Subsonic 300blk suppression issues

Hello all, I’ve got a howa mini 300 blackout, I’ve shortened the barrel to 14”, got a load that’s very accurate and subsonic (190sub-x, converted 223 brass, once fired in this rifle and resized, win 296 powder). My problem is it’s still pretty bloody loud, certainly more so than I was expecting. I’ve tried three different suppressors (brand new dpt, sonic ghost 40, and another larger diameter sonic), I’ve tried getting the loads way down to 700fps, several different projectiles at 900ish fps (all speeds verified with a chrono, definitely not supersonic). The only other thing I can think of is the dies that came with the rifle are rcbs small base, perhaps after FL sizing some of the gas/noise is exiting out the pressure relief hole on the left side of the receiver, I think I may be clutching at straws here but that’s the only thing I can think of.
Am I just expecting too much out of this round/suppressors? I was expecting only slightly more noise than a 22 but it’s more like a 22mag.
Any light that could be shed on this situation will be appreciated even if the outcome is that I’m a moron than expects too much!
Cheers!

I have a 338br throwing a 300gr sub at 1150fps. It's quiet enough. Depends what environment it is being shot towards

The problem might be the powder you're using. Win 296 / H110 is quite slow burning. Slow powders are used so that there's as much gas as possible to help cycle the actions on the likes of AR-15's. You can get away with using much faster burning powders, with a bolt action. I used AP70, AP100, and Alliant Red Dot which were all very quiet.

Thanks Pommy, very useful info, I was under the impression that 296 was fast enough. I’ll get my grubby little mits on another powder and keep the win296 for super loads when I get around to them. Of the powders you mentioned above have you got a favourite for subsonic blackouts? Or anyone else have any first hand experience?

The noise is breaking the sound barrier by the speed the projectile is traveling, no?

I have similar issues with 2205 16 barrel 9grns with 200 grn proj I think I need a 12in barrel as same load was great in a 10.5 ar15 . maybe the longer barrel increases pressure to much . Maybe not enough pressure to expand case and seal gases in .

Larskramer, Negative, these loads are all subsonic, verified with a chronograph.

Probably Red Dot. I used 5 and a bit grains with the Sub-X. Be very bloody careful with pistol and shotgun powders though - there's no load data to follow.

Make sure you've got realistic expectations. It's never going to be as quiet as a 22lr when there's at least 5x as much powder going off.

This was the conclusion I was coming too, might be worth trying to neck size only some fired brass. But like Pommy said, perhaps my powder choice is a bit on the slow side. Experiment time I think!

Thanks again Pommy,
The reason my expectations are a little higher is this rifle is a lot louder than a mates 16” 308 running subsonic factory ammo (Winchester I think) running a dpt with only two baffles. The dpt I tried today was brand spanking new with all the baffles (4?). I think you maybe on the money with the powder burn rate. I do however realise it’s never going to be 22lr quiet.

4 baffles in my subsonic .45 was loud, 6 baffles is a lot better.

This may not be relevant, so feel free to ignore. I was using Hornady Sub-X factory 300BLK rounds and they were louder than anticipated. Pretty sure some were going supersonic, but that wasn't the whole story.

I got a carbon stealth suppressor on mine with running 190 sub x and shes quiet as a sleeping baby. Can had a big part to play in it

I am shooting the factory sub x in mine most of the time now.
But prior to that I used to shoot the 240 gr SMk.
From the beginning I added two extra baffles on my Dpt.
That did improve the noise. Up to 8 baffles total, you will notice the difference, from 8 to ten the improvement is not so noticeable.
Another thing would be to try a lighter bullet, like the 151 gr cast from Robert ( shooternz on this forum).
The physics of it are :
For a same speed ( ie around that 1030 fps ) you will need less powder to push a lighter projectile than a a heavier one, therefore you will generate less gasses and/or less pressure= a bit less noise.
I have always loaded with vitavuhori n110. The beauty is that I can load subsonic or supersonic from 125 gr to 240 gr.

But yes you could try other faster powders suggested above.

One last thing, shooting in the confinement of the bush makes the sound sounding louder than shooting in an open paddock.

Beware of the ricochet and good luck.

The noise is related to muzzle pressure.
Lighter bullet weights,longer barrels,faster powders will be quieter than shorter barrels ,heavier bullet weights and slower powders.

296 would definately NOT be a powder I would experiment using in lower charge weights.....its the one powder that has multiple warnings against doing so written here there and everywhere......
your not perchance using a magnum primer???? THAT was my issue in similar case doing similar things

there are things that can make it louder like a freshly oiled barrel or certain weather you can get a bit more of a crack

first round pop from too much oxygen in the suppressor

it should be no where near a 22mag so you must be in the transonic zone 950 or lower gives you a little bit of leeway on a hot day

If you are still getting actively expanding propellant gasses out of the suppressor, that will create a lot of noise. Think pulling the hose on an air compressor and the release of pressure from the hose, rather than higher speed phenomena like supersonic crack of the fast projectile etc etc.

One way around this, is much faster burn rate powders like red dot, blue dot, tite group and the faster shotgun culprits. Red dot would be the one I'd be looking at - probably somewhere in the 5.5gr amount will be where you finish up after load development from memory but don't start at that, do the research and find your starting loads for the case and pill. Get a decent load going without the suppressor fitted to confirm nothing weird happens with stability and then work down until you find either the floor at which weird things happen in terms of speed indicating that the powder is getting position sensitive (which I hear is unlikely with red dot as it burns fast enough to not do this usually) or you arrive at your desired velocity. If you are stuck for options I have a spare unopened bottle of Red Dot here we can negotiate on haha.

My Gunsmith says that with subs, the longer the suppressor the better. Volume not so much. If a fast powder is used the total weight / volume of both powder and gas is less and is more easily slowed and depressurized

Quote:

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Originally Posted by Moa Hunter

My Gunsmith says that with subs, the longer the suppressor the better. Volume not so much. If a fast powder is used the total weight / volume of both powder and gas is less and is more easily slowed and depressurized

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More is better for sure but it gets to a point where I could drop 3 baffles and not have a noticeable difference
I’m fully muzzle forward suppressor wise


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well my mate fired his .25/06 from 30ish yards behind me the other day,aiming off to side...maybe 45 degrees so not towards me ,but less than at right angles away..and it was plurry quiet compared to normal..only difference is the extra SS blast baffle from any other time we have used it...

The denser the baffles and tube the less the noise they put out. Weight becomes the operative issue then, thinking the old MAE stainless brick suppressors you could use to jack up a truck here! They were bloody near indestructible and quiet as a mouse in comparison to some out there nowadays, but they damn near doubled the weight of the rifle.

neoprene cover perhaps???

Cast iron ! :-)

Shorter barrel tends to be louder, even 2" can make a big difference in noise level. 14" is a short barrel.
While you may be below the 1100 fps mark that's still a lot of gas coming out large hole in a short barrel. So definitely more noise than a 22mag. Excluding the crack)
a 18" barrel would be quieter but you would need to find someone with one and do a side by side comparison. (thats a good project for someone)
Z

The problem you have isn't helped by the short barrel

Lilgun is my go to powder with a long suppressor

I'm curious as to why would you shorten a barrel then add a muzzle forward suppressor?

I would have thought leaving it a bit longer and using an overbarrel suppressor would be preferable or is there a reason for the muzzle forward?

Thanks for all the knowledge and replies everyone, very helpful. I think I will be looking at a faster burning, more sub suitable powder as recommended by a few. I did not realise win296 is potentially a danger when loaded down, I was going off data found from multiple American sources.
Now that I see where it sits on the burn rate chart compared to what has been suggested here it is indeed too slow, seems to be a good powder for a supersonic load with a 110grain projectile though?
I do realise my choice to shorten the barrel isn’t helping in the noise department, all suppressors I’ve tried are of the over barrel design.
No.3 - I will send you a PM regarding powder shortly.
Thanks again everyone, I will report my findings when I get my hands on a different powder.

I find Trailboss works fantastic with the 110 V-Max subsonic, quieter than my 10-22 with subs & accurate well past 100 on possums etc

Quote:

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Originally Posted by 7mm tragic

I'm curious as to why would you shorten a barrel then add a muzzle forward suppressor?

I would have thought leaving it a bit longer and using an overbarrel suppressor would be preferable or is there a reason for the muzzle forward?

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an inch forward of suppression is worth 4 inch behind the muzz
I wanted short light and quiet