My 9mm AR was filthy

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  • jimbobborg

    Oddball caliber fan
    Aug 2, 2010
    17,112
    Northern Virginia
    When I switched out optics, I had to sight in again. I managed to get it sighted in but I had to single feed every round. Brass would get stuck on the extractor when there was a magazine inserted. Brass ejected fine when there was no magazine inserted. So I decided to clean it last night. My goodness, it's filthy. Like, four paper towels completely caked in gunk filthy. The back of the barrel was black, the chamber was black, and the bore was black. It took half a can of brake cleaner to get most of the gunk out. I obviously need to clean it out on a different schedule than I do with rifle caliber ARs. I'm going to try to get to the range tonight and ensure that it's running, as I have a USPSA match on Sunday.
     

    bkuether

    Judge not this race .....
    Jan 18, 2012
    6,212
    Marriottsville, MD
    Well, yeah.

    With the 9MM being blow back, it did as advertised.

    My KelTec subby in 9 gets gunked up pretty badly after just two range days. Can't imagine an AR that you have run over and over again. Yuk. ;)
     

    jimbobborg

    Oddball caliber fan
    Aug 2, 2010
    17,112
    Northern Virginia
    The flash suppressor has burnt powder caked in it. I don't have a brass brush on hand that will clean it out. I'm replacing the suppressor with a brake later this year, this make me question that decision. Getting the gunk out is hard enough with the fairly open bird cage.
     

    j_h_smith

    Ultimate Member
    Jul 28, 2007
    28,516
    Yep, that blowback design makes for a filthy firearm. Those are the only firearms I clean after every outing.
     

    boss281

    Ultimate Member
    Apr 14, 2012
    1,575
    Carroll County
    The flash suppressor has burnt powder caked in it. I don't have a brass brush on hand that will clean it out. I'm replacing the suppressor with a brake later this year, this make me question that decision. Getting the gunk out is hard enough with the fairly open bird cage.
    Yeah, gunky for sure. I have an older Colt. I shot ~ 300-400 rounds a month the past few months on the bench, getting a feel for it priir to competition. It doesn't take long to get "filthy". I run a cord 9mm Hoppes bore snake through it after a session but have only really cleaned it once this year. And i am talking mostly spraying clp in the upper and lower and wiping or blowing off residue with compressed air. So far so good.

    Sent from my XT1254 using Tapatalk
     

    boss281

    Ultimate Member
    Apr 14, 2012
    1,575
    Carroll County
    The flash suppressor has burnt powder caked in it. I don't have a brass brush on hand that will clean it out. I'm replacing the suppressor with a brake later this year, this make me question that decision. Getting the gunk out is hard enough with the fairly open bird cage.
    Really? I will have to pull it from the safe and inspect it more closely. I dont recall that. Brass toothbrush not helping?

    Sent from my XT1254 using Tapatalk
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,678
    Which is why I wonder on the people never cleaning 22lr. I get the amount of pwder is much less, but I clean mine (10/22) about every 500rnds (about every 2 range trips) and I end up getting a lot of gunk out. I'd imagine with like 4x the powder it would be a lot nastier.

    Much smaller, but I still have heard of people getting the rare OOB detonation on a rimfire and they always seem to be on guns that haven't been cleaned in thousands and thousands of rounds.
     

    Magnumite

    Ultimate Member
    Dec 17, 2007
    6,564
    Harford County, Maryland
    A leading cause of 22 rimfire misfires is caked up residue on the breechface. The firing pin strike drives the rim deeper into the fouling dissipating some of its energy. Sounds like you are describing an extreme case of that phenomeno, except the fouling has gotten hard enough to let more of the firing pin's energy to set off the primer. Might be more of an unsupported case rupture.
     

    davsco

    Ultimate Member
    Oct 21, 2010
    8,607
    Loudoun, VA
    i clean all my guns after each match other than the rare exception. i never want my gear to be the weak link in my game, i do good enough at that... yeah 9mm pcc gets super dirty as do DI AR's. lots of hate on the piston AR's but my LWRC has like 10% of the crap in the chamber my DI AR has after a match, almost a joy to clean.
     

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    I have not cleaned my 4.5" in 4500 or more rounds. I just keep throwing lube on it.

    My son's M&P15 has 22,000 rounds through it and no cleaning. An occasional bore snake and more lube.
     

    jimbobborg

    Oddball caliber fan
    Aug 2, 2010
    17,112
    Northern Virginia
    Even after cleaning it, it still didn't function properly. I saw that it ejected fine with single shots, and it didn't register to check the magazines. Some of the magazines are contacting the BCG, causing it to slow down and not fully cycle. More lube helps, but the two new magazines aren't touching the BCG, and they're working now. I'm heading to Quantico this morning for a USPSA match, hopefully the magazine issue will be resolved.
     

    j_h_smith

    Ultimate Member
    Jul 28, 2007
    28,516
    Run a cotton swab around the chamber to see it there are any burrs. Maybe you have a tight chamber too. Could you post a picture of your spend casings?
     

    rayrevolver

    Active Member
    Jul 26, 2012
    422
    Even after cleaning it, it still didn't function properly. I saw that it ejected fine with single shots, and it didn't register to check the magazines. Some of the magazines are contacting the BCG, causing it to slow down and not fully cycle. More lube helps, but the two new magazines aren't touching the BCG, and they're working now. I'm heading to Quantico this morning for a USPSA match, hopefully the magazine issue will be resolved.

    I bought ASC mags and had to file down the right side feed lips. They hit so hard I couldn't really insert them with the bolt forward.
     

    rayrevolver

    Active Member
    Jul 26, 2012
    422
    What weight buffers are you guys running in your 9mm ARs or DI 5.56 ARs?

    For my PCC I made a custom ~10.1oz buffer and even shooting suppressed it does not seem that bad with respect to filth. Same goes for 5.56, I run heavier buffers as opposed to lighter buffers. Most of the fouling comes from the barrel and a heavier buffer keeps the bolt closed for longer.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,818
    What weight buffers are you guys running in your 9mm ARs or DI 5.56 ARs?

    For my PCC I made a custom ~10.1oz buffer and even shooting suppressed it does not seem that bad with respect to filth. Same goes for 5.56, I run heavier buffers as opposed to lighter buffers. Most of the fouling comes from the barrel and a heavier buffer keeps the bolt closed for longer.

    I have an H-3 buffer and a Tubb's .308 flat spring in my 9mm. Runs pretty smooth. .556, pretty much standard carbine wt. buffers with Tubb's .556 flat springs. Same in my 300AAC except with a Tubb's 300blk flat spring(for the most part, these are all suppressed SBRs).
     

    rayrevolver

    Active Member
    Jul 26, 2012
    422
    I am running a rifle spring in my 9mm with a Vltor RE. The "custom" part of my buffer was me cutting an AR-10 Rifle buffer to the equivalent of A5 length buffer + 0.75". So far so good. I ran a quick 10rds suppressed today and got gassed pretty hard... and then I remembered my forward assist is still a big hole. Probably going to buy a delrin plug.

    Honestly, I went full science project for my suppressed build. 11.5 Mid with an LMT E-carrier & adjustable gas block, and I still end up running a Vltor A5H4 with a stock rifle spring. I tried to tune for an A5H2 but the clicks on the SLR block didn't quite get me there. Seems to tame the gas pretty well.

    EDIT: I guess I need to retract my 9mm PCC statements until I plug that forward assist! Forgot it was the last thing I needed for this build. I assume wide open hole let a lot of gas out that would normally be trapped. I guess the first few times shooting there was enough wind for the gas to be blown away.
     
    Last edited:

    jimbobborg

    Oddball caliber fan
    Aug 2, 2010
    17,112
    Northern Virginia
    I run a 9mm specific buffer. After I greased the bottom of the BCG and used more CLP than usual, the carbine ran fine with the two new magazines. The two old Colt mags still acted wacky, I'm thinking there's a problem with the feed lips on them. Looks like I'm going to have to pick up a few more magazines, I've got too much invested in PCC now to just drop the platform.

    On a side note, I got 20th overall, and got 100% on the fifth stage. So weird seeing my name at the top of a list!
     

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