Fat vs. skinny (heavy vs. light) suppressed subsonic loads

[murro]

is there a significant sound difference if you shoot light bullets (lets say 110gr.) subsonically utilizing suppressor compared to fat 200+gr. ones?
When theorycrafting this scenario i can imagine lighter bullets would require less powder to be burned which means less gasses to be needed calmed down.
Also what is the ballistic performance of light bullets compared to heavy ones? i would assume they will slow faster...
EDIT: its 308 ofc.

 

[Near miss]

Go as heavy as your rifling+barrel combination can take it. I do not think you regret it.
That said, if you just want to shoot subsonics for the sake of it or doing a reloading experiment for fun, it does not matter.

They have similar muzzle blast and flight sound to me. I'd say the more aerodynamic ones have less whoosh sound while flying.

 

[st1650]

For accurate and quiet subsonic it’s mostly about powder burn rate and case fill. If you’re using a 308win case, you’ll want to have at least 80% case fill will will mean Trailboss is the most adequate powder. Go with 175 SMK or any bullet that’s not sensitive to seating depth like the Berger OTM 175 if you’re on a 1/10 or 1/11 twist barrel. You might be able to use the 200/208 on 1/10 depending on environmentals. If using 1/8 then 208/220/240 are very good.

If you were to use a small case like the 300blk, then yes a 135 could be quiet than a 208 due to the faster powder, bullet weight and having to use less powder. Even without a can, a 110 subsonic with trailboss will be quieter than a 208 with tinstar/n105 out of a bolt gun.

 

[murro]

ok, so if I get it right if i want o have lowest sound signature I should:

• fill the brass as much as possible - meaning use as fluffy powder as possible?
• use faster burning powder? - so it is done burning by the time it reaches suppressor?
• I'll have 16" 1-10 twist, so basically to focus on having stable bullet for that twist rate and bullet parameters. Do you guys use the twist rate calculators?

 

[Yondering]

Yes, subsonic loads with light bullets can be quieter than subsonic loads with heavier bullets, within the same cartridge of course. The reason is as you said, there's less powder gas and less muzzle pressure to suppress. A 90gr 300 Blk subsonic can be significantly quieter than a 220gr, even if both use fast powders for bolt action loads.

What I can't figure out is your reasoning of calling a light bullet "skinny" vs a heavy bullet "fat" if they're the same caliber; that might be causing some confusion. A .45 is fat and a .22 is skinny, at least to most people I think.

 

[murro]

Yes, subsonic loads with light bullets can be quieter than subsonic loads with heavier bullets, within the same cartridge of course. The reason is as you said, there's less powder gas and less muzzle pressure to suppress. A 90gr 300 Blk subsonic can be significantly quieter than a 220gr, even if both use fast powders for bolt action loads.

What I can't figure out is your reasoning of calling a light bullet "skinny" vs a heavy bullet "fat" if they're the same caliber; that might be causing some confusion. A .45 is fat and a .22 is skinny, at least to most people I think.

yes, i didnt use correct words, indeed i meant same caliber and criteria was weight, not "thickness"
but thanks for confirming the suspicion

 

[db2000]

At the risk of stating the obvious, I’ll add this anyway…
Velocity is the rate limiting factor in subsonic rounds, so you go as heavy as possible to get as much force/energy as possible on your target. Light subsonic rounds don’t make much sense for that reason. 8.6 Blackout and 375 Raptor are extreme examples of pushing as much weight as possible subsonically. They are louder though, as has been stated.
.22 lr subsonic is about as quiet as it gets if that is the goal.

 

[MadDuner]

I still want to figure out how to get my 165gr 9mm rounds to be just under supersonic - without blowing primers out.
I just haven't experimented with different powders enough.

 

[Yondering]

I still want to figure out how to get my 165gr 9mm rounds to be just under supersonic - without blowing primers out.
I just haven't experimented with different powders enough.

It depends a lot on the bullet. What are you using?

A cast bullet takes less force to push into the rifling than a jacketed bullet, so that can help keep pressures from spiking up too high.
I designed my own heavy 9mm and bored a mold for it; it started at 180gr but I backed off to 170gr due to internal case taper issues relating to OAL, and load it to 950 fps with Green Dot. But that bullet is designed to put a lot of the weight outside the case; if you're using a heavy FMJ ball profile of some sort then internal case capacity will be reduced a lot.

Why Green Dot? Because out of a bunch of pistol powders I tried, it had the most muted sound when suppressed without spiking pressures too much. Clays was nice and quiet for example, but was loosening primer pockets at 900 fps - burn rate was just too fast for the application. Titegroup is right there with Clays. You can go much slower, like Unique or Blue Dot, but they sound sharper or louder when suppressed.

 

[MadDuner]

It depends a lot on the bullet. What are you using?

A cast bullet takes less force to push into the rifling than a jacketed bullet, so that can help keep pressures from spiking up too high.
I designed my own heavy 9mm and bored a mold for it; it started at 180gr but I backed off to 170gr due to internal case taper issues relating to OAL, and load it to 950 fps with Green Dot. But that bullet is designed to put a lot of the weight outside the case; if you're using a heavy FMJ ball profile of some sort then internal case capacity will be reduced a lot.

Why Green Dot? Because out of a bunch of pistol powders I tried, it had the most muted sound when suppressed without spiking pressures too much. Clays was nice and quiet for example, but was loosening primer pockets at 900 fps - burn rate was just too fast for the application. Titegroup is right there with Clays. You can go much slower, like Unique or Blue Dot, but they sound sharper or louder when suppressed.

I’ve been trying with Xtreme 165gr Jacketed round nose.
TiteGroup was way too fast, and only got to a little over 700fps before blowing primers.
Unique got to 750fps with the same blown primers.

I haven’t bothered messing with the 165s much since the 147s go 1050fps with TiteGroup without issues.

But thank you.
I may have to try some Green Dot and work on it some.

 

[Yondering]

I’ve been trying with Xtreme 165gr Jacketed round nose.
TiteGroup was way too fast, and only got to a little over 700fps before blowing primers.
Unique got to 750fps with the same blown primers.

I haven’t bothered messing with the 165s much since the 147s go 1050fps with TiteGroup without issues.

But thank you.
I may have to try some Green Dot and work on it some.

Yeah, I doubt Green Dot will help with that bullet. That fairly pointed ball RN shape is not very efficient and takes up a LOT of case capacity - besides the fact that there's very little point going to such a heavy bullet with that type of FMJ profile, unless you're just trying to ring steel a little louder. The gunshot won't be any quieter than a 147gr subsonic, and it's pretty ineffective on meat, passing through about the same as a 147gr subsonic RN. My recommendation is to choose a different bullet.

If you're dead set on using the (IME inferior) plated bullets, a flat nose profile like this will give you a lot more case capacity. Don't assume the diameter is a problem either, but if you have a CZ for example with a pretty tight throat then you can buy a cheap Lee sizing die and size these down. https://www.xtremebullets.com/38-158-FP-p/xc38-158fp-b0500.htm

Although personally I suggest stepping back to a 147gr like this one for easy loading, especially until you get a better feel for the peculiarities of heavy bullets in the 9mm. https://jamesbullets.com/product/9-mm-rnfpbb-crb-147-gr-new/

As you can see in the pic below, the heavy 9mm bullet I'm using (170gr) has a wide flat nose with as much weight as possible outside the case. Even so, I still have to sort brass by headstamp to eliminate those with more internal taper; I pretty much only use FC and Blazer brass with this bullet, anything else tapers the bullet base (as I guarantee your 165gr RN bullets are doing) and often causes neck tension and seating depth issues.