocity ammunition like CCI standard velocity or similar.

Weird, my 15-22 rifle and pistol sound great shooting CCI SV with my cans. No louder or quieter than my 10/22's.

Any chance you could take a video and replicate the issue?

CCI mini mag, CCI quiet, and a bulk box I don't remember the brand of, its supposed to be around 1200 fps though. All three are crazy quiet through my 22 pistol, but through the rifle it sounds like the suppressor isn't even on the rifle.

CCI Quiet should sound good through a M&P 15-22, I would think. I shoot CCI Clean Subsonic 40gr, mostly, through mine, and it’s mostly bolt noise.

Those other two are guaranteed to be loud from a rifle.

I'm surprised it even cycled with CCI Quiet. That stuff turns all my semi-autos into single shots. Air temp and altitude play a big role in when a round goes supersonic. CCI SV is subsonic here only when temps are above 40 degrees. The Quiet is terribly inaccurate out of my rifles.

I get that, however standard velocity 223 ammo still has a muted sound when fired through a can. This has no muted sound, it literally sounds the same with or without the can. I doubt its the suppressor or the ammo, I think its something weird with the rifle but was trying to find out if anyone had similar experiences, but I've been unable to find any cases online even after several hours of research.

My mp15-22 is awesome with the right ammo, I’m skeptical your rifle is the problem. I’d keep experimenting with ammo, I’m a fan of American eagle suppressor. My pistol keeps most ammo subsonic but I have to be more intentional what I feed through my mp15-22

I have an integrally suppressed 15-22.  All I heard is the bolt going home and a weird plastic tube sound.   It was louder in a pistol configuration with my sparrow.  

Have someone else shoot it while you stand by them.   You’ll be surprised how quiet the bang is.  


I think Mr gunsngear has a video showing that the bolt going home is close to 118dB.

Port pop.


Try a new recoil spring.

My M&P15-22 is super quiet with a Sparrow.

It’s a long shot but I had to throw a spacer on mine. The Sparrow has .400” threads and anything longer can cause issues. Think the spacer was like $10.

https://silencerco.com/shop/delta-threaded-rifle-spacer-1-2-28/

I'm not certain I'm able to add anything, but I have the pistol 15-22 w/ the 8 inch barrel and adding any silencer makes a substantial difference.  If I recall, the 15-22 has .5 in threaded barrel portion and as Lothbrok stated, the sparrow may only have .4 in threads.  It's possible the can is bottoming out on the blast baffle, thereby eliminating the blast chamber.  I know that on my 15-22 I use a crush washer to reduce the threaded portion length of the barrel.  Many will say don't use a crush washer as it might not be perfectly machined, I do like the SiCo spacer.

ETA:  OK, so I measured a few guns and cans.  CGD Siren .67 in. to the first baffle, ECCO Salamander .63 in., Mustang .95 in. to the first baffle.  Guns: M&P 15-22 .63 in (from tip of barrel to shoulder), Tikka T1x .5 in., Ruger MK V Lite .4 in., Buckmark pistol .4,Ruger I had threaded .4 in.,

So it is more than possible to get a gun/can combo that bottoms out thereby affecting the sound, but based upon your description that's not your issue.

I use the same spacer on my factory 15-22 barrels.

We have measured the ballistic crack of a .22LR shot from a Ruger 10/22 at 148 dB 1 meter to the side of the flight path. The sound of the muzzle blast with the same rifle/ammo was 140 dB 1 meter to the side of the muzzle. The reason the suppressor seems to work on the pistol but not the rifle is simply because in the pistol barrel (where sound level to the left of the muzzle is around 152 dB) the projectile has not finished accelerating. Max velocity in the .22LR occurs in the vicinity or 10-14 inches.

The speed of sound varies with temperature, and is about 1087 FPS at 32F, 1120 at 60F, 1140 at 80F. Due to a an air velocity change around the bullet, air can move up to about 5% faster around the bullet itself, which means that if you are within 5-7% of the speed of sound you may get the supersonic ballistic crack.

As has been stated by a number of others, your problem is ammunition going supersonic. We have had excellent, consistent performance in all weapons we have tried with CCI Standard Velocity. CCI also makes a load using a 42 gr bullet that is their version of what they loaded for the Gemtech subsonic. Both of these loads cycled all the weapons we tried.