Got some range time today, finally, with this build that's currently waiting on a Form 1 to come back (filed in June). Not all is well....
The 411: PSA 9mm Colt pattern lower, Gibbz side-charging upper, H3 weight buffer (from KAK, their 5.5oz 9mm buffer), carbine spring and Ti-Rant 45 installed. KAK BCG, KAK 3.5" barrel, ALG ACT trigger w/ whatever hammer spring it comes with (tan, so milspec weight).
115gr Perfecta - flawless through first three mags. Lots of gas though...to be expected.
147gr Federal - first 12-13 rds...flawless. Thereafter, getting some failures to ignite/light primer strikes. No extraction, either. Drop mag, cycle the bolt again and it ignites.
More testing with 147gr....about every 10th round I'm getting no ignition and no extraction. Some rounds show light strike, some none at all. Swapping a 115gr mag back in and flawless through 30rds. I had a couple FTE's and double-feeds on 147gr afterwards, then this:
Out of battery....the bullet landed on the bench below.
I believe that bullet was from the round behind the one that shredded as the nose matches the indent on the primer perfectly (high set primer?)
Buffer too heavy? Its almost like its not cycling far enough to have proper travel for the extractor to lock on place. Or, hammer spring not heavy enough? Maybe both?
Suggestions on solutions? Obvious first fix is to take some weight out of the buffer. Is anybody running a heavier buffer w/ a suppressor?
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I use a 9MM-Q buffer from Heavy-Buffers. It's longer and weighs 8.5oz, much more than a H3 buffer.
Mine is a DDLES Colt pattern lower with a YHM 5" upper, Tirana 45. Always shoot suppressed, it has about 1.5K rounds through it, no issues at all.
I got lucky with everything working 100% from the beginning, so I don't know exactly what your issue might be.
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I picked up a heavy buffer from my LGS, I believe it's a Double Star make, not sure on the weight off the top of my head. I too have been lucky with getting it right from the start. The only time I do have issues with mine is when the oil starts to run dry on the BCG. It will hang up and not cycle 100%, similar to what you've described. It functions without flaw when it's dripping wet.
I am using a CMMG complete lower and I was using a 556 lower with a Hahn mag block, CMMG bolt and buffer with standard carbine buffer spring. No problems with either lower using 4.5" suppressed or 7" uppers.
So, bolt drag could explain some of the issue. The upper was cerakoted and it could be the bolt + 147gr didn't have enough energy to overcome friction. Being brand new, it couldn't have been fouling yet though one mag of 115gr did produce enough gas and soot to be visible. The fourth mag came out a bit wet from blowing lube out.
I'll tear the upper down today and see how rough the interior of the upper is and how smoothly the bolt moves within it.
Mine has about 4-500 rounds through it, I'm hoping it gets better as time goes on. Even through all the blow back I can generally smell when the BCG starts to get dry. The smell goes from a burnt Militec odor to what's best described as two pieces of metal getting hot. At first I was dumping oil on the BCG every 30 round mag to have no issues. Now it's about every 2.5 mags I'm having to oil up the BCG.
Edit - if the tolerances are tight to start with, low on oil and a little fouling I would start there. By nature of the blow back design and coupled with the suppressor, it doesn't take long for these to get dirty.This message has been edited. Last edited by: MattW,
To add insult to (near) injury, my can came apart in the wrong spot.
I was able to carefully separate the end cap from the piston cap w/ an AR15 armorer's wrench and large crescent wrench. Any idea what AAC uses to secure it? Blue Loctite or Rocksett?
Not familiar with AAC, but my Silencerco cans come apart at the wrong spot often. Can be a pain in the ass when it's under a rail too. I try to keep them cleaner these days and a little oil on the appropriate threads to allow for easier separation, but that doesn't always work either...
Yeah....I actually put TW25 on the threads that should come loose right before the range trip.
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Have you fired it unsuppressed with the same issue?
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That's a simple fix! Clean both parts with lacquer thinner, let dry. Then use red loctite about 5-6 drops on the threads. Screw on and off a couple of times to work it in, let set for 24 hours... problem solved.
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