30 caliber subsonics (308, 7.62, 300-221)

[RWBlue]

Assuming you are shooting different rifles with the same suppressor, or the same rifle with different loads.

Do they sound the same?

What I have going through my mind tonight is, I have my 300-221 AR that is functional (still working out issues).
If I switch powders, build up a load to the same velocity, will I get the same noise?
OR
If I switch to a 308Win rifle, and I build up a subsonic load would it sound the same?

[pug]

Well I will share my opinion but it might not be worth much. I have always experienced that with all other things fairly equal the bigger the bore the bigger the bang. Since you are keeping the same bore diameter and have the subsonic velocity limitation on you I feel the bang is going to be pretty close. Smokeless powder has pretty much the same energy in it (comparing single base to single base) it just releases it at a different rate for the different burning speeds. One area where this will make a difference is if you are shooting a bolt action with a very fast pistol powder like bullseye compared to a gas gun shooting a powder that is slow enough to cycle the action. The fast burning subsonic load will be noticeably quieter than the slower burning subsonic load. The fast burning powder has burned up by the time the bullet exits the barrel and the pressure and temperature are not as high. Also there isn't a large amount of smoldering powder kernels entering the suppressor to be swirled and mixed with fresh air only to ignite again inside the suppressor generating a "pop". As for the subsonic 308win the only problem is finding a bulky enough powder to get at a high case charge and still be subsonic but that is covered in another thread I believe. You can go with a 30% charge like some do but if you charge a case and then lay it on its side you will see the powder spreads out making a thin layer that is ignited across its surface all at once by the primer instead of burning from one end to the other. Some make out fine but I don't like the feel of it myself. Don't know if this helps but I was on a roll.

[RWBlue]

What you have said is, what I was thinking.

It may be worthwhile to switch powders for the burn, but it isn't going to get significantly quieter.

[Slug]

The .308 subsonic loads with the faster burning pistol powder should be quieter. Working on some .308 loads with inserts machined out to take up case capacity. Will post results.