From a .300 blk rifle - about 450 rounds through it. Noticed this about two cleanings ago just said fuck it. Last night tried to use a scotch brite real quick on it and it's not coming off.
Any ideas wtf is going on with the rifle? Not one malfunction or any issues besides whatever is going on here
It’s fine.
If there's no issues then why the fuck are you worried about it? It's not like it's on the outside for the world to see. It's just normal wear and tear.
Your headspacing is a little off, easiest way to fix is to get a lead weighted buffer if you don't already have one to add enough delay in the action for the propellant to burn more completely before it impinges on the bolt
Looks like discoloration when the bolt heats up. Rifle is fine, i’ve seen many a bolt look like this.
This but also sort of this:Basically just really caked on fouling, bro.
Just caked on carbon is all. Still functions? Don't worry about it
Non-critical problem in a non-critical location.
what? how is a heavier buffer going to slow down the gas system? impingement happens before the bolt carrier even moves.
not that guy but in my own experience, in general, heavier bolts and buffers mean longer unlocking times. But you're right and I have no idea whether or not the seals inside the BCG are tight enough to actually do anything there. Weird thought. Never really clicked that it's not all 100% sealed up like an AK, Blowback gun, tilt lock, etc.
true heavier buffer means longer unlocking time as the bolt carrier has to move back to unlock. however was talking about letting the powder burn more completely, which to my understanding requires either less powder or a longer gas system the latter of which is usually a bad thing with .300 blackout ARs.
Please enlighten me if i'm wrong as my .300 pistol (7.5" pistol length gas) bolt gets similar fouling that looks like copper buildup. My best guess is vaporized copper within the combustion gases are getting through the bcg in higher quantities due to the pistol gas system and is probably what OP is also dealing with.
Ok.. lots of good info. Only other ar I have is a 5.56 w 900rds through that and no deposits like this at all so I was alarmed
It's a PSAshit 10.5 w pistol gas system. I asked them and they just auto replied with a RMA and I am gonna be annoyed to send it in for however many weeks since I was supposed to go choot w my pops in a week
I don't see the problem?
to summarize: On most guns having the bolt locked would by nature keep hot gasses and carbon fouling trapped between the projectile and the bolt face longer resulting in a more complete powder burn, but in the case of an AR15 specifically it has an "unsealed" gas system. The buffer might reduce carrier velocity but I realized in that yeah, because of the gas system if probably wouldn't change the amount of carbon too much. Also, a longer gas system is not good or bad with .300BLK, IMO, as long as you have an adjustable gas block. In theory, a longer gas system might be good, as it could offer you the option to load some VERY warm super sonic rounds and still have a very nicely cycling gun. The danger is getting a longer gas system and not being able to adjust the gun to get it to cycle correctly. But I don't know a lot about that, I have two .300BLKs, one is a short as fuck 6" PDW/pistol that I need to tweak and the other is a bolt gun.
You seem new, no bully. And yeah, a 10.5" is gonna have a lot more carbon fouling than a 16" or a 20". The shorter the barrel, the more fouling.
Don't send it in, there's nothing wrong with it and that kind of buildup shouldn't really affect reliability or performance.
If it really bugs you that much, after you go shooting with your dad sit it in a glass cup or jar full of bore cleaner overnight and hit it with a brass brush.
Yeah I'm a newfag, only been shooting like 8 months, two ar platform one in 5.56 one in .300blk that I go shoot every other week...So my only frame of reference for bolt appearance is my 5.56 nearing 1k rounds and bolt is super clean in comparison. If it's just cosmetic and whatever then I'll keep running it.
don't RMA it, nothing wrong with it. the pistol length gas system is for reliability between both sub and supersonic rounds.
>The danger is getting a longer gas system and not being able to adjust the gun to get it to cycle correctly.
This. While i have yet to have my 7.5" pistol length setup fail to feed on me, my range buddy's ceratac upper (10.5" mid-length gas) cannot run subs for shit. He tried a lighter buffer and even cutting loops off of the buffer spring and it still short strokes with subsonic rounds.
>I don't see the problem?
Same, nothing that'd impede function. OP just needs to slime on some more CLP of his choice and continue on.
Send it in? Why? There's nothing wrong with it it, it works fine.
I didn't ask to send it and was skeptical when they asked me to...I just sent PSA the pic of the bolt asking if it matters and they just replied w a RMA form. . Which is why I seeked out the sage advice of /k
Thats their automated reply.
The CS reps don’t know shit about guns.
Most .300BLK guns have issues running subs without a can attached. It's pretty normal, desu, but he should be careful he isn't shooting supers out of a setup that runs subs reliably without a can anyway... or subs with a can, for that matter.
...you know the back end of the bolt is part of the gas system, right? You're drawing a distinction of "unsealed" where there isn't one; the gas pistons on an AK etc. aren't any more "sealed" than the AR-15 is, and those pistons get fouling on them too, completely independent of action timing.
>10.5" mid-length gas
>tapping gas like half an inch from the muzzle
The fuck? Why would anyone build that?
Are you sure you don't mean carbine gas?
Mine run both fine but supers certainly seem to kick harder than they should, I will heed your advice and get and adjustable gas block for it.
>Are you sure you don't mean carbine gas?
It could very well have been carbine length gas, i just remember it was for sure longer than the gas system on mine and it was suspiciously close to the muzzle.
>The fuck? Why would anyone build that?
ceratac thats why. they build shit with whatever parts they can get their hands on. would not recommend.
Yeah, but the position of the AK piston means that if you slow down the unlocking time by adding weight to the bolt, then the gas system stays closed for longer, whereas the AR's gas system is still going to put gas into the FCG and what not, unless I'm missing something here and the BCG is actually sealed, which is exactly what I'm unsure of.
In case what I'm saying is unclear, the primary advantage of a longer unlocking time, on say, a blowback gun, is that you get less carbon fouling and shit blown back into the action. On a piston gun like an AK, a longer unlocking time might reduce that very slightly, but not particularly noticeably because the system already directs carbine fouling to the piston chamber rather than the FCG and shit. With an AR I'm not sure there would be ANY "reduced carbon fouling" going on, because if the gas system isn't closed at the BCG end (which I've never gotten a good answer on) then it doesn't actually matter if the bolt is locked because you're still venting gas with carbon in it anyway, right back to the FCG/action. Not saying anything about that as a reliability thing, just that if that's how it works there's literally no point to use a heavier buffer to try to get a cleaner running gun.
If they do it out of the box that's not all bad, although excessive recoil sucks. I was just saying I'd be VERY wary of shooting a gun explicitly set up for subs with a bunch of supers because it would likely lead to function issues or premature parts wear. If your gun can run subs, try running a (very small) number of supers with a can through it. That shit is the real acid test and if you can run subs unsuppressed and supers suppressed then the gun is basically good to go no matter what; just keep an eye out for premature parts wear. Not discouraging you from an adjustable block, lowering your gas pressure when you run supers will definitely reduce parts wear.
t. apologies for text wall
You're probably putting it away wet.
Noted, will keep an eye out for wear/damage when running supers. Sadly only have a .22 can so far so no testing supressed supers vs unsupressed subs yet.
no need to apologize for being informative, these rare threads with useful information are the ones i like.
There’s only a few powders I find are gassy enough to work with subsonics unsupressed
Mainly CFEblk and AA1680
>Basically just really caked on fouling,
this for sure. dont try to attack it with a pick, just lube and continue to shoot
think about that for a second. maybe they have different type of powder that leave different residues. like how one gas station might have a shitload of detergents and additives in the fuel, and another just the basics. outside of mileage and how it runs in shitty weather, you won't really notice the difference till you do an engine teardown, and one has a different color of baked on carbon.
youre dealing with a chemical reactions here. different substances leave different residues behind.
I mean, you're not wrong, but it's almost certainly more that the one gun is a 16" (so probably a midlength/carbine) and the other is a pistol length gas system. Shit ton more pressure involved in shorter gas systems.
the solution is a cryptic bcg
>unless I'm missing something here and the BCG is actually sealed, which is exactly what I'm unsure of.
It basically is. Pic related shows most of how it works but is missing the tail on the bolt for some reason. The area between the gas rings and the tail make up the expansion chamber for the piston that is the bolt/BCG assembly. Like a AK it's basically sealed until the bolt fully unlocks where the gas then gets vented out holes because the piston is no longer blocking them.
guys I completely made all of that shit up about buffer weights and action timing and powder burn
I thought you died, giddy.
Looks like rust
i wish
Yeah, I figured.
all of you are painfully dumb jesus christ what happened to k