If it's a bolt gun then you don't need enough pressure to cycle an action. That's one less variable you have to worry about and you should be able to make it quieter. Just make sure that whatever powder you choose fills the available case space to at least 80%, so as to prevent Flash-Over and SEE. Bullet shape and seating depth affect available case space so I use the software Quickload for this.thresk wrote:^^Thank you both for the great info, I should have mentioned this is for a bolt rifle, using W231 powder as it's the fastest I have on hand.
dellet wrote:Bullet flight noise will be determined more by bullet shape than anything else. The 168 Lehigh will probably be in the running as one of the loudest.
What other factors besides ballistic coeff. do you need to look at? I just figured the higher the bc, the quieter but idk.
Hmm didn't know the pressure was so similar, might have to look at some heavier bullets (don't want to go lower as it will need to take down hogs up to 200lb).Klem wrote:The muzzle pressure (sound) between a 168gn and 220gn is almost the same so you won't save any sound at the firing point.
I'm thinking BC is a clumsy indicator of bullet flight sound. BC is a function of two variables; drag coefficient and sectional density (mass and diameter). Drag coefficient or how the bullet travels through the air would be a good indicator of sound but mass and diameter are not. Some bullets are designed to minimise drag coefficient, for example 'VLD' (Very Low Drag) so they would be a good choice for being quieter in flight. My experience with hunting subsonic is not to expect the bullets to do very much when they hit, regardless of design. Essentially the Blackout is an accurate .45ACP handgun. Shooting 220gn at subsonic speeds...it's the same as a Colt .45. You have to stalk up to 100yards when using subsonics so it's even more like a handgun round. They kill by crush trail only. There's no temporary wound cavity and kinetic shock. The bullet rarely comes apart and if it does don't expect it to have much effect on the animal. Videos of impressive ballistic gel tests and how many water jugs get penetrated are a far cry from my experience...It's like bow hunting. It's all down to getting close and accurate shot placement so you may as well use a target bullet with low drag. I prefer 220SMK's because they have the added benefit of tumbling on impact. At least that's something more than laser-beaming through the target.
Most likely the loudest sounds are going to be the 'slap' of the animal being hit and the 'zing' of the ricochet as it exits the other side. If you miss and the bullet hits the ground or enough foliage it often tumbles so there's a 'zing' sound that will spook animals. Heavy, slow bullets tend to do this. Also, the animal reacting suddenly when hit tends to panic the rest of the sounder or herd. Not much you can do about the slap, or zing or what the animal does when hit except accurate shot placement. In lighter animals the bullet always exits so you get an audible slap followed by a zing off into the distance. I've tried almost all of the heavy subsonic bullets including Blackout Bullets and Outlaw State and they all act like monoliths. Recovered bullets are dented but that's about it. All this activity at the traget never fails to spook the nearby herd so you only get one shot. Plus don't forget you will be no more than 100yds from your target so they might already know you are there and are primed to run at the slightest excuse.
Unsure whether you have any influence over this but the longer the barrel the lower the muzzle pressure when the bullet exits the muzzle. The more barrel volume the more space there is to contain the pressure and cool the expanding gas. Like Dellet says, choose your powder carefully to give you the lowest muzzle pressure for 1,010fps.
What is the length of your barrel?
