9mm AR woes continue

[Arizona_Mike]

I've posted before about my disconnector problems trying to get my 9mm upper to work with the match grade trigger in my lower (to avoid a second lower and tax stamp). By relocating the takedown pin hole upward slightly, I've reduced the failure to disconnect rate from 100% to below 2% (when the gun is right side up) and I am now 100% confident that the gun will never double when the hammer follows the BCG. I think putting a brass set screw in the bottom of the rear lug has a good chance of solving my problems for good.

Horrible jams: bullets were hitting the underside of the feed insert on my Hahn Precision block. When this happened on the left side of the mag, they flipped nose up when they finally past the ramp and ended up as "compressed loads".

I filed it to be just shy of overhanging the mag now. The last round hold open is now more reliable as the follower is not rubbing on the block. I expect the problem will be fixed. I suspect to get LRHA to be 100% reliable I will have to reduce the hold open spring or remove the extra weight of the BAD Lever. The 9mm mags have a weaker spring than 5.56.

At some point I went from strong firing pin strikes (with some of the holes even looking a little dark/deep) to weak strikes that appear shallow even when they fire. It looks like my firing pin tip chipped at some point also the rear firing pin part is peening over where the hammer hits it shortening the effective hammer travel which is short by design on 9mms).

Also, unless someone has started to make 9mm belted cases, I appear to have suffered one OOB out of 116 rounds fired (into a brass catcher so I know it's mine). I know the gun did not double. The firing pin tip is really rough on the side and slightly peened over so I suspect it snagged.

Quite honestly the CMMG firing pin looks like a monkey made it from a sharpened nail. I hate to see this 9mm project turn into a money pit but I am going to order a Colt 2-piece firing pin and spring.

Anyone know where I can get the Colt OEM parts cheaply?

Mike

Edit: I'm looking on line and don't see a 2-peice firing pin anywhere. Did my pin snap at the transition from the thick to narrow part??? That might explain all the tip damage as well as the OOB! I need to see if the inside of my BCG is chewed up too much.

 

[HJ857]

I have a CMMG upper as well but use the Spike mag block. I am not familiar with the Hahn block, but if it's like the Spike's then you can adjust it's height in the magwell as well as the position of the ejector to allow for a better feed angle. Just something to look at.

If you hand load, maybe try a longer oak, I'm running 1.11 with round nose and HPs, truncated cone do not feed hardly ever no matter what.

The CMMG firing pin is indeed junk and your problem is the same I experienced after about a thousand rounds. I replaced it with the Colt pin and I'm pretty sure I got it at Brownells.

Oh yeah, mine ONLY works properly with the cheap plastic ProMag magazines. I have to enlarge the hole for the mag lock a little, and no other mag will engage the last round bolt hold lever. At competitons I've had people astounded that those mags run reliably, but for me they've been great. Finally, not so sure about the mag spring tension, the ProMags are notably stronger than my 5.56 PMags.

 

[Arizona_Mike]

It does appear that my CMMG firing pin snapped in two somewhere around 50 rounds. I found a RRA pretty cheaply and will see how that holds up.

If the Geissele Hi-Speed (almost 3 times the speed of a regular hammer) beats the hell out of that one or if I cannot get the disconnector nearly 100% functional (I say nearly because it is a plinker/ range toy), I will get another lower with a conventional hammer and SB15 it.

Once you stray too far from 5.56 the modularity of the AR platforms starts becoming more like other guns.

Mike

 

[Arizona_Mike]

I have a CMMG upper as well but use the Spike mag block. I am not familiar with the Hahn block, but if it's like the Spike's then you can adjust it's height in the magwell as well as the position of the ejector to allow for a better feed angle. Just something to look at.

If you hand load, maybe try a longer oak, I'm running 1.11 with round nose and HPs, truncated cone do not feed hardly ever no matter what.

The CMMG firing pin is indeed junk and your problem is the same I experienced after about a thousand rounds. I replaced it with the Colt pin and I'm pretty sure I got it at Brownells.

Oh yeah, mine ONLY works properly with the cheap plastic ProMag magazines. I have to enlarge the hole for the mag lock a little, and no other mag will engage the last round bolt hold lever. At competitons I've had people astounded that those mags run reliably, but for me they've been great. Finally, not so sure about the mag spring tension, the ProMags are notably stronger than my 5.56 PMags.

I'm using the stainless C Products mags which are supposed to be the best. I'm running my block as low as it can go to minimize the amount of abuse it requires to seat a full 32rd mag with the BCG forward. I have not seen any ejection issues but it looks like there is some room to adjust the ejector some.

I will be handloading sometime between now and when I get my Form 4 for my 9mm SMG. I will concentrate on loading 147gr subsonics since I have a can.

 

[HJ857]

What I mean about the ejector is that if you can lower it, then you can raise the block, which in turn will get the feed ramp more in line with the chamber.

Doing that could mean having to enlarge the mag catch hole to get it to lock in easily. Bear in mind that I'm just speculating.

 

[Walkalong]

The mag block must be situated so the rounds feed. If that means it's tight inserting a full mag, so be it. Download a round, or insert it with the bolt back.

 

[eldon519]

I've always heard C Products mags were so-so for 9mm ARs and that Metalform are the way to go. I'm pretty sure that is what Colt ships with the rifle with their own roll-stamp on it. It might be worth getting one to see if that solves any of your problems. CDNN has them for a decent price:

http://www.cdnnsports.com/magazines/ar15-9mm-32rd-metalform.html#.UykOEvldVOg

 

[Arizona_Mike]

As I stated, it appears that my feed problems were being caused by the feed ramp intruding on the magazine space so that the tips of the bullets were scraping against the lower edge of the ramp before they left the magazine. The front of the follower was also doing the same resulting in the final couple rounds not feeding at all and failure of the last round hold open.

I was able to duplicate the jams I was seeing at the range just dry cycling ammo (with the safety on and gun pointed in a relatively safe direction). When I modified the block so that it does not intrude on the inside space of the mag, the jams stopped. Incidentally the LRHO worked 10/10 times for 5 or 6 mags. After I disassembled that mag, straitened the helical set of the spring and stretched the spring a bit by hand, the LRHO started working on that mag as well. So far I have no indication of another feeding problem besides the bullets and follower scraping against the feed ramp edge.

Now that it appears that I have solved the issue that was causing a jam every ~4 rounds, it is entirely possible that I will find other issues but I won't know until I get my new firing pin.

Mike

 

[Arizona_Mike]

New firing pin arrived yesterday!

Status post filing:
* LRHO works 100%
* Jam rate down from. ~25% to 3% (50% on left side of mag to 6% on left side of mag).

I fixed a major problem and now have a minor problem to work on. Most of the jams were on a single 20rd stick and one of 5 32 round sticks had a couple, the other 4 had no jams. I'm going to radius/polish the front edge of the feed ramp.

Mike

PS. Fired 180 rounds and disconnector caught every time.

 

[wally]

Don't do anything radical.
I've found that the 32 round AR 9mm mags are rarely reliable the first few outings -- too much friction in the body initially. I've seen it with AR Stoner, C-Products and ASC.

They work a whole lot better after three or four outings. I've a lot of mags and two 9mm SBRs and we shoot "dueling trees" so its taken some time to come to this conclusion. Using a pro-Mag mag block while one of the Hahn blocks was back-ordered didn't help.

Also tolerance stack-up often shows wear on one of the sides of the magazine feed lips after a few outings meaning the bolt drags a bit which sure doesn't help things.

Mags that I'd marked with a X first time out as jam-o-matic useless were fine the third+ times out.

 

[Arizona_Mike]

When I tightened my Hanh the mag release was binding so I backed it off 1/8 turn. It came loose while shooting. I made sure I filed it just enough that the ramp cleared the mag with the block tight so if it was loose it might have been slightly forward and catching again.

I actually don't mind my Hahn being loose because the right side Colt safety releases the block but my left side Troy safety releases the mag but does not go far enough to release the block. I never ever use the right side mag release wheb changing mags.

I will double check clearances. Something is still catching causing the round to flip up when it comes clear.

I have read that you can dust the mag bodies with graphite.

Mike

 

[wally]

When I tightened my Hanh the safety was binding so I backed it off 1/8 turn.

I'm not understanding this at all. The safety is pretty far form the mag well for it to have much if any effect. I've one top loading Hahn (dedicated because of the PITA of removing the bolt hold open to remove/replace it), and one bottom loading that just slips in like it was a magazine and "wedged" in with a set screw pushing on a roller.


It seems like you are using some kind of ambi mag release setup that I'm not familiar with. Generally you want the mag block as high up as will allow the mag catch to move freely inside the mag block catch cut out. With a top load there is no adjustment, with a bottom load you've usually got a mm or two to play with.

I've never had any real luck with graphite and rounds binding in magazine bodies, usually it came down to smoothing welded seams inside the magazines and/or removing burrs/molding marks from the followers. On the 9mm AR mags it seems the finish is too thick/rough and once it wears off things are fine.

Your failure photo is not the clearest, but it looks like a "bolt over base" failure to me -- the round is late getting into position and the bolt catches the extraction grove instead of the cartridge base which then cams the bullet nose up. This usually means too much friction somewhere in the magazine.

I'm running my block as low as it can go to minimize the amount of abuse it requires to seat a full 32rd mag with the BCG forward.

Actually this has no effect, the mag locks in or not by the position of the mag catch in the lower. This is what sets the height of the rounds relative to the bore and where upper/lower tolerances can wreak havoc. With a bottom loading mag block you usually have a mm or two to adjust the feed ramp relative the rounds when the mag is locked in place. I always try to run them as high as they can go without the ejector dragging on the bolt carrier.

 

[Arizona_Mike]

Sorry, brain fart. I was thinking mag release but typed safety.

On a full mag and the carrier forward, you have to compress the ammo to seat the mag.

Mike

 

[wally]

On a full mag and the carrier forward, you have to compress the ammo to seat the mag.

Yes which is a bear, especially if loaded 32-rounds, such a bear I only load 30 rounds, but the position of the magazine block has no influence on the force required.

 

[Arizona_Mike]

Thinking of just giving up and selling the whole damn thing.

All I did is clean my mags and I am jamming (FTF) just about every round (from both sides of the mags now). Even rounds that make it into the chamber are damaged (bullets pushed in) and show severe pressure signs when fired.

Send an email to Hahn asking for help.

Mike

 

[Arizona_Mike]

Hahn is blaming C-Products and oddly enough the barrel! They also want me to drag the money pit to a gunsmith who will help me shovel even more money in. They also want me to get Metalform mags.

We'll see who C-Products blames . . .

Wish I never built the damn thing . . . I can't say that about any other upper I've built.

Mike

 

[wally]

It doesn't hurt to try a different brand of magazine before giving up.

Its possible you got a batch where the mag catch cutout is a bit too high or too low which could cause issues. Given the problems you've had with getting the match grade trigger to work, maybe there is a problem with the upper to lower fit. If possible I'd try swapping the upper and mag block into a different lower to see if it functions or not.

If you want you can shoot me a PM and send me your mag block and I can try it in mine (assuming its a bottom loading block), let you know if it worked or not, and send it back to you.

I'm also using a CMMG 9mm bolt from Brownell's and its been fine other than the feed issues I'd described with most new mags first few times out.

 

[HJ857]

Did you try raising the entire block to change the angle the rounds hit the ramp?

I see you had some binding of the mag release. I would have no reservations enlarging that hole on the Hahn. It has no function whatsoever other than to allow the mag release button to operate. If moving the Hahn up means having to enlarge that hole, then I'd say get out the dremel and have at it.

Like I said earlier, only the plastic ProMags give me 100% function, that includes a Metalform, a metal ProMag, something else and a metal Brownells mag which works except it won't engage the LRBHO. If I put one of the plastic ProMag followers in the Brownells it works fine, but that's not financially worth it.

 

[wally]

I'd certainly agree with trying to raise or lower the block by adjusting the opening since the Hahn bottom loading model wedges in with a set screw and roller and doesn't depend on the opening for the mag catch at all.

Like I said earlier, only the plastic ProMags give me 100% function,

Funny I've three plastic ProMag 9mm AR mags and they were the best feeding when using my ProMag magazine block (which wasn't very good, ejection issues because the ejector had a lot of wobble) although I did need to remove some burrs and molding marks from the feed lips before they'd work at all. When I got my Hahn block the ProMags wouldn't even fit -- they were fine empty but swelled when loaded to 30 rounds.

With a pair of Hahn blocks all my metal mags seem to work fine, although a fair number needed a few outings to be reliable -- generally bolt over base type feed failures or rounds binding and closing on an empty chamber. I've got like 20 mags, ASC, C-Products, & AR Stoner and have about got them all "broken in". You can see where the finish on the inside is worn away once they start feeding reliably, but its not exactly the same spots on all mags.

But the top loading block doesn't offer the same options as it indexes off a lip on the top near the bolt hold open.

In the wake of Sandy Hook QA/QC seems to have suffered greatly

 

[Arizona_Mike]

There is almost no adjustment in the Hahn block. Very little movement between "top" and "bottom"

I have two Metalforms on the way. The Brownell's C&R discount almost paid for half my C&R already.

Chad from CProductsDefense (which I learned is not C-Products of Newington, CT which went bankrupt in 2011) verified I have the newest version of the old company's mags and said they had poor compatibility with RRA uppers and with some mag blocks, although the 2010 version I have worked in the most applications. He asked me to be a tester for their new mag they are coming out with in a few weeks.

Does anyone know if the RRA upper receiver is dimensionally different which could also be the cause of the issue with my disconnector engagement (which I appear to have fixed)?

I'm wondering if I should disassemble my last build (300 BLK) and test my parts on my mil-spec (minus FA) Ranier upper? I'm starting to wonder if the RRA upper is the cause of all my problems. I was planning putting a Gen 2Syrac gas block on it anyway so I have to remove the handguard. My Gen 1 Syrac currently on the gun is going to my Shillen SDM-R I am building.

Anyway next weekend is spring cleaning (don't want to miss bulk trash day) and I need to work on my taxes. Camping the following weekend and out of town the one after that. Won't have an update for a while.

Mike

 

[wally]

There is almost no adjustment in the Hahn block. Very little movement between "top" and "bottom"

I'm assuming you have the insert from the bottom Hahn block, this is by design, the opening for the mag catch is made to be just a bit wider than the mag catch and should be right most of the time. But if you need it to sit higher or lower, you can open up the slot to allow it to sit where you think it needs to be. Its held in with a roller and a set screw to "wedge" it into position.

It'd definitely be worth trying to get the position right if the new magazines don't solve the issue before you admit defeat.

The load from the top block can't come out from below because there is a tab at the top, there is no adjustment for this model and its not easy to swap out because the bolt hold open needs to be removed. I've one of each type and use the top load for the lower with the 9mm hammer installed. The bottom load is in my "floater" that I use a variety of uppers on.

I'm wondering if I should disassemble my last build (300 BLK) and test my parts on my mil-spec (minus FA) Ranier upper? I'm starting to wonder if the RRA upper is the cause of all my problems.

That would be my first option if the new mags don't fix the issues, or you could try it while waiting for them. But since you've got a bottom loading mag block swapping lowers would be an easier test.

 

[Art Eatman]

OP began new thread:

http://www.thehighroad.org/showthread.php?t=749037