With 300blk suppressed, does barrel length matter? (first 300 build)

[hardcase]

CQB SBR (to be used while operating in my moms basement) in 300blk...

I keep straining to see if I can figure out the reflection in his sunglasses. I need an FBI link to do that.

[cdl]

My 10.3" uses 0.2 gr less powder and is noticeably quieter suppressed than my 8.3". The 10.3" is easy to load for, because with the extra dwell most loads just work. The 10.3" still fits in a 28" Condor rifle case so it's really not much bigger. But then, since the "S" in SBR stands for short... I shoot my 8.3 almost exclusively.

[gds]

I can say that in most cases a 8.5 is definitely louder than a 16 with the same load. It is hard to tell between a 8.5 and a 7.5, but I am sure that if measured it would be. And I can also confirm that a 3.75 is without a doubt louder than a 7.5.

[dellet]

I can say that in most cases a 8.5 is definitely louder than a 16 with the same load. It is hard to tell between a 8.5 and a 7.5, but I am sure that if measured it would be. And I can also confirm that a 3.75 is without a doubt louder than a 7.5.

I'm guessing loud would be a relative term

[gds]

I can say that in most cases a 8.5 is definitely louder than a 16 with the same load. It is hard to tell between a 8.5 and a 7.5, but I am sure that if measured it would be. And I can also confirm that a 3.75 is without a doubt louder than a 7.5.

I'm guessing loud would be a relative term

Well, there is loud and then there is blow out your ear drums even with 3 layers of hearing protection.

[alamo5000]

i want to build a specific CQB SBR (to be used while operating in my moms basement) in 300blk...
with that said, My question is there a difference with noise reduction between a 6.5 & 8 inch barrel using factory sub loads?

I’m sure there is no audible difference, but then I can’t find anything on the web regarding this.

Planning to use my sandman k... not looking for the quietest setup...
just and not wanting to blow my ears out in close quarters like with my MK18 upper.

Thanks!

There will definitely be a difference in sound reduction on different barrel lengths. I will go over a few aspects to this.

First the gun, specifically the barrel and it's ammo. The shorter the barrel the higher the pressure. Powder does not explode. It burns. Different powders burn at different rates and have different flash properties. When you pull the trigger the chamber pressure is what it is in a particular round. As the bullet pushes down the barrel those hot gases expand. The farther away from the chamber the less the pressure. There is basically more volume of space for the gas to expand before the bullet leaves the muzzle.

On a shorter barrel you have significantly more pressure than a longer barrel when the bullet leaves the bore.

On a 5.56 a 20" barrel will only have about 5,700 psi when the bullet leaves the bore. Same gun, same ammo, but chop off the barrel and a 14.5" barrel will have 8,150 psi. That gun with a 10.5" barrel will have 11,500 psi. Percentage wise the increases are significant.

In order to mitigate this is to have suppressors that are more efficient at handling higher pressures, but generally speaking the can is the can. The other way is for a careful powder selection that will maximize the burn, get the velocity, and required pressures specific to your barrel.

With my gun if I shoot Remington 220 grain it's LOUD ammo. If I shoot Hornady Black 208 grain it's substantially quieter. I chalk it up to powder selection as paired to my barrel. Similarly a friend of mine was always complaining about his pistol peppering him in the face with 'sand' when shooting suppressed. We had him try a different powder and the problem got eliminated without losing any energy or velocity.

There is a lot of stuff online about barrel length vs pressure and velocity. That stuff does not specifically mention noise levels, but more pressure definitely means more noise. It's not completely linear but the sound level does go up on the base level from the gun, and the suppressor only suppresses from that baseline.

If you are just sticking with factory ammo you would have to just try a bunch and see which ones would be acceptably loud to you.

[Sharkbite]

smustian wrote:
Seangc wrote:
CQB SBR (to be used while operating in my moms basement) in 300blk...

Image


I keep straining to see if I can figure out the reflection in his sunglasses. I need an FBI link to do that.

That is a plate of Jelly doughnuts. You can tell by the smile starting to appear on his (her?) face.