Subsonic cartridges

[pigeon controller]

Just to prove my ignorance , I had a conversation concerning subsonic cartridges and we were talking about the burn of the powder . I thought they were slow burning powder so the ignition did not break the sound barrier but I was told they use a fast burn so all the burn is contained in the breach and so reducing the sound. So over to the PW Massive to educate this thick Brummie.

[TIGHTCHOKE]

You have been correctly informed PC.

 

Get the payload moving and burn the small amount of powder, makes less sound more quickly in the first 10 inches of the barrel.

 

I think 1050 FPS is the MAGIC number.

[sitsinhedges]

A small amount of a fast powder creates less gas volume. This is more easily absorbed by any baffles/porting so is less likely to emerge from the muzzle as noise. Subsonic cartridges thru a normal gun are still quite noisy.

 

In reality with my subsonic reloading it's really just a case of using slightly less powder to push a slightly heavier load a bit more slowly, for example 21grains powder x 28 grams shot = 1240fps but 17grains powder x 30grams shot = 1030 fps. You use a slightly bigger pellet to account for the slower speed too. If you just put less powder in you would end up with an anaemic load with unpredictable performance. The extra weight of shot creates resistance that generates pressure so the smaller volume of powder burns properly and consistently.

 

That's my understanding anyway.

Edited February 5, 2016 by sitsinhedges

[Guest cookoff013]

A small amount of a fast powder creates less gas volume. This is more easily absorbed by any baffles/porting so is less likely to emerge from the muzzle as noise. Subsonic cartridges thru a normal gun are still quite noisy.

 

In reality with my subsonic reloading it's really just a case of using slightly less powder to push a slightly heavier load a bit more slowly, for example 21grains powder x 28 grams shot = 1240fps but 17grains powder x 30grams shot = 1030 fps. You use a slightly bigger pellet to account for the slower speed too. If you just put less powder in you would end up with an anaemic load with unpredictable performance. The extra weight of shot creates resistance that generates pressure so the smaller volume of powder burns properly and consistently.

 

That's my understanding anyway.

 

correct.

using loads that have a powder that is pushing its maximum (and maybe more) payload.

i`ve just completed a 42g subsonic (12gauge). sadly i think the pressure is a tad low, but a 4% increase in powder would equate to 10fps or so speed increase.

 

so i`ve done all weights subsonic. (roughshooter helped (alot) with the 21gram lead subsonic)

 

nb, not all subs are quiet, its the gas can break the SB too.

Edited February 5, 2016 by cookoff013

[pigeon controller]

Thanks for your informative replies.

[islandgun]

 

correct.

using loads that have a powder that is pushing its maximum (and maybe more) payload.

i`ve just completed a 42g subsonic (12gauge). sadly i think the pressure is a tad low, but a 4% increase in powder would equate to 10fps or so speed increase.

 

so i`ve done all weights subsonic. (roughshooter helped (alot) with the 21gram lead subsonic)

 

nb, not all subs are quiet, its the gas can break the SB too.

looking forward to the 42g sub recipe