Thread: Subsonic 300BLK Noise levels

Hi all,

Got around to firing my 300BLK AR15 for the first time tonight and I'm a bit concerned over how loud it is. I was shooting 220gr american eagle subsonics out of a 14.5" barrel with a waitaki engineering can and the rounds sounded like a supersonic 22lr/maybe slightly louder. Does anyone have any input on this? Is it a case of needing a more expensive can? I've been told the 300BLK can/should be around a subsonic 22LR or quieter.

Cheers,

First put it on a chronograph .or hand load

there shouldn't be a sonic crack for a start . .. also keep in mind the surroundings your shooting in will make a big difference. Completely open areas are best, enclosed or anything that noise can bounce will magnify the sound you hear . . . and to any critters your shooting at.
Most of my shooting is in the hills chasing Goats with a .30cal subs, when the wind is right its almost silent and the biggest noise is the Wop of a hit . .. get in the scrub and there is a definite slow thump that is easily heard - remember a suppressor only slows the gas down, it doesn't eliminate it.
if i was you - if i didn't have a chrony - i would shoot a target at 100 yards, go back to 200 using the same aiming mark and shoot again, then measure the bullet drop, check that against something like Strelok or online.
as an example - mine goes like this -
zero at 50yds
-2.4 at 75
-7.1 at 100
-23.3 at 150
-49.2 at 200
yours should do better that my 197grn. flatpoints but you get the idea, it is a good method if you use good information.

good luck . . .R

With all sub sonic centre fires, the smaller the calibre, the less powder, the longer the barrel & further forward the suppressor goes the quieter it will be.

If you think its loud grab a super sonic 110 Vmax & fire straight after or before a sub & you will change your mind.

Oh I have no doubt my supersonics will be much much louder but I'm still a bit confused as to why people 25/50 metres away from the shooting heard a significant crack... that's not what I was expecting with subsonic loads.

Originally Posted by clavulanate

Oh I have no doubt my supersonics will be much much louder but I'm still a bit confused as to why people 25/50 metres away from the shooting heard a significant crack... that's not what I was expecting with subsonic loads.

You need to chuck it over a chronie with 22 subs for a control velocity.

The name 300whisper also sets this calibre up to fail in terms of expectations. Mine is 16" barrel and is very loud, however its considerably quieter than most other rifles...so I've lowered my expectations to match reality.

Kj

Originally Posted by kimjon

The name 300whisper also sets this calibre up to fail in terms of expectations. Mine is 16" barrel and is very loud, however its considerably quieter than most other rifles...so I've lowered my expectations to match reality.

Kj

Years ago I built a subsonic 308 on a Brno with a big Gunworks suppressor it must have had a 18-20" or so barrel.

With 210 VLDs & Trail boss it was indeed as quiet as a subsonic 22.

It weighed as much as my Rem 700 LSS 300 Rum & didn't kill as well

But it was heaps of fun..... Whish........THUMP

Edit...or did I use Trail Boss.... I did use Dacron filler...maybe it was before Trail Boss... can't remember...getting old....

90gr xtp at 1000fps out of a 22inch barrel with a sonic on the end using trailboss are practically silent. Short barrels will always be more loud as the pressure has not dropped as much before the projectile leaves the barrel.

Just tried out some hornady 208gr and there's still quite a bit of noise there.... I managed to at least hear the bolt this time though

I feel silly for asking this but how likely is it that I/the people ~30 metres away were mistaking the impact into wood as a supersonic crack? Surely it's not that loud? I'm really just trying to come up with answers in lieu of a chrono

Fire it at something hundreds of meters away like a grass bank.

Download a Decibel Meter App to your phone and measure the noise in dB using a subsonic .22 as your control or baseline.

Try and chronograph your loads to ensure the Muzzle Velocity is consistently less than 1080 feet per second so you know the projectiles are not going supersonic.

I like to try for around 1050 FPS average just to be sure.

Cheers
Pete

Gas venting from the ejection port?

Cheers I'll try that. I'm guessing a 22 sub should be ~110dB and the blackout 20/25dB higher than that? based on some googling. Having said that I'm doubtful a phone app is going to be terribly precise? haha.