9MM AR MASTER THREAD

Twinsen · Post by **Twinsen** » Mon Aug 24, 2009 4:56 pm

No. It's all one piece, fancy and smooth.

cyclesarge · Post by **cyclesarge** » Sat Oct 03, 2009 7:00 pm

Finally got to shoot my AR in 9mm confiuration. Functioned flawlessly with 90 rounds of 115gr FMJ. I could only get 147gr FMJ to feed by cycling the charging handle by hand. I thought 147gr JHP would probably not feed either, I dropped the bolt and it mis-feed, cleared that and dropped the bolt again and ran through the rest of the mag with no problem. Does anyone run 147gr FMJ?

Overall I'm stoked, gotta by more ammo and more mags, loading 32 rnds at the range sucks.

Twinsen · Post by **Twinsen** » Sun Oct 04, 2009 3:42 am

I run lots of 147 FMJ. The flat-point kind that is shorter than FMJ.

My C-Products bendy plastic magblock would only allow the feeding of 115s. I bet even though you're feeding those 115's, they smashing against the barrel going in, if bullets a little shorter can't go in. I'd... raise(?) the magblock.

cyclesarge · Post by **cyclesarge** » Sun Oct 04, 2009 12:35 pm

I thought about that. Before I fired the gun the magazines were very tight, so I loosened and lowered the mag block, I'll try raising it back up, now that everything is loosened up a little.

Twinsen · Post by **Twinsen** » Mon Oct 05, 2009 12:20 pm

None of these 147's would feed because the front of my magblock would tip down as it was plastic and could bend. My RRA one can sit higher and feeds them all.

ROFuher · Post by **ROFuher** » Tue Oct 13, 2009 8:58 am

With a HK 3-lug adapter, what is the minimum spacing required between the back of the adapter and the sight tower?

Prince Yamato · Post by **Prince Yamato** » Wed Nov 25, 2009 10:35 pm

Concerning the mags...

I just bought an RRA 9mm carbine with the (I thought it was Hahn, now I'm assuming it is the) RRA adjustable mag block. It came with C-products mags. Two fit fine, one is loose and generally sucks. I tightened the mag catch and that helped a little. In general though, I'm thinking that C-products = crap. I've heard people say good things about the Pro-Mags (which I find hard to believe, as generally Pro-Mags are terrible). Is it true that the Pro-Mags are good?

I'm probably just going to buy some Uzi mags next and mod them. You know the old saying, "If you want something done right, best to do it yourself".

Twinsen · Post by **Twinsen** » Thu Nov 26, 2009 9:52 am

I've only got the C-Products magazines, and they're among the best magazines I own.

cyclesarge · Post by **cyclesarge** » Thu Nov 26, 2009 10:17 am

I picked up 4 C products (2 in new finish,2 in old finish) and 4 Metalforms, they all work about the same. I tried 6 ProMags and they would only feed every other round or so until I had about 15 rounds left in the mag, then they worked alright. Needless to say the ProMags are gone (to a guy that knew the trouble I was having). I think it comes down to what works in YOUR gun

Prince Yamato · Post by **Prince Yamato** » Thu Nov 26, 2009 12:04 pm

Well darn, there goes that theory!

Subgunner · Post by **Subgunner** » Thu Dec 17, 2009 7:52 pm

I have the Hahn top-drop in block on my 9mm carbine. I originally had the pinned in block, also a Hahn block and they both work great.

I had the pinned block taken out and went with the "drop in" when I obtained a 5.56 commando upper.

I use C-products magazines, Uzi magazines and a few original Colt mags. in my gun and they all run great.

I have never had a pro-mag work in my gun, nor any of the 9mm carbines owned by my friends. When you load them to capacity they bulge and will pull the Rock River block out, and you wind up with a magazine/mag. block lolli-pop.

In my opinion you can't go wrong with the Hahn block. When it comes to Magazines, you get what you pay for.

Deavis · Post by **Deavis** » Sun Dec 20, 2009 3:27 am

I bought an OLY 16" A1 style 9mm complete upper at a show complete for $300 with 2 plastic looking (simmunitions style) AR-15 30 rd exterior dimension mags. Sold those for a $100, bought a complete OLY lower and a Hahn drop in the top mag block with paddle release and got a steal on 15 greasy Sten mags delivered for $35 in various conditions... I chopped half the mags down to be 20 rounders. I shot the gun and got one ragggedy hole groups at 25 yards (nice) but even better... the gun works FLAWLESSLY with this system. I never had a stopage in 2400 rounds and gave it to a fellow shooter who shot about 400x and returned it clean (against orders but he is old school, returning things better than borrowed).

Now I am over 2K again with no cleaning. It eats all ammo like pac man eats dots. grimy surplus to 147s JHP does not matter. I crakced it open and it is completely scummy inside. I am going to shoot it til it fails or my form 1 comes back and I have to pull barrel (might as well start fresh).

I thought the little wire ejector would break (bought extras), looking so flimsy but it is a trooper. seriously kicks brass 30' to the right at 3:30. Perhaps an H buffer would help but I dont care.

This gun is up for a Form 1 project for me at 10.5 and add a can as funds become available.

Oly is ALL OVER THE MAP on quality, I think I got lucky and couldn't be happier with price paid (< $600 total) or the performance. Its not as cool as a Colt/RRA... but .... I have no complaints other than no BHO on last shot. Added bonus is all the lower/buffer/spring parts are standard....

Rou · Post by **Rou** » Fri Mar 12, 2010 12:50 am

I purchased a Hahn mag adapter (Top Adapter drop in), and am having 2 problems. The setup I have is:
Spike's Tactical lower and 9mm upper,
a CMMG enhanced bolt carrier
CMMG lower parts kit,
plastic colt style promags and metal cproducts.
The first problem that I'm having is that the magazines will not stay in. The mag catch doesn't hold. I tried using a different mag catch and the mag still drops out when you wiggle it. It seems like there is too much space. The other issue I'm having is that the bolt scrapes the top of the metal mags and actually strips some of the plastic off of the promag followers. Have you seen this happen? What would the remedy for this be?

rob_s · Post by **rob_s** » Fri Mar 12, 2010 6:00 am

Three questions:
1) Did you assemble this lower yourself?
2) Do you have another spare lower sitting around?
3) Can you remove the Hahn device and try it with a 5.56 magazine and let us know how it works?

Rou · Post by **Rou** » Fri Mar 12, 2010 11:27 am

Hey Rob, thanks for those questions! I was able to narrow it down. I did build it myself, and I tried the mag block on 2 other lowers. The first issue of the mag not catching properly wasn't there with a Gator build I have and a LWRC M6A2. Also the Spike's Tactical lower was able to hold a pmag with a very tight fit. I contacted Hahn and they said :
"There are 2 reasons for mags falling out:
99% of the time it is the mag catch, some go deeper than others depending on brand. Contact Rock River Arms for a catch, they deal with 9mms all the time and are well aware of the problem, they sell a mag catch that will work. The other 1% reason is in the lower. The machined slot on the left side of the receiver is not deep enough, it holds the catch out so it won't engage. A gunsmith can machine this out deeper.

The position of the magazine relative to your bolt is dictated by your mag catch. Cproducts has a reputation for rubbing into bolts with some of their mags, on top of their lips and also in between. Current Promags I haven't heard many complaints about. I have no experience with the CMMG bolt or how consistant they are, logically it would be a place to look. RRA and Colt bolts have never had this problem as far as I know, if you can borrow one of these bolts and see if there is a difference. If all else fails you can grind on your mags, a lot of guys do that to Cproducts.

Metalform makes the best mags, rarely do I ever hear of a problem with them. I have some 12 year old ones that work as well as the new ones I have. Other mags are cheaper but you get what you pay for. I heard CDNN was selling them at a good price if they are still available."

So I am going to try getting a metalform mag and also trying to get a RRA mag catch. Hopefully that will take care of the first issue. I really don't want to have to cut out the lower if I can avoid it.

Anyone have any issues with the CMMG enhanced ramped bolt carrier and any experience?

rob_s · Post by **rob_s** » Fri Mar 12, 2010 2:39 pm

Well, they seem to have addressed where I was heading.

You say a 5.56 mag will go in, but it's hard to seat? Starting to sound to me like the slot for the mag release is too high in the lower.

Rou · Post by **Rou** » Fri Mar 12, 2010 3:48 pm

It seats fine, very snug without any issue with the mag catch. The mag catch with the Hahn also catches, but it's not a deep enough catch and the mag drops out if you wiggle it a little.

Twinsen · Post by **Twinsen** » Mon Mar 29, 2010 4:14 pm

My guess is that you can grab a bigger mag catch and all your problems will be solved. That is, as long as you got that Hahn block in there and it fits tight. The CProducts magblock that I originally bought was not a tight fit for any magwell, and it could move inside the magwell front to back as well as side to side because it had so much flex. Side to side movement made it so that you could tilt a magazine, pulling it away from the mag catch and drop free.

You can easily check how tight the magblock is, and how tight your magazines are inside the block.

You can also just look in the lower and see how far that mag catch sticks out past your magblock.

cyclesarge · Post by **cyclesarge** » Sat Apr 24, 2010 2:13 pm

Now I am having feeding problems again. I suspect the bolt is traveling too fast as the bullet is jamming against the top of the chamber. I assume what has changed is that the gun (and buffer spring) has loosened up since shooting around 500 rounds now. I am using the Spikes Tactical ST-T2 heavy buffer ST-9BS Combo and I am thinking about going to the ST-9X 9mm heavy buffer. I would hope this would also help quiet the gun when shooting suppressed as it would hold the bolt closed a little longer. Does this sound right? Or am I barking up the wrong tree?

rob_s · Post by **rob_s** » Sat Apr 24, 2010 9:23 pm

the *top* of the chamber? Odd. Got a picture?

Twinsen · Post by **Twinsen** » Sat Apr 24, 2010 11:34 pm

Yeah, I'm pretty sure the bolt moving too fast jams the bullet into the bottom of the magwell. That is why the M4 feedramps exist, anyway.

I'm guessing your magblock is sitting too high. Or the gun is just too dirty and the bolt is moving too slowly. Before 1000 rounds, I have to do a thorough cleaning because the rounds tip up.

Rou · Post by **Rou** » Fri Apr 30, 2010 1:36 pm

Well I took the 9 down to the range and of course had several issues. First shot was good. Very quiet and felt good. Next shot the hammer fell and no bang. Cleared it and saw that the primer had a slight indent and no more (looks like what i saw in the slam fire section of barfcom). Took another shot and it fired. Went through 2 magazines this way with some firing and some not. I checked some of the rounds that had the slight indent to see if they would fire in my pistol and they fired fine so I know it wasn't the ammo (or guess that it isn't). At one point the bcg seemed to get stuck and I couldn't bring it back to put a new round in. But it became unstuck, so i decided to keep going (probably a bad idea). Also some fo the rounds were not feeding right properly, with the fresh round going perpendicular and getting trapped between the bcg and the upper. The last couple of rounds didn't fire so I decided to call it a day.

Next day, I wanted to see if it was the Armalite 2 stage trigger causing the problem so I put back the regular trigger. I noticed that there was what appeared to be little silver flakes on the bcg, I assumed that it was some kind of fouling from the suppressor. Turns out it was probably the firing pin. Got to the range and nothing happened for several rounds. Took out the BCG and examined it to find the tip of the firing pin was no longer there. I called CMMG and am getting a replacement pin this week.

Anyone heard of that happening? I don't know if it's the Georgia Arms 147 grain ammo that I used or something in the build itself. I'm concerned about using the new firing pin to only have it happen again. Any suggestions as to how I should approach this? The parts are a CMMG enhanced ramp bolt carrier, 9mm buffer and spring (not sure what make besides being the heavy grey one), and a tros 5" barrel.

This project continues to be a headache! It was really fun when it worked, with me getting very tight groups at 25, so I know it's going to be worth it when it's done. ANY thoughts on what I should do next would be appreciated

BriggsRi · Post by **BriggsRi** » Sun Jun 13, 2010 9:59 pm

I took my Colt 6450 9mm SBR out today and was dumbfounded - I could not get it to run to save my life, what gives. I had it out 4 - 5 months ago and the 9mm ran like a dream, no FTE, no FTF nothin nada!

The only thing that I have done since my last range visit was give her a good cleaning - did I not lube her up adequately? Any ideas or suggestions?

Colt 6450 9mm
10.5" BBL
Stock buffer & Spring
Gem-Tech MK-9K can
Fiocchi 147JHP

The darn thing would not properly eject the spent round - the spent round would go high up into the upper receiver and the next round would just jam up underneath of the spent round.

What gives?

chrismartin · Post by **chrismartin** » Sun Jun 13, 2010 10:37 pm

Sounds like you need to adjust your ejector. It's one of the most common problems with 9mm ARs not ejecting the shell correctly. I experienced something similar... First run out was fine, next time I shot it, FTE's everywhere.
If you search this site, I have posted several instructions on adjusting the ejector. You want it riding as close to center of bolt as you can, without causing too much drag.

Found it in the sticky...
Bottom of the page, my post...
ETA: viewtopic.php?t=27944&postdays=0&postorder=asc

BriggsRi · Post by **BriggsRi** » Tue Jul 06, 2010 9:55 pm

chrismartin,

Thanks, I adjusted the ejector and now my rifle runs about 98% - I think that I need to tweak things just a bit more.

It's funny, my little 9mm SBR has a lot more kick than I had thought it should - just a little un-expected

9MM AR MASTER THREAD

3-Lug spacing

OLY

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Question for the 9mm AR Folks - What am I doing wrong?

Re: Question for the 9mm AR Folks - What am I doing wrong?

Re: 9MM AR MASTER THREAD