View Full Version : M1 Carbine slide malfunction - Need help!

May 3, 2012, 10:23 AM
I have an Iver Johnson M1 carbine .30 cal that I don't know much about.

When fired rapidly, the slide will partially come out of the grooved rails on the receiver and stick back. The person that gave me the rifle had already replaced the slide itself because someone told them that was the cause for the issue. However, the problem still persists.

Hopefully someone out there knows about these rifles and can provide me with some accurate information as to how to repair the issue.

I have included a picture to show what I believe appears to be the problem.(NOTE: The notches are at the TOP of the rail; the receiver in the picture is upside down) There are two little notches in the top of the slide rail on the receiver, near the back sight. The furthest notch towards the back appears to be a clean rounded half circle, while the notch a little further forward appears to be an elongated half circle (doesn't appear to be factory).

At any rate, the foremost notch is what allows the slide to get stuck back when fired, as it comes back and jumps partially out of the rail at that point and gets wedged into place. A firm forward bump on the slide shoves the slide back into place, but obviously this is not how the weapon should function.

Please let me know if the notches are supposed to be there, and if so, what for...if not, how did they likely get there? (Was it due to someone prying on the slide to disassemble it?) Just a thought, as it almost looks like the metal could be chipped.

Also, the the half circle notch at the back end of the rail, although it could be factory, doesn't make much sense because the slide doesn't ever come back that far.

What seems to be the cause for the slide issue?

ANY input will be appreciated!


May 3, 2012, 05:32 PM
You're wanting me to reach way back in my cloudy memory. Not sure but I think your IJ is one of the post war copies that came out--might be wrong. Anyway, on an original carbine there is supposed to be a notch toward the rear to allow for detaching the op arm from the bolt. Yours appears to be screwed up. If the op arm is disconnecting in operation the groove is probably worn out and the frame should be scrapped. Goat

May 3, 2012, 06:20 PM
After further inspection, it looks like the slide is not coming out of the notch, but because the top of the rail is ever so slightly crowned, it is allowing the slide to jump out and get wedged at that point. Also, the spring system has there always being pressure on the slide pushing it outwards...the combination of the the outward pressure of the slide from the spring mechanism, and the slightly crowned rail allowss the slide to come out of the rails.

I'm thinking about putting it in a vice to straighten out the crowning in the rail...the outward push of the slide from the spring seems to be just how the rifle is designed.

May 3, 2012, 06:41 PM
Can’t see any point in having an Iver Johnson
M1 carbine - no purpose
"You said ANY input":D

Sorry, couldn’t resist when I saw the note on the picture … just kidding …but I did have a Universal that broke a slide once.

Are you sure the slide is crawling over the rails, or is it just shifting into the notch and getting stuck at that point ?
Do you have a set of calipers?

If I remember correctly. The Universal I had did something similar and slicking up the rails fixed it (ONE of the times it broke). That gun was the only one I was happy to sell and never missed after it was gone.;)

May 3, 2012, 06:51 PM
OK, just posted and saw your second post … Is the slide actually coming out of the rails or binding when it cocks up ?

Bill DeShivs
May 3, 2012, 11:39 PM
Iver Johnsons were actually quite good carbines.

May 4, 2012, 08:06 AM
I’ve heard a lot of bad things about the Iver Johnsons, but never actually saw a lemon. Almost every Universal I ever saw was a lemon. Only had my paws on 4 or 5 IJs and 8 Universals. (Owned 2 of the Universals, and buddies had the rest.) To be fair, the IJ seemed much better.
I’ve kinda wondered if some of the bad rep for IJ came from the Universal.

James K
May 4, 2012, 11:26 AM
The front notch is for disassembly; it is where the op slide will come out to remove it. The rear "notch" is not part of the gun's operation, the slide doesn't even reach it. It is part of the machining for the op slide raceway. If you look you will see that the cut extends past it, but the op side raceway stops there. The narrow cut was done first, with an end mill, from near the lug seat back to within about an inch from the end of the receiver. Then a "T" shaped mill was put into that track, making that second hole, and moved down and forward (or rather the receiver, in a jig, was moved backward) to make the raceway cut at the bottom for the bottom lug on the op slide to move in.

So, yes, both those holes are there for a purpose.

Nice picture, though.

Now as to the op slide popping out. Have you checked for barrel alignment? That is often caused by a barrel that is not aligned properly, usually a replacement barrel. If the barrel is out of alignment, the tracks for the op slide will tend to twist the op slide and cause it to pop out, as well as producing excessive wear on the barrel, the slide and the receiver raceway.


May 4, 2012, 03:40 PM
LOL @ animal - yeah, I wouldn't haven't bought this rifle myself. It was given to me absolutely free of charge, so who's going to turn down a free rifle :D

I too have heard a lot of bad things about these, or at least things indicating that they are not the best rifles. With that said, that's part of the reason I haven't messed with it much...the .30 cal ammo is as much as .223, and I'd much rather dump money into the .223 ammo for another rifle.

I'll have to take another picture showind exactly whats happening.

Basically, I can pull the slide back and outward towards the right, and at the point in the rail where I said it was crowned, it will slip out of the rail and be wedged into place (its not quite as far back as the notches I originally thought was the issue).

May 4, 2012, 03:43 PM
also, does anyone know what a fair price to ask for this rifle in working condition would be?

James K
May 4, 2012, 09:45 PM
"I can pull the slide back and outward towards the right, and at the point in the rail where I said it was crowned, it will slip out of the rail and be wedged into place"

Yes, that is the way you remove the operating slide. Except you have to remove the operating spring and guide first, so the slide will disconnect from the guides in the barrel also.


May 5, 2012, 11:15 AM
Trying to remember stuff here …The Universal, (and maybe some Iver Johnsons?)

... use a different slide than the US Carbine and has 2 recoil springs/guides instead of one. The easiest way to tell by looking at the slide is at the point where it wraps over the top. In the military version, the guides for the bolt are "closed". The Universal version is an open stamped piece … and you can actually see the end of the bolt lug even when the gun is assembled.

Dunno if this helps, probably doesn’t … as I seem to remember the Iver Johnson having the "closed" style, and one of the things I liked about it vs. The Universal. The Universal I had that broke the slide, snapped off the top section of the bolt guide.:mad:
At some point, Iver Johnson bought out Universal. I dunno what style slide was used in the later Iver Johnsons/Universals. The crappy version of the slide may be unique to the Universal marked guns. …

James K
May 6, 2012, 10:12 PM
AFAIK, the IJ .30 caliber carbines were copies of the U.S. carbine and the functional parts are (or should be) intechangeable with the GI gun.


May 7, 2012, 06:42 PM
the tracks for the op slide will tend to twist the op slide and cause it to pop out

In other words, similar to the action I use when disassembling for cleaning?

I'm more thankful than I realized that most of the USGI examples have original barrels- that sounds like a problem that would make you tear your hair out