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9/16/2019 10:09:13 PM
Posted: 3/6/2014 5:36:12 AM EDT
[Last Edit: 5/10/2014 7:50:46 AM EDT by heavyduty]
Hahn block installed, more work in progress - see page 2.

I built a dedicated 9mm carbine about eight years ago using a VM HyTech mag block and RRA bolt. It's always run very, very well.

Lately I've been considering lightening this carbine up. A key part of this would be replacing the VM HyTech with an internal mag block, and replacing my 10 Uzi mags with Colt pattern ones or having the Uzi mags cut.

I'm thinking a Hahn Precision dedicated mag block: http://shop.hahn-precision.com/Dedicated-9mm-Adapter-A9CSRD0405.htm I've worked with Dustin Hahn in the past and have always been impressed with his products.

Any comments on the Hahn, or other suggestions?


(Edited thread title to make more current)
Link Posted: 3/6/2014 9:11:48 AM EDT
The Hahn works great. There is a video on YOutubes on how to cut the Uzi mags. I did 8 with a Dremel in very short time.
Link Posted: 3/6/2014 7:09:55 PM EDT
I didn't realize the mags were that easy to cut. You're getting LRBHO with yours?
Link Posted: 3/7/2014 7:27:22 AM EDT
There's no tab on the Uzi follower for LRBHO.
Link Posted: 3/7/2014 2:38:21 PM EDT
Somewhere on the internet there was and maybe still is a writeup with pics that shows how to put a BHO lifter on the Uzi mag follower and mod the mag accordingly. Looked like more trouble than it was worth to me, but I'm not bothered by the lack of BHO on guns.
Link Posted: 3/8/2014 4:24:56 AM EDT
M60Joe does them.

Link Posted: 3/8/2014 8:42:15 AM EDT
It's not a huge deal if I have to move over to Colt pattern mags, I really do want LRBHO.

Good info - thanks!
Link Posted: 3/8/2014 10:04:23 AM EDT
[Last Edit: 3/8/2014 10:07:12 AM EDT by dead-bird]
Colt mags are available now.
There was a time "back in the day" you couldn't get them for any reasonable price.
Uzi mags were the only other game in town.
Link Posted: 3/8/2014 5:30:06 PM EDT
That was the situation when I first built this carbine back in 2004 or so.
Link Posted: 3/8/2014 5:47:33 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By dead-bird:
Colt mags are available now.
There was a time "back in the day" you couldn't get them for any reasonable price.
Uzi mags were the only other game in town.
View Quote
Metalform makes very nice mags. Brownells I heard is making their own, but may just be rebranding the Metalforms. The finish is different. Brownells also has a polymer mag.

I started with Uzi mags, but my gun wouldn't run. I then switched to Metalform, and also changed several other things. I never retested the Uzi mags after I got it running.
Link Posted: 3/8/2014 6:52:42 PM EDT
I haven't tried any new made magazines.
When the"Assault Weapons Ban" sunset, I managed to get enough Colt mags at Knob Creek to keep me happy.
In hindsight, I should have gotten more, a lot more...
Link Posted: 3/8/2014 8:39:54 PM EDT
No issues with my new ASC colt pattern mags bought last fall either. I too hear the Brownells mags are metalform. They can be had 3 for $93 too so thats a lot better deal than metalform. My ASC's were $16 per.
Link Posted: 3/9/2014 7:59:04 AM EDT
[Last Edit: 3/9/2014 10:19:36 AM EDT by heavyduty]
Probably a stupid question, but I haven't looked at 9mm AR systems in years and can't remember - my RRA barrel and BCG are considered Colt system, right? IIRC the other system was Oly's.

I should like read the FAQ, eh? Derp.
Link Posted: 3/9/2014 9:34:25 AM EDT
Oly's system is patented by Oly so I'm reasonably certain that you do not have an Oly system.

I think the Oly patent(s?) expire in a few years so when that happens, other companies may adopt the technology, hopefully at a lower cost and perhaps to other calibers besides those sold by Oly.

Not legal advice, MHO, YMMV, etc.
Link Posted: 3/9/2014 10:18:46 AM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By SecondAmend:
Oly's system is patented by Oly so I'm reasonably certain that you do not have an Oly system.

I think the Oly patent(s?) expire in a few years so when that happens, other companies may adopt the technology, hopefully at a lower cost and perhaps to other calibers besides those sold by Oly.

Not legal advice, MHO, YMMV, etc.
View Quote


Right - I know that it's not an Oly pattern, what I was asking for was confirmation my RRA stuff was Colt pattern.

And I could have answered my own question if I had looked at the pinned FAQ first.
Link Posted: 3/10/2014 4:50:20 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By heavyduty:
It's not a huge deal if I have to move over to Colt pattern mags, I really do want LRBHO.
View Quote

You're not going to be breaking any bolt catches with no LRBHO.

I've been using the Hy-Tech block for several years as well. I can use the same unmodified mags that I use in my Uzi... which also doesn't have a LRBHO feature.
Link Posted: 3/11/2014 6:28:13 AM EDT
I'm a big fan of the VMH block, too. Needs a little work with a file for total mag compatibility, but I like sharing mags with my Uzi.
Link Posted: 5/5/2014 5:56:10 AM EDT
[Last Edit: 5/5/2014 6:03:37 AM EDT by heavyduty]
OK, I think I'm ready to do this.

I want to order three mags with the Hahn dedicated mag block. How are the Brownell's magazines? Also, ASC has a 20 rounder that is appealing - are they any good?

Both the Brownell's and the ASC mags support LRBHO, right?

Any other parts I need to move from my VM system to Hahn?
Link Posted: 5/5/2014 10:55:27 AM EDT
I used the hahn dedicated block in mine and it worked well with colt or modified uzi mags. no complaints on the hahn.
Link Posted: 5/5/2014 11:34:32 AM EDT
Hahn dedicated block and 3 ASC mags ordered!
Link Posted: 5/8/2014 6:20:33 AM EDT
My Hahn dedicated block and ASC magazines arrived yesterday. I had to do some fitting to my lower (one of the first run NDS blems with the tight magwells) but the block is in and secured. Nice component!

I found a thread by strat81 in the archives about how to tune ASC mags for reliability with the Hahn dedicated block: C Products - ASC 9mm Magazine Function Write-Up This was a big help, I ended up doing everything he mentioned except for the mag catch notch fitting. Now all three reliably give me manual LRBHO; I want to manually cycle some dummy rounds through it once I find the ^@%^# bag of the things (I put them someplace really safe.)

I'm having a problem with my mag catch, it's not projecting far enough into the magwell for good retention of the 9mm mags. I'm looking at a fix for this common problem now.

I think my next steps are a set of BAD-EPS pins and a BAD-ASS selector, and bolt ramping plus a new FCG (ALG, maybe?) This is turning into a complete midlife rebuild!
Link Posted: 5/8/2014 6:37:07 AM EDT
Can you get one more turn out of the mag catch? That should help get more of the catch in the direction of the mag and might make a difference.

A ramped bolt is nice too.
Link Posted: 5/8/2014 9:43:37 AM EDT
Keep us posted. I'm in the process of putting together a 9mm. I've decided on the Hahn dedicated. But fine tuning is where I'm trying to really pay attention and see what others are experiencing or have experienced.
Link Posted: 5/8/2014 3:11:08 PM EDT
I recently out together a 9mm "Franken-pistol" using some parts I had laying around with a GM 10.5" barrel and pro-mag block, and CMMG ramped bolt. 500 rounds and not a single hiccup. Also required no "fine tuning". Point that I'm trying to make is that not all 9mm AR platforms are going to require the fine tuning. My opinion, find what you think you'll like and give it a shot, no pun intended.
Link Posted: 5/8/2014 7:16:17 PM EDT
My VM ran 100% for ten years!

I read up on the mag catch issue and ordered one of the RRA 9mm ones today.
Link Posted: 5/9/2014 6:17:46 AM EDT
I just tried a WECSOG diagnosis - a piece of electrical tape inside the mag well opposite of the mag catch as a shim. It completely resolved the retention issue with two of the three mags, so I'm thinking the new catch will fix things. The ASC mags are a decent fit in the Hahn block, and the tape removes all wiggle - almost too tight, so I think the mag to well fit is fine.
Link Posted: 5/10/2014 6:25:14 AM EDT
OK, next steps. Almost done with the rebuild, very happy with how it's going so far.

I have BAD's pivot and takedown pins and a BAD-ASS on order, they should resolve at least part of my tight upper issue and make the selector more usable. (I have BAD-ASSes on most of my ARs, this one never got one because the 9mm shortage kept it in the safe for over a year.) I also have another ALG QMS coming in.

Now, bolt ramping. My bolt is a RRA; who is currently doing ramping? ADCO and who else? Anyone here?
Link Posted: 5/10/2014 3:42:47 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By heavyduty:
Now, bolt ramping. My bolt is a RRA; who is currently doing ramping? ADCO and who else? Anyone here?
View Quote


IL,, ADCO Firearms is closest for shipping and turn around...
Link Posted: 5/15/2014 5:54:28 AM EDT
OK, ADCO it is - off it goes.

Once the bolt is back, the last thing I want to do is change out the CH with a GF or similar. The ALG FCG is in along with the BAD selector and pins. Almost done!
Link Posted: 6/13/2014 8:21:51 PM EDT
It's finally done - ramped, new FCG, new CH, Hahn block, everything. I had to wait for RRA's glacial shipping to get a new mag catch, my old one was dropping mags and RRA was the only 9mm optimized one I could find. I'm hitting the range in the morning with 200 rounds.
Link Posted: 6/14/2014 4:08:49 PM EDT
Range report: 100% function with 100 rounds of WWB and 100 of Federal bulk. The tuned C Products 32 rounders worked perfectly. I'm happy as shit with how this turned out!
Link Posted: 6/17/2014 12:05:41 PM EDT
Since the topic is mostly the Hahn block, I have to ask:
All this tape and adjusting - is it just a Hahn issue? My RRA block dropped right in and functions perfectly with uzi and Cprod mags. But I'm new to 9mm ARs, and wanna know what could happen in the future or on future builds.
Link Posted: 6/17/2014 7:38:04 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By N4cer:
Since the topic is mostly the Hahn block, I have to ask:
All this tape and adjusting - is it just a Hahn issue? My RRA block dropped right in and functions perfectly with uzi and Cprod mags. But I'm new to 9mm ARs, and wanna know what could happen in the future or on future builds.
View Quote


Nope, it was just a workaround for a bad mag catch, noting to do with the Hahn block. I replaced it with a RRA 9mm specific catch and everything works fine now with no tape.
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