oh yeah heavier the better. Far as 9mm bcg's i bought a spinta precision blem for $109 and polished it and it has worked flawlessly. it has the removeable weight so you can put a law folder or a silent capture buffer spring in there. Surprisingly enough the cleanest ammo ive found is freedom munitions 135 grain for ~20 cents a around. no where near as much smoke in the chamber as with other cheap rounds through my suppressor
My 9mm AR was filthy
- Thread starter jimbobborg
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jimbobborg
Oddball caliber fan
I tried the rifle again at Peacemaker. It choked through two stages before I got the idea to borrow someone else's PCC lower. The last three stages it ran like a sewing machine.
So it appears that my lower is causing the problems.
His lower is set up different than mine. I'm using a CMMG 9mm lower, with POF 4 lb trigger pack, AR-10 carbine buffer spring, CMMG MK9 buffer, and stock (original) CMMG parts. He has an Aeroprecision 9mm lower, with AR-15 carbine spring, a YHM 9mm buffer, and a Hiperfire 24C trigger.
First thing to try is the parts that are related to the magazine, so I bought a new mag catch and spring. If that fails, I'm going with the trigger swap. If that fails, I'm getting a new 9mm stripped lower. At least I know the upper is working fine.
So it appears that my lower is causing the problems.
His lower is set up different than mine. I'm using a CMMG 9mm lower, with POF 4 lb trigger pack, AR-10 carbine buffer spring, CMMG MK9 buffer, and stock (original) CMMG parts. He has an Aeroprecision 9mm lower, with AR-15 carbine spring, a YHM 9mm buffer, and a Hiperfire 24C trigger.
First thing to try is the parts that are related to the magazine, so I bought a new mag catch and spring. If that fails, I'm going with the trigger swap. If that fails, I'm getting a new 9mm stripped lower. At least I know the upper is working fine.
davsco
Ultimate Member
i know almost nothing about gunsmithing, and maybe my ignorance shows here, but thinking an ar-10 spring may be way too heavy/strong.
- Jul 29, 2014
- 50,068
Most people use then in 9mm ARs along with extra heavy buffers.
jimbobborg
Oddball caliber fan
I get about 90% successful ejection with that combo. The ejecting brass appears to rebound into the chamber and screws things up. It's exactly the same with the 9mm AR spring. I'm testing out my first hypothesis, that the magazine catch is out of spec. It pushes the ASC mags up to slow the bolt down, while the Colt mags are not putting any pressure on the bolt. And I'm getting another complete 9mm AR and swapping lowers. And hey, I'm getting another rifle, so it's a win-win situation.
jimbobborg
Oddball caliber fan
I had a nice transaction with a local patriot and have a second 9mm AR with seven standard capacity magazines (PSA brand). Once I either find my maglula or my new one I just ordered comes in, I'm loading up the new to me magazines for a test run. Hopefully, it's the combination of the ASC mags wearing on the magazine catch that's causing this problem. My next problem will involve a new trigger for the new rifle. It has a nice, 8 lb trigger. And a couple of big latch charging handles. And an appropriate optic. I think the new rifle will be my Steel Challenge gun and my original will be USPSA and Falling Steel gun.
- Jul 29, 2014
- 50,068
Curious. How far do your cases(on a successful string) fly from your position? Do they go far, or just trickle out? Mine kinda trickle out which tells me I have slowed my bolt down adequately to ensure full in-battery firing with as little 'barking' as possible.
Our two guns are apples and oranges as 9mm ARs go, so I'm not trying to make perfect comparisons. I'm just trying to understand the ins and outs of the 9mm AR and problems unique to the platform.
Biggfoot44
Ultimate Member
- Aug 2, 2009
- 33,278
I've got to get enough of a life to test drive my 9mm AR to see what needs tweaking . But MSI on sat, and if I can get free of my usual obligations on Sunday , PP is on deck .
boss281
Ultimate Member
Just to add comparisons, my factory Colt 6450 and 6951 both eject the beejesus out of the cases, often 3-4 benches over. Colt mags and one metalform mag, only problems have been with Winchester 147g WinClean with OCCASIONAL failure to feed, and that's only happened with the last round in the mag.
jimbobborg
Oddball caliber fan
Not as bad as a stock Mini-14, but brass is ejection is pretty brisk. Even with light loads.
- Jul 29, 2014
- 50,068
Seems like(to me) still too much bolt speed?
jimbobborg
Oddball caliber fan
But only with certain magazines
When I switched out the magazine catch, every magazines except the two working magazines fit snug on a closed bolt. With the original catch, they were loose in the magazine well. And when I took the original magazine catch out, the top, where the hole in the magazine is, was metal, no coating left on it.
jimbobborg
Oddball caliber fan
Well, that didn't help. The new AR ran like a sewing machine, the old one did not. I'm switching the buffer and springs out of the new one into the old one. If that works, I'm punching the guy I bought the original lower from. The buffer in the new AR is from Kaw Valley and weighs 7.5 oz. So I'm ordering one of those and the heavy spring. Then I'm ordering a better trigger for the new guy.
What was the M16 you read, "filthy 14" or something? Had 40,000 rounds through it?
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Heck that's not even half a day of shooting! I'll shoot 1,000 to 1500 in a day!
jimbobborg
Oddball caliber fan
I put an order in to Kaw Valley for a 8.0 oz buffer, a 7.5 oz buffer, and a heavier spring. Hopefully it ships today (USPS Priority) so I can have it in time for this weekend's Steel Challenge.
alucard0822
For great Justice
Built a 9mm for PCC competition, haven't messed with many GLOCK compatible builds before this one, but it's a lot of fun. Built it on a QC10 lower and FM sidecharging upper, the bolt carrier weighs in at 14.5oz. I'm just planning to feed it 124gr match ammo that clocks about 1050FPS from my 5" pistol, figure limiting muzzle movement is more important than an overall light recoil. Have been experimenting with buffers and springs, have several buffers ranging from a standard 3oz to a 7.5 oz solid part, and a couple others. Have a few springs in various weights. Found I'm having the best luck for an all around setup with a wolf XP with a 5.3oz CMMG 9mm buffer. I took my time tuning the ejector and extractor, and it has eaten everything I fed it. Made a buffer spacer out of delrin(heavier buffers were extended and didn't need a spacer, and filled the center with soft polyurethane to get the right bolt travel, and it really cut out some of the "slap" from the buffer bottoming in the tube. Getting the bolt hold open to work while not locking open when the mag was used as a support took the most time, lots of tweaks to the linkage. I only have a 5.56 tubb spring on hand, and it works, but a little lighter than the Wolf, and a little harsher recoil, will have to pick up a 308 tubb spring and see how that does, might just be perfect. Finding heavier buffers, especially solid pieces lacking internal weights knock the muzzle a good bit, and feel slow, even though they are really soft shooting, the lighter buffers don't move the muzzle as much.
BE VERY careful when you order a new trigger.... a LOT of them do not function properly with a ramped 9MM bolt.
The hammer MUST be full typical AR15 profile... or it won't reset correctly
I ended up with a ALG ACT with some JP springs.
And I still suggest you make sure your ejector is adjusted properly... and the Tubbs Flatwire .308 spring.
I just read the KAW Vally description on their spring... lets us know how it works out .... I wish they listed spring weight.
- Jul 29, 2014
- 50,068
This is the hammer I'm using in my 9mm(not even sure how I ended up with it). I use it in conjunction with a RRA "improved"(ramped?) bolt carrier. They work flawlessly together.
http://www.republicfirearmsstore.com/product-p/rfar15ssham1.htm
https://www.rockriverarms.com/images/products/rra_940Conv.pdf
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