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I don't know. I'm wondering. When I was at Darrington recently, the boys near me were firing a battery of AR types. They allowed me to scavenge their brass when they were finished. Some of the fired cases were heavily smoked, even back to the head. I wondered why these would be so coked up. Then it occurred to me, one of the lads was firing a rifle with a suppressor. That got me to thinking. Maybe the suppressor didn't allow the bullet to escape down the barrel quite as quickly, so it started to back-feed gas through the chamber until the bullet was clear. We're talking about a very brief period of time. As I understand it, the air in the barrel compresses ahead of the bullet when the cartridge is fired. This causes a bit of resistance. With a suppressor in place, maybe that compressed air cannot escape as quickly. With this scenario, it would suggest raised pressures.

Or: One of their AR's was a short barreled rifle, might this have been the cause of extra-smoked cartridge brass?

Comments?
 
Dunno. When we shoot the SBRed, silenced, AR-15, it seems to blow a lot of crap out of the ejection port:

409987-8b5c34fd6ed5ce21fbe3eb59fdb2130f-jpg.jpg

This last summer, me and my beloved shot this one a lot. She said "why does this one smell like candy?" Haha, it was the grease I happened to use on the BCG. :s0112:
 
My understanding is that there is what you could call 'back pressure' as a gas driven gun with a suppressor may need the gas dialed down, and that is why those guns with adjustable gas systems dial down the gas pressure?
 
Suppressors greatly increase the amount of gas operating the bcg. And also blow back carbon into the chamber and even the magazine. After shooting one round from a full 30rd mag, if you take the mag out and empty it. Every case will be sooty even though they never left the mag.
 
Suppressors greatly increase the amount of gas operating the bcg. And also blow back carbon into the chamber and even the magazine. After shooting one round from a full 30rd mag, if you take the mag out and empty it. Every case will be sooty even though they never left the mag.

Thanks, I guess that answers my question. And also explains why the case heads were all blackened, even the firing pin dimples on the primers.

The brass will be reusable. I cleaned the sooty ones in a mild solution of phosphoric acid, then rinsed, you can't tell they were so dirty.

One thing I read was about a guy who has a Rem. 700 with threaded bbl. for a suppressor. He noted (all with same loads) rifle fired with suppressor, hard bolt lift and a bit of primer flow. Fired without suppressor, normal bolt effort and nothing unusual about the fired primer. So he assumed higher pressures. With the AR platform, sure the case is coming out quickly (there's your soot) but can we also assume a momentary spike of higher pressure? I'm not a suppressor guy, this is just an academic question for me.

I've heard suppressed .223 fired at ranges before, it was pretty quiet. The rounds fired suppressed by the lad at Darrington seemed louder than I remembered. I suppose different devices perform at varying degrees of efficiency and also perhaps there is a wear factor.
 
AR's shiit where they eat and with a suppressor, it's even more apparent. My brass is way dirtier when i shoot with a can. More pressure at the gas block because its not relieved when it leaves the barrel- it's still slightly pressurized (depending on the can) when its traveling through the suppressor. Not exactly more dwell time but the fraction of a second that its traveling through the can allows more pressurized gas and carbon back into the chamber- coating the brass, magazine contents and the bolt as it's cycling.
 
Might I be so bold as to suggest a thorough cleaning out of the relevant articles?

Unlike the perceived wisdom, they DO need cleaning from time to time.

Suggest that the owner starts off the new dacade by doing just that.
 
Fwiw... the AR 15 or AK require back pressure to operate the mechanism. In a standard gun without a suppressor there is about 4 inches between the gas port and end of the barrel. Once the bullet exits the barrel, gas pressure inside the barrel is fully expelled. Adding a suppressor turns this into a 10 to 14 inch area, increasing pressure and dwell time at the port, not in the chamber. This is why an adjustable gas block is desirable on a suppressed gun.
 
If you are intent on shooting subsonic rounds out of an AR , a suppressor can actually be the difference in having a fully cycling action with these lower pressure loads.
 
My sig 320 would blow extractors with a suppressor on, sig told me it was my hybrid suppressor that was the problem.
Switched to a glock and no more problems.
 
I have contemplated this question for a very long time. So I tried some basic limited testing. Measure the dimensions of a factory round fire one round suppressed and one round non-suppressed. I measured both cases after the firing while examining the primer under a magnifying glass. The measurements were exactly the same and the primers look the same. So like mentioned above, I do not believe so but gosh are they filthy no matter if it AR or bolt action.
 
I've heard suppressed .223 fired at ranges before, it was pretty quiet. The rounds fired suppressed by the lad at Darrington seemed louder than I remembered. I suppose different devices perform at varying degrees of efficiency and also perhaps there is a wear factor.

Load vrs. barrel length vrs. type of suppressor being used all very the sound.

A big one is just shooting non-Sub sonic rounds, you get the crack of the bullet going supper sonic. (around 1100 FPS in general)

I load two 300BLK loads, One as quite as I can get it and still operate my piston SIG's, other the fastest I can get the 220grn projectile out of my 5.5" barrel and stay under braking the speed of sound. There is a huge sound difference with the quite loads and the high speed but subsonic loads. (BTW the design of the suppressor also effects it, I have been using a Griffen RECCE7 but few months back got my SIG SRD7 and the Griffen is quieter and provides more gas to operate the slow quite subs)
 
A big one is just shooting non-Sub sonic rounds, you get the crack of the bullet going supper sonic. (around 1100 FPS in general)

This. The guy in Darrington recently was shooting factory ammo, had to be supersonic. I did hear the crack but not much boom.

Come to think more on it, the last one I heard at the range that was so quiet was a .300 BLK. He must've been shooting subsonic. AR platform of course.

I bought a .300 BLK upper and played around with it for a while. It wasn't about suppressed shooting for me. This may sound strange, but I bought it because of the versatility of bullet weights that might be used. I had some light and some heavy .308's that I never figured to use in M1 Rifles or M1A's. I fiddled around with the .300 BLK for about a year, firing everything from 110 gr. to 200 gr. I have a couple of standard loads that I shoot in several different .308 W's, all zero's adjusted to these cartridges. Well, I should've known that the .300 BLK was gonna be fiddly with rezeroing for different bullet weights. And it was. I finally decided that for its capabilities and my applications, I'd let the .300 BLK go and keep going with .223/5.56mm rifles that I've got in that niche. I did get my odd-ball .308 bullets used up with the .300 BLK together with reduced loads in .30-06 in a Rem. 760. It's a hobby, some things float your boat, others not so much.
 
This. The guy in Darrington recently was shooting factory ammo, had to be supersonic. I did hear the crack but not much boom.

Come to think more on it, the last one I heard at the range that was so quiet was a .300 BLK. He must've been shooting subsonic. AR platform of course.

I bought a .300 BLK upper and played around with it for a while. It wasn't about suppressed shooting for me. This may sound strange, but I bought it because of the versatility of bullet weights that might be used. I had some light and some heavy .308's that I never figured to use in M1 Rifles or M1A's. I fiddled around with the .300 BLK for about a year, firing everything from 110 gr. to 200 gr. I have a couple of standard loads that I shoot in several different .308 W's, all zero's adjusted to these cartridges. Well, I should've known that the .300 BLK was gonna be fiddly with rezeroing for different bullet weights. And it was. I finally decided that for its capabilities and my applications, I'd let the .300 BLK go and keep going with .223/5.56mm rifles that I've got in that niche. I did get my odd-ball .308 bullets used up with the .300 BLK together with reduced loads in .30-06 in a Rem. 760. It's a hobby, some things float your boat, others not so much.

Shooting 300blk was designed to be suppressed from the getgo, heck its really the "300 Whisper". So shooting it without a can, allot of its value is really lost that other cartridges can take care of as is, and at lower costs for sure! I get it 100%, it's what you want to get out of it. You're dead on there is a huge shift with bullet weights. I run a two-dot reticle EoTech on all but one of my 300blk. Then stick mostly to those two loads.
 
No, pressures don't increase. The pressure may stay around longer but it does not increase.
 

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