HELP request - 45acp pistol caliber carbine jamming "nose up"

[Heavymetal45]

Anyone else ever had similar issues. I recently finished putting together a new ar45 and can' get more than 2 rounds to chamber consistently. After looking at the bolt face I am wondering if it isn' because of the large block at the bottom. There is no way for the base to slide up in the rear and their is no feed ramp, I'm kinda wondering how it was ever supposed to work.

 

[Schroeder0278]

I built the same kind of gun. New Frontier Armory AR45 upper, lower, BCG, and a Kaw Valley 8 1/2” barrel. The BCG is milled out for the ejector on one side but the face of the bolt on the other side has a sharp edge at the 7-8 o’clock position. Once that edge is removed the gun will cycle properly. Here is a photo of how my gun was jamming.

So I’m in the same situation with my ar45. New Frontier BCG and Kaw Valley 8.5” barrel. You seem to be pretty confident about this fix and I was hoping you could provide a picture of the fixed bolt as reference before I start filing. The picture attached is the edge I believe you’re talking about.

 

[Fj40klr]

So I’m in the same situation with my ar45. New Frontier BCG and Kaw Valley 8.5” barrel. You seem to be pretty confident about this fix and I was hoping you could provide a picture of the fixed bolt as reference before I start filing. The picture attached is the edge I believe you’re talking about.

That’s the correct edge that needs to be filed down.

 

[Schroeder0278]

View attachment 35767


That’s the correct edge that needs to be filed down.

Thanks for the prompt response! I’ll update later with results.

 

[Jellybeanbaked]

I built the same kind of gun. New Frontier Armory AR45 upper, lower, BCG, and a Kaw Valley 8 1/2” barrel. The BCG is milled out for the ejector on one side but the face of the bolt on the other side has a sharp edge at the 7-8 o’clock position. Once that edge is removed the gun will cycle properly. Here is a photo of how my gun was jamming.

How did you remove that sharp edge? With dremil?

 

[Jellybeanbaked]

Thanks for the prompt response! I’ll update later with results.

Did that take care of your feeding issues?....i think im in the same boat

 

[Schroeder0278]

Did that take care of your feeding issues?....i think im in the same boat

Yes it definitely helped. I just used a file and smoothed it out and instead of getting malfunctions ever few rounds I might get one out of 50 rounds. I’m not sure if I took off enough material but the significant improvement makes it enjoyable enough to shoot that I haven’t cared.

 

[Jellybeanbaked]

Yes it definitely helped. I just used a file and smoothed it out and instead of getting malfunctions ever few rounds I might get one out of 50 rounds. I’m not sure if I took off enough material but the significant improvement makes it enjoyable enough to shoot that I haven’t cared.

I worked on it today but still jamming a lot like every other round......maybe i didnt file it down enough

Also wondering if i should do some polishing on the barrel

 

[Jellybeanbaked]

I worked on it today but still jamming a lot like every other round......maybe i didnt file it down enough

Also wondering if i should do some polishing on the barrel

Im useing a FM 45 bolt with a joeboboutfitters spartan glock lower and upper with 4 inch kak barrel

 

[Phazer]

It's been awhile, but I've never given up on searching for a solution.

When the owner brings the carbine back for me to look at, I want to try what Schroeder0278 recommended.

I also found this video describing the problem:

 

[technicalgadget]

If your not returning the barrel, might increase the amount of chamfer on the lower edge of that barrel. You can see how it's discolored there from scraping up against the copper jacketing of the round. Increasing the chamfer and polishing out the bottom edge of that will probably help.

 

[4WHLDRFTN]

check the extractor tension ... doesn't look like the case is sliding under it

 

[Phazer]

check the extractor tension ... doesn't look like the case is sliding under it

Agreed.

The last video posted was by a guy who found exactly what you said. He described how he fixed the issue.

 

[Phazer]

After more time passed, and more videos were reviewed, it appears that other users had problems with chambering rounds because of interference from the lower lug (or lip) on the inferior rim of the bolt face. This lug prevents rounds from sliding under the extractor and seating flush on the bolt face. This results in rounds being pushed towards the chamber at too steep of an angle with a subsequent jam (as illustrated in the original post from years ago).

Here is the original, unmodified, bolt face:



After some work last November, here is the modified bolt face after reducing the inferior lug:









Since the modification, round chambering and carbine function has been completely reliable.

According to the carbine's owner, he is happy not to have a paperweight in his safe any longer. He frequently takes the .45ACP carbine with its 9mm sibling to his outdoor range and really enjoys shooting them.