Suppressor Questions...

meener777 · Apr 2, 2013

I was watching a video showcasing a full auto integrally suppressed AR-15 and it led to a few questions...

First off, he notes in the video that the suppressor kicks gas back into the shooters face. This makes sense since the gas cant eject out the front of the barrel as easily so I assume more goes into the chamber? Does a piston driven action reduce this effect at all? Also, I have heard that subsonic 5.56 doesn't have the kick required to cycle the action of an AR-15, but in this video Mr. Noir seems to indicate that he is firing 5.56 out of the rifle and it sounds too quiet to be supersonic ammo. I have heard mutterings of certain types of loads being able to cycle - anyone know if this is true? Or should I be looking at a 300BLK upper for suppressed shooting? ( <broken link removed> anyone?)

HahnsXD · Apr 2, 2013

Suppressor forces more gas into the gas system, and in a DI AR a lot of that ends up being dumped into the action and out around the charging handle. A piston gun is said to help tremendously. It sounds supersonic to me.

Burt Gummer · Apr 2, 2013

Go 300blk if you want subsonic/quiet. 5.56 subsonic makes no sense. 55-65g bullet flying 1050 or so vs a 220g bullet traveling the same speed, no comparison.

On a gas AR, add a Gas Blocker charging handle, replace the forward assist with a gas vent plug, and even better, get an AR with gas adjustment 0/1/S. 0=no gas, does not cycle, very quiet; 1 normal operation, S - suppressor, less gas/blowback. (Noveske uppers for instance)

TapRackNGo · Apr 2, 2013

Gas comes back and a bit through the charging handle, nothing really that's to bothersome. Depending on what type of suppressor you end up with it sounds like a 22 (longer suppressor) to a bit louder for a shorter suppressor. If you are looking for quiet, 9mm can be very quiet 147gr. You can also shoot some 9mm suppressors on a 300 blackout barrel. So if you already have a 9mm suppressor or 9mm handgun, buy a threaded barrel for the handgun there you go, easy choice. Although, you only want to shoot 300 subs in it (would want to call and verify with manufacturer) I know SWR says its GTG.

I don't have a 300blkout, but considering a barrel. I do not currently reload. If I did I would probably have a 8" 300blkout barrel already.

Burt Gummer · Apr 2, 2013

I have a Universal M1 carbine that I love, which I foolishly threaded and tried out suppressed - now THAT is gassy!

Goggles only kind of gassy.

OREGON FALER · Apr 2, 2013

Burt Gummer said:
I have a Universal M1 carbine that I love, which I foolishly threaded and tried out suppressed - now THAT is gassy! Goggles only kind of gassy.

Glad you said that cause I was thinking of threading grandaddy's m1 Carb.

Burt Gummer · Apr 3, 2013

I should have mentioned about the 223/5.56 subsonic OP question that it makes a lot more sense to build an inexpensive 10/22 w/ a 1:9 twist barrel, KIDD or other lighter spring, Aguila 60g .22lr ammo.

Not a ballistics expert, but there can't be a huge difference in performance sending a 223 55/60g piece of lead down range at subsonic that way vs doing it with a .22lr.

Plus it is mouse fart quiet. They hit hard too, knocks down plates just like the 38g supersonics, or better.

meener777 · Apr 8, 2013

Thanks all for the info. I now have an idea and I wanted to run it by you all. I have an AR build in progress (PSA 16" upper, LMT lower) and I have been thinking of doing this as an SPR. Since it seems like everyone really likes .300 BLK for suppressed shooting and I do plan to get a can at some point I was thinking hmmmm... I wonder if it would be possible to build an SPR in .300 BLK? That way I get an SPR, which I could shoot subsonic for quiet fun, and it looks like all I would have to buy is a barrel. It looks like there are 18" and 20" bull barrels for this caliber. So... questions.

* I have read that .300 BLK has higher energy and hence better ballistics for long range than 5.56 (not much better but better). Is that right?
* How much does barrel length affect accuracy? I assume that having a longer barrel, assuming the powder charge is large enough to fill the barrel with gas, results in a longer period of acceleration for the projectile and thus higher muzzle velocity. How much does having an 18" or 20" barrel affect range and accuracy over say a 16" barrel when using .300 BLK (also, same q in the same question w.r.t. 5.56 as well)?

Any other thoughts on this idea would be appreciated!

.300 bull barrel:
<broken link removed>

p.s. Looked at the Noveske gas adjustment stuff - looks awesome but it looks as though they only make it for 5.56 and 6.8mm SPC.

meener777 · Apr 8, 2013

Some stuff I found about this...

I found some data on muzzle velocity by barrel length, for 5.56. Looks like there is around a 100fps gain from a 16" to a 20" barrel for 5.56, 55 or 62 grain ammo. Based on this data I ran some ballistics simulations and found that the 20" barrel gives you about 50 yards extra distance at a drop of 5 mils on your scope (650-700 yards for 62 grain, 700-750 yards for 55 grain). That doesn't sounds like a huge gain to me, although slap the suppressor on there and that could be another 100 fps or so, maybe another 50 yards (didn't run those ballistics).
<broken link removed>

Also Wikipedia had a bunch of info. .300 BLK is much slower than 5.56 in terms of muzzle velocity (like 700-1000 fps slower for supersonic ammo). I assume that muzzle velocity is important for range since gravity starts affecting the bullet immediately, so the faster you get to your target the less drop you have, i.e. more effective range. After comparing it to 5.56 and even Lapua Magnum (as an example of a long range caliber) I am coming to think that maybe .300 BLK wouldn't make such a great SPR caliber. I'm just learning about ballistics though and its pretty confusing what goes into making a good long range rifle system. Fun to think about though hehe.

Found a thread on 300blktalk where someone asked the same question I did. Responses varied...
300BlkTalk ? View topic - .300blk as an SPR? Or am i just being stupid?

Ranb · Apr 9, 2013

Burt Gummer said:
I have a Universal M1 carbine that I love, which I foolishly threaded and tried out suppressed - now THAT is gassy! Goggles only kind of gassy.

You too huh? I suppressed my Universal (piece o crap) M-1 carbine by setting back the front sight and profiling the barrel for my 300 whisper silencer. I figured that the large volume and lack of a gas tube would make it ideal for suppression. The blow back from the chamber moves my hair back and I need double eye protection to shoot it suppressed. It is the only gun I own that is less comfortable to shoot suppressed.

Ranb