What powder for subsonic 9mm?

[bellavite1]

Recently got my can and I will soon start to reload subsonic 9mm for it.
I read that ammo loaded for suppressor uses typically specific powders to reduce sound signature.
Any truth to it?
How much of a difference would it actually make to the naked ear?
I currently use 700X as it seems to work fine both in my 9mm (4.3gr) and 10mm loads (5.3gr).
I will probably be using 147gr bullets for my 9x19 loads.
Any suggestion on powders that will maximize sound reduction?

[O2HeN2]

I just use WW 231.

O2

[Linkless]

I used bullseye for my first batch but will use VV N310 or N320 in the future. I don't think the burn rate will change the sound much but I could be convinced that faster powder and less of it would be better in this aspect. I'd search for the cleanest burning powder for light loads. Bullseye is fine in my pistols but an absolute mess in my Colt 9mm SBR. Talking full cleaning of the bolt assembly ever couple hundred rounds.

[Great-Kazoo]

Subsonic is usually under 1100 fps. 4.5 - 4.7 gr Unique shows 1k - 1050 fps with a 115 gr fmj, or xtp.

3.8 gr TG shows 1k fps.


Honestly any reloading manual for the bullet you use, has the data.

a 124 fmj-RN @ 4.2 - 4.5 gr Unique, shows 950 - 1,000 fps. well within subsonic loads.


I load 3,3- 3,5 TG with a 147 FMJ. But i can double check those numbers tomorrow.

[bellavite1]

I have loading data, no problem with that.
The question is: all things being equal (bullet weight, barrel lenght, velocity) is one powder quieter than another?
Also, does it matter how much below the sound barrier it is (say 1050 fps vs 850fps) or subsonic is subsonic, regardless of by how much?

[Tim K]

Everything below is educated speculation. It’s probably half right at best.

I think all things being equal, powder might not matter. For the same velocities, the pressure in the barrel is going to be roughly equal when the bullet uncorks at the muzzle and the pressure is released. Barrel length probably matters more than powder by a wide margin. With a semi-auto, it’s only ever going to get so quiet. Port pop and slide noise will contribute a significant portion of the total sound signature and are unavoidable.

[O2HeN2]

The more completely the powder is burned by the time the bullet exits the muzzle, the less combustion you'll support in the suppressor and, at least in theory, the quieter the round will be.

My approach to loading subsonic rounds is extremely complex: What powder do I have on hand? What's the book velocity for the power at different loadings? Then, load to well below 1000fps book velocity. :)

O2

[O2HeN2]

Ya know, there is an argument for using suppressors on supersonic rounds as well...

The supersonic crack of the bullet is heard by a downrange observer as being perpendicular to the bullet's flight. The supersonic crack's misdirection and volume, coupled with the suppressor's reduction in muzzle report masks the origin of the shot since the crack arrives slightly before the muzzle sound, especially on what we might characterize as "near-miss" situations at closer ranges. If there's enough time (read: distance from shooter to observer) between the bullet passing and the muzzle report, this is no longer true.

https://media4.giphy.com/media/WfBZwNA6XSjphkYkzN/giphy.gif?cid=ecf05e4789pu4lbbgu57485vwjadco3y0auo b3w9aexdmlm3&rid=giphy.gif&ct=g

O2

[sportbikeco]

Faster & cleaner powders are what you want.
All things being equal the faster powder should have lower muzzle psi than slower powder for same velocity and use less powder for same velocity.

If you are loading 125's to say 1000 it's not a very high pressure load so some powders may be more "dirty"

Try a book start load of the fastest you have on hand.

[bellavite1]

Faster & cleaner powders are what you want.
All things being equal the faster powder should have lower muzzle psi than slower powder for same velocity and use less powder for same velocity.

If you are loading 125's to say 1000 it's not a very high pressure load so some powders may be more "dirty"

Try a book start load of the fastest you have on hand.

Only one I have is 700X.
How would you say it stacks?

[sportbikeco]

700X is around speed of bullseye on burn chart so it should work well. Would just need to be acceptibly clean and accurate in application.

Start at start load. If subsonic but dirty (or inaccurate or not cycling reliably) add more powder untill it cleans up.

[bellavite1]

Cool, thx!