Kahr/Auto-Ord. 1927A-1 reliability

[johncantiusgarand]

I own a Kahr/Auto-Ord. 1927A-1 "Commando" model that has been giving me fits at the range. Accuracy is phenomenal, but it jams every fourth or fifth round (for me, at least; my son fired the first 30 rounds of the day flawlessly, but when I followed up with twenty it jammed like crazy). This was the second range trip with it, and the previous range session was similar--first magazine seemed to feed fine, but it started jamming thereafter. And I only have one magazine, so it isn't a "one of your magazines may be bad--keep the good one" issue. I'm usually able to scour the web for tweaking and tuning tips for my firearms, but the web information on the semi-auto "thompsons" is sketchy. People either love them or hate them. The haters, while admitting they have "cool factor" appeal, damn them as jam-o-matics and say that they need a lot of "work" to run reliably. Satisfied customers say that they feed everything given them. What information is lacking out there is exactly what "work" is entailed to make them feed reliably.

Mine fails to feed. The round ends up canted about 45 degrees to the right and wedged there by the bolt whose face now mangles the rim. I can usually withdraw the bolt slightly which frees the stuck round enough that when I release the bolt, the round then chambers. 4 or 5 rounds later, it happens again.

Some things I haven't had time to run to ground yet: we were both firing from a bench, and due to the length of the supplied 30 round stick magazine, the rifle ended up resting on the magazine base. I suppose that could have been a factor, but I remember it jamming on the first range trip as well when I was standing. I also have four G.I. magazines that I haven't tried, because I haven't modified their magazine catch hole yet. Perhaps the "factory" magazine (which is just a G.I. magazine Kahr modified already) is bad, and the G.I. magazines I have will work better.

But rather than try different mags or--"gasp"--return the rifle to the factory, I'd really like to know what is making mine jam that way. The feed "ramp" area is really more of a large, smooth funnel which, from the looks of it, would seem to defy jamming.

Anyone with hands-on experience tweaking these things?

 

[rcmodel]

And I only have one magazine, so it isn't a "one of your magazines may be bad--keep the good one" issue.

Like it or not, that's what it sounds like to me.

You could try some feed-lip tweeking on your one mag, but you really need to try another mag or more, to pin it down and rule out a gun problem all together.

You also didn't mention what kind of ammo you are using.
Have you tried anything else?

rcmodel

 

[johncantiusgarand]

Yeah, I forgot to mention the ammo; sorry about that. On the first range session we used WWB 230 Grn Ball. This last trip we also used "value pack" ammo, but it was Remington UMC 230 Grn. Ball. I've heard complaints about the bulk stuff from Wal-mart before, but we were also shooting two of my Colt 1911's, and they gave us no trouble.

I am going to modify the G.I. magazines today, but I don't know when I'll get to the range again. As for tweaking the other magazine feed lips, I just have no idea what to shoot for. Do you suppose that it is releasing the round too early? Late?

 

[rcmodel]

Well, I must confess I have never even looked at a Kahr Thompson, let alone worked on one. And it has been at least 45 years since I had a real Thompson apart.

I would suggest you take out the recoil spring so you can carefully & slowly hand cycle the action.

Watch for what is happening to the round as the bolt pushes it out of the mag and go from there.

rcmodel

 

[johncantiusgarand]

I tried your suggestion today. Before I started, I noticed that the line that marks the transition from the widened rear portion of the feed "funnel" to the narrow front portion had a lot of brass and copper rubbed off on it. Only the left side showed this rubbing; the right side was clean.

With the guts removed from the upper receiver, I looked down the barrel with a loaded magazine installed. If the top round was on the left (the firearm's left--that is), I could see less of it than if it were on the right. Either the machining of the magazine seat was slightly off-center, or the magazine itself was a little wee-wad. I then reinstalled the bolt only and, per your suggestion, slowly chambered a rounds from the magazine. Top left rounds contacted that transition area every time. Top right rounds were much more of a straight shot into the chamber.

Next, I modified the magazine holes of my four G.I. magazines so they would fit and and tried it with them. The difference between the top left and top right rounds was much less pronounced with the G.I. magazines, so it looks more like the factory mag was just off some.

I surmise that a round feeding from the top left was prone to glance off that feeding funnel transition area hard enough to wedge the nose against the extractor clearance cut on the upper right side of the funnel. Even if the cause for its contacting that area seems to be magazine-related, it bothered me that a bullet nose contacting that area could be so disastrous. In an attempt to lessen the odds of that happening, I have blended that area slightly with needle file and stone and removed some burrs from the extractor clearance cut. I'll post a range report after I test fire it. But hopefully the better fit of the G.I. mags combined with my smoothing will have solved the problem. Thanks for your advice. Sorry, no pics yet of my work, but here is a pic of the brass and copper transfer on that feeding funnel transition line.