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Nordschleife
07-17-2007, 8:39 AM
Well I posted a thread regarding a problem I was having with my 9mm AR last week. Every other shot caused a jam and I had no idea what was going on. I thought it was the mag-block, but it wasn't, then I tried using different magazines, but nothing either...kept jamming. Then my friend had a look at it and we discovered that the bolt is hitting the hammer as it's sliding forward into the chamber...it's getting stuck halfway through.

Has anyone experienced this? We had no idea how/why it was doing this..but the upper is fine. I used two other lower assemblies on my RRA upper and it shot great; the problem lies with my own lower assembly.

Perhaps ramping the bolt may solve this? I ordered a new hammer from RRA. Hopefully this fixes it, but if not; time to hit up a shop.

ar15barrels
07-17-2007, 9:08 AM
Well I posted a thread regarding a problem I was having with my 9mm AR last week. Every other shot caused a jam and I had no idea what was going on. I thought it was the mag-block, but it wasn't, then I tried using different magazines, but nothing either...kept jamming. Then my friend had a look at it and we discovered that the bolt is hitting the hammer as it's sliding forward into the chamber...it's getting stuck halfway through.

Has anyone experienced this? We had no idea how/why it was doing this..but the upper is fine. I used two other lower assemblies on my RRA upper and it shot great; the problem lies with my own lower assembly.

Perhaps ramping the bolt may solve this? I ordered a new hammer from RRA. Hopefully this fixes it, but if not; time to hit up a shop.


What type of hammer do you have?
You need an un-notched hammer.
If you have a notch on it like the picture below, it's not going to work.

http://ar15barrels.com/tech/hammer-mod.jpg

Nordschleife
07-17-2007, 9:23 AM
What type of hammer do you have?
You need an un-notched hammer.
If you have a notch on it like the picture below, it's not going to work.

http://ar15barrels.com/tech/hammer-mod.jpg

I'm using a RRA hammer. It's not notched like that, it's a smooth bend around the top portion of the hammer.

REDHORSE
07-17-2007, 9:54 AM
• RRA & Colt 9mm hammer work with SOME .223 improved style AR15 bolt carriers. If your firing pin in your .223 bolt carrier is completely shrouded, then the 9mm hammer should also work with your .223 bolt carrier. If you have a .223 bolt carrier that you can see the the whole tail end of the firing pin (from looking at the bottom of the carrier), then the 9mm hammer will not work with your .223 bolt carrier group. You will have to switch back and fourth with the .223 & 9mm hammer then, when you covert from .223 & 9mm uppers.

9mm hammer vs the majority of the AR15 .223 hammers
http://www.ninthstage.com/wp-content/uploads/2006/03/Hammers%20S.jpg

• DPMS .223 hammer (http://www.dpmsinc.com/store/products/?prod=906) is compatible with both the 9mm bolt and .223 bolt carriers.

The DPMS .223 hammer differs from the majority of the other AR15 semi-auto hammers out there in the market. It more closely resembles the M16 hammer. It lacks the notch/cut out that most of the AR15 hammers (top front corner) have, that hangs up on the 9mm bolts.

http://img48.imageshack.us/img48/3549/dpmsar15hammerhd1.jpg

The other option is to have your 9mm bolt "Ramped", so that you can use standard AR15 hammers.


I have a 9mm hammer for my AR15. I use my 9mm upper along with my .223 upper, without swapping out hammers. My .223 bolt carrier, is of the enhanced type.

AJAX22
07-17-2007, 9:56 AM
The .223 enhanced bolt carrier is identical to the M16 bolt carrier at the firing pin isn't it?

Nordschleife
07-17-2007, 10:19 AM
The .223 enhanced bolt carrier is identical to the M16 bolt carrier at the firing pin isn't it?

I'm not completely sure, but I did read somewhere on a previous search that the enhanced bolt was nothing more than an M16 bolt carrier.

ar15barrels
07-17-2007, 11:48 AM
The .223 enhanced bolt carrier is identical to the M16 bolt carrier at the firing pin isn't it?

http://ar15barrels.com/tech/ar15carriers.jpg

superhondaz50
07-17-2007, 5:55 PM
Are you running a 9mm hammer or a dpms type hammer. The 9mm hammers can cath the bolt and make it jam

Nordschleife
07-18-2007, 8:25 AM
Are you running a 9mm hammer or a dpms type hammer. The 9mm hammers can cath the bolt and make it jam

I'm running a 9mm Rock River hammer. It's confounding because I have three other friends with the exact same parts list and their rifles are running flawlessly. I suppose I may have installed something wrong, but I can't find out what it is, especially b/c we lined up all our lower receivers side by side and after careful analyzing, we could not find anything mis-matched or incorrectly placed.

I just ordered a new hammer from Rock River. I'm going to install it and see whether or not it helps.

superhondaz50
07-18-2007, 8:57 AM
ok, I know whats hppening. There is a small notch halfway down your 9mm hammer, this was put there to prevent slam fires (or someone removing the disconnector to try an FA there gun) whats happening is either the trigger is not catching the hammer, or the disconector is not working properly. the hammer is following the bolt as it closes and that little notch cathes the lip of the bolt, resulting in a bolt/hammer lock up. check out your disconector and make sures it works correctly.

Nordschleife
07-18-2007, 9:18 AM
ok, I know whats hppening. There is a small notch halfway down your 9mm hammer, this was put there to prevent slam fires (or someone removing the disconnector to try an FA there gun) whats happening is either the trigger is not catching the hammer, or the disconector is not working properly. the hammer is following the bolt as it closes and that little notch cathes the lip of the bolt, resulting in a bolt/hammer lock up. check out your disconector and make sures it works correctly.

Oh man, I can just picture what you said and it can definitely be a possibility. That's the first thing I'm going to do when I get back to the house- I'm going to disassemble those parts and have a thorough look at it. Thanks a lot for the tips.

Nordschleife
07-18-2007, 10:23 PM
I think I found the problem...and I feel like an idiot; I disassembled everything and I discovered that the connector spring was missing. I rummage around my tool box and after 20 minutes, I see a small spring right next to my punch kit.

Superhonda and everyone else, thanks a lot for helping me narrow it down. I'm going to hit up the range tomorrow and test the rifle out. I'll let you know how everything goes.

shootm
07-18-2007, 11:02 PM
The other option is to have your 9mm bolt "Ramped", so that you can use standard AR15 hammers.

You don't Ramp the Bolt. You Ramp the Carrier. :rolleyes:

ar15barrels
07-19-2007, 12:15 AM
You don't Ramp the Bolt. You Ramp the Carrier. :rolleyes:


9mm AR's don't HAVE a carrier.
They run in blow-back operation mode.
The bolt is one piece and slides in the upper receiver just like a carrier does on a locked-breech AR type firearm.

9mm bolt:

http://ar15barrels.com/tech/9mm-bolt.jpg

AR-15 bolt carriers:

http://ar15barrels.com/tech/ar15carriers.jpg

ar15barrels
07-19-2007, 12:18 AM
I disassembled everything and I discovered that the connector spring was missing.

Make sure you install it with the LARGE end of that spring down into the trigger so it snaps smartly into place.

Logic wants you to put in in backwards because it fits easier that way.
What happens is that the large end will get stuck down in the trigger for long enough for the gun to double ot triple, or just hammer-follow like it was doing for you without the spring.

Nordschleife
07-19-2007, 3:55 PM
Yep, I installed the larger end down onto the assembly first.

I figured the larger end of the spring should go in first since its diameter matched the diameter of the upper trigger's gap.

Just got back from the range, the rifle shoots excellent. This thing is really fun. Thanks for the help guys.