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1/22/2020 12:12:56 PM
Posted: 9/16/2007 2:13:38 PM EST
[Last Edit: 9/16/2007 2:14:02 PM EST by LonghornAR]
Howdy, all. I finished my 9mm SBR project for a while now but the build has been plagued with feeding and extraction issues every tine I've taken it to the range. I've held off posting here until I had tried enough magazines from different manufacturers to eliminate that as a possible culprit, but I think I'm admitting defeat and calling for the big guns in here for help.

First off, the build. RRA 7.5 9mm complete upper. DPMS lower with same LPK. RRA 9mm hammer and RRA 9mm buffer, tube, and spring. Hahn dedicated mag block. Promag and CProducts magazines.

The issues. With the Promag, I get failure to feeds. A single round is stripped from the magazine and is lodged diagonally between the bolt and the barrel. It's as if the case head doesn't caught by the extractor claw and then wedges itself between the bolt and barrel. With the CP, I get double feeds. Usually, the empty case is stacked on top of an unfired round. Some instances, the empty is stovepiped or even flipped backwards.

The other issues. Bolt hold open occurs randomly with both magazines. The percentage is higher with Promag but I've had it happen where it also doesn't lock back. If I manually apply force under the magazine with my hand and then cycle the action, the bolt does lock on both types.

To me, it seems like the mag block isn't high enough. Since it's the dedicated Hahn, I can't adjust its position in the mag well. I'm tempted to try a different mag block, but I'd like to hear from you guys first before I purchase another one. I don't want this to turn into a Hahn/RRA/DPMS bashfest because the quality of the components are good. I just think my combination of quality parts is skewed dimensionally somewhere and that's causing all my grief.
Link Posted: 9/17/2007 11:15:06 AM EST
As long as you keep them clean 9mms run pretty well with good hardware.

Promags are notorious lemons. Some work, some have been reworked, there have been several changes to them since they were introduced. At best they are flimsy plastic just waiting to break even if they do run. They make great chew toys if you have a dog, just take out the spring and small parts. CProducts are still working out the bugs in their new mags. They are coming out with a new follower here shorty and support their mags if you have any issues. They will probably be good mags once they get dialed in, time will tell. I am still waiting to see mags personally. Colt mags are the best mags you can get now. You may need new springs worst case scenario. They are expensive but I have Colt mags that are well over a decade old. Much cheaper than buying replacement crap over and over again. They currently have the best reputation.

Make sure the adapter's actuator that works the BHO moves freely. A couple drops of oil on the contact areas side and top to make sure it moves free and smooth. If it's stiff just work it up and down a bit and keep the area clean. The Hahn adapters were all optimized around the Colt mags and system. If mags or components are not at least up to that standard you may have sub par performance issues. Adjusting adapters and tweaks are really half assing solutions to other problems. The top of the adapter should be flush with the top of the receiver. If you have to move things to find a 'sweet' spot you have something wrong.

Your BHO spring may be too powerful. They can vary quite a bit from rifle to rifle. You want just enough spring behind your BHO to keep it in place, any more than that and it works against your magazine spring.

FTE is usually, if not always, a weak extractor problem. A weak extractor won't hold the case against the bolt for a hard hit against the ejector to knock it out The ejection system of a 9mm AR is just like a 1911 and troubleshoots the same. RRA bolts sometimes use a shitty roll pin to hold in the extractor, replace it with a split pin. You may have to bend your extractor to gain tension on the case rim. The hook of your extractor may also be poorly shaped but that is the least likely of possibilities.
Link Posted: 9/17/2007 2:47:48 PM EST
Thanks for the reply. It seems like I need to try out a genuine Colt mag before I start tweaking with the other components of the rifle. I'll go ahead and order one and see if that improves the performance. I've kept tabs on the CProducts thread regarding issues in Hahn dedicated blocks, but I'd like to make sure the problem is with the mags and not the rifle before I have them slicing up custom mags for me. No point in them spinning wheels as well - seems like they have their hands full already.
Link Posted: 9/17/2007 4:35:48 PM EST
[Last Edit: 9/17/2007 4:38:59 PM EST by Dehammer]
It seems they are having issues with the other adapters as well, according to the forums. The other adapters just aren't locked into one position and need to be 'adjusted' for CProducts mags. Problem is should you really need to adjust adapters between mags and what happens when an adapter gets out of adjustment? Not ideal.

I would get some Colt mags and hold on your CP mags until they get them dialed in. Hopefully they'll get the bugs (and that's all they really are) worked out sooner than later.
Link Posted: 9/17/2007 9:18:08 PM EST
i had to do some filiing on the front of the follower on my CP mags, no biggie, they all work 100% BHO and all
Link Posted: 10/3/2007 11:20:23 AM EST

Originally Posted By Dehammer:


FTE is usually, if not always, a weak extractor problem. A weak extractor won't hold the case against the bolt for a hard hit against the ejector to knock it out The ejection system of a 9mm AR is just like a 1911 and troubleshoots the same. RRA bolts sometimes use a shitty roll pin to hold in the extractor, replace it with a split pin. You may have to bend your extractor to gain tension on the case rim. The hook of your extractor may also be poorly shaped but that is the least likely of possibilities.


Where can I get one of these split pins?
Link Posted: 10/3/2007 4:16:10 PM EST

Originally Posted By Einstein:

Originally Posted By Dehammer:


FTE is usually, if not always, a weak extractor problem. A weak extractor won't hold the case against the bolt for a hard hit against the ejector to knock it out The ejection system of a 9mm AR is just like a 1911 and troubleshoots the same. RRA bolts sometimes use a shitty roll pin to hold in the extractor, replace it with a split pin. You may have to bend your extractor to gain tension on the case rim. The hook of your extractor may also be poorly shaped but that is the least likely of possibilities.


Where can I get one of these split pins?


LOWES, ACE, Home Depot, NAPA, TIFCO, WURTH, True Value, Tractor Supply, Harbor Freight, and possibly many more places.. 1/8 x 3/4 roll pin, at LOWES they is in the drawer marked "tension pin".

Mine is from Garrison, and the pin in the pic is what you is looking for -

Link Posted: 10/7/2007 8:58:33 AM EST
[Last Edit: 10/7/2007 12:13:19 PM EST by EltSrdkr]
height=8
Originally Posted By LonghornAR:
First off, the build. RRA 7.5 9mm complete upper. DPMS lower with same LPK. RRA 9mm hammer and RRA 9mm buffer, tube, and spring. Hahn dedicated mag block. Promag and CProducts magazines.

The issues. With the Promag, I get failure to feeds. A single round is stripped from the magazine and is lodged diagonally between the bolt and the barrel. It's as if the case head doesn't caught by the extractor claw and then wedges itself between the bolt and barrel. With the CP, I get double feeds. Usually, the empty case is stacked on top of an unfired round. Some instances, the empty is stovepiped or even flipped backwards.


I'm having the same problem with the case extraction. My setup is almost identical to yours

- RRA upper, hammer, and buffer
- Hanh mag block (mine is the precision bottom model)

I'll have to give the suggestion of bending the extractor and replacing the extractor roll pin. Were you able to resolve your issue? I looked at the extractor claw (or whatever it's called) on the mag block and it's just about flush with the top and side of the bolt carrier.

Here's a video of my problems:
www.youtube.com/watch?v=ueKBVh-y-zQ
When I clear the jam, the empty case drops out along with the fresh round that was ready to fire.

Very frustrating problem on a new carbine.

Link Posted: 10/7/2007 12:47:16 PM EST

Originally Posted By LonghornAR:
Howdy, all. I finished my 9mm SBR project for a while now but the build has been plagued with feeding and extraction issues every tine I've taken it to the range. I've held off posting here until I had tried enough magazines from different manufacturers to eliminate that as a possible culprit, but I think I'm admitting defeat and calling for the big guns in here for help.

First off, the build. RRA 7.5 9mm complete upper. DPMS lower with same LPK. RRA 9mm hammer and RRA 9mm buffer, tube, and spring. Hahn dedicated mag block. Promag and CProducts magazines.

The issues. With the Promag, I get failure to feeds. A single round is stripped from the magazine and is lodged diagonally between the bolt and the barrel. It's as if the case head doesn't caught by the extractor claw and then wedges itself between the bolt and barrel. With the CP, I get double feeds. Usually, the empty case is stacked on top of an unfired round. Some instances, the empty is stovepiped or even flipped backwards.

The other issues. Bolt hold open occurs randomly with both magazines. The percentage is higher with Promag but I've had it happen where it also doesn't lock back. If I manually apply force under the magazine with my hand and then cycle the action, the bolt does lock on both types.

To me, it seems like the mag block isn't high enough. Since it's the dedicated Hahn, I can't adjust its position in the mag well. I'm tempted to try a different mag block, but I'd like to hear from you guys first before I purchase another one. I don't want this to turn into a Hahn/RRA/DPMS bashfest because the quality of the components are good. I just think my combination of quality parts is skewed dimensionally somewhere and that's causing all my grief.



hearing about all of the issues that people have with their mutt AR builds, im glad i bougth my OA K9. People can poo-poo OA all they want, but my K9 has worked 100% from day 1.

One thing my LGS told me about these 9mm ARs is that your mag should be snug in the magwell. If it ist you may have issues and he was speaking of Colt 9mm ARs too. before you do any major mods/tweaking, i would buy a Colt 9mm mag. Just one now and see how well that fits and functions in your gun. then you could go from there. BTW. when i put my Hahn mag block in my AR it didtn fit - too wide by a couple thou. Once i milled one face it fit fine. For the sten mags i bought, i put several layers of masking tape on the sides to make them snug in the mag well and did some testing. i did find that if the mag had alof of play, it would cause problems. It maynot be the same with your system, but im thinking alot of your issues are mag related.
Link Posted: 10/8/2007 4:44:31 PM EST

Originally Posted By edlmann:

Originally Posted By Dehammer:
RRA bolts sometimes use a shitty roll pin to hold in the extractor, replace it with a split pin.


I give up. What's the difference between a roll pin and a split pin?


The split pin is what is pictured above, a heavy piece of sheet metal curled end to end.

The roll pin that is problematic is made of thin sheet metal that looks like whats at the end of a key after opening a can of spam.
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