AR9 Help

[M36]

I bought an AR9 upper at a gun show with all the assurances that it was fine. When I tried to shoot it with the Endomag inserts in a Pmag, the round would bury itself in the top of the chamber and not completely feed. This resulted in a "smile" like mark on the brass case and the bullet being pushed out of place in the case. The barrel is the ramped barrel in the pictures. I bought another non ramped barrel and it did the same thing. When watching the bolt push the round forward, I noticed that the bullet would take a deep dive in the primer area, and would then create a steep angle and would try to enter the chamber at the angle. I don't know if this was a mag issue or the bolt. You can see on the non ramped barrel the brass coloring and there would be the brass coloring on the ramped barrel also.

Since I could not figure this out I began to suspect the bolt area that strips the round from the mag and pushed it forward. To me it didn't feel very smooth and was binding up with the case not allowing the case to slide up under the extractor. I tried to polish and smooth down that area and got to a point where steel 115 gr rounds will feed, but brass cases with not. The steel feeds into the non ramped barrel but since I havn't played with this in awhile I am pretty sure it was still not feeding right in the ramped barrel. And I have tried several Pmags with the Endomag inserts. I would rather use the ramped barrel but ideally I would like this working in both.

The pictures are not very good. Anyone have any ideas?

BTW The buffer and recoil spring have been changed to accommodate the 9mm and I could not get clear pictures of the bolt area I was talking about.

 

[M36]

Just watched a video and had the same problem the guy in the video had. I believe the rear of the case is getting caught on two corners of the bolt part that pushes the round forward and created the two shiny marks on the case. Prob explains why the steel rounds wouldn't work. I thin if I can smooth the corners causing this it should be good.

 

[TonyTheTiger]

I would try the same upper on a dedicated PCC lower. $1.47 says it runs perfect.

 

[Bluedog82]

Agreed, sounds like it’s mostly a magazine related issue…buy a proper lower or at least a magwell adapter that lets you run pistol mags

 

[CK1.0]

Those Endo-Mags seem like a great idea… probably works 100% in at least 2 or 3 guns out there. Everyone else should probably just get a lower that takes Glock mags lol.

 

[bfoosh006]

Just watched a video and had the same problem the guy in the video had. I believe the rear of the case is getting caught on two corners of the bolt part that pushes the round forward and created the two shiny marks on the case. Prob explains why the steel rounds wouldn't work. I thin if I can smooth the corners causing this it should be go

From the looks of the ammo... it looks like you have some "sharp" edges that could be smoothed.

The chamber, edge at the top of the ramp ( the radius into the chamber ) , and the face of the bolt. You might try Polishing those surfaces ... Do NOT GRIND on the surfaces

As you can see.. those spots are sharp enough to grab the bullet and case.

Can you also post some pics of the bolt face and edge you might polish ?

I'm not a fan of feed ramps that leave some of a 9MM AR chamber unsupported. It is pretty easy to have a blow out at that spot if the ramp is over done.

Do you have photos of some fired brass ? ... looking for "Glock" bulge at the rim end ?

As you mentioned... the upper is going to be dubious in QC. Combine that with EndoMags, and it might never function great.

If you can find some Remington UMC 115gr you might try that as well... before the Remington issues, that ammo was the shortest OAL I have ever seen in bulk 9MM. Not sure if the restructured Remington still makes it like that.

 

[rpoL98]

look at the brass, copper witness marks on the top, bottom, where ever, on your barrel feed cone, feed ramp. it's practically telling you where you need to smooth out the sharp edges, deburr, and polish. sometimes it helps to take a pic with a hi-rez camera, up-load the pic, and then view it on a 40" monitor. hard to miss the clues when they're that big, staring you in the face.