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Posted: 6/29/2025 4:27:01 PM EDT
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So last year I inherited a Plainfield M1 Carbine. From what I understand, those are considered some of the better commercial M1 copies. And it generally seems to do just fine. One oddity I have noticed is if I lock the bolt open and insert a loaded magazine, then run the bolt to chamber, I usually get a malfunction. Looking at things, the bolt doesn’t lock back quite far enough to clear the rear of the cartridge. This causes the topmost cartridge to pop up a little, causing the malfunction. I realize I can just insert the mag with the bolt forward and load the chamber normally, and that is what I do. It’s literally the same series of motions. But is this type of failure normal? Or did I just get a “special” one? 
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Does it do this with a different mag? 20 or 30 rounder? I see some different types of ammo in the picture. Does it do it with factory ammo? Are you pulling the charging handle completely to the rear then letting it go? |
3-7-77
Proud Member of the Leather Head Mafia
“In my opinion, the M1 Rifle is the greatest battle implement ever devised” - George S. Patton
Proud Member of the Leather Head Mafia
“In my opinion, the M1 Rifle is the greatest battle implement ever devised” - George S. Patton
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It's done it with all of the mags I've tried it with. KCI (15 & 30 round), Keep Shooting (15 round), and the one unknown mag (15 round) that came with the gun. Ammo in the picture is all the same. 110 gr. PPU JSP, in this instance. Just a trick of the lighting that makes the lower cartridges look different. But ammo doesn't seem to make a difference. It has done this with both commercial ammo and reloads. And yes, the charging handle is pulled all the way to the rear to chamber the round, but that's not the issue. Inserting the loaded mag with the bolt locked back causes this issue. So when I pull the charging handle to the rear, the top round is already popped half way out of the mag. Based on your questions, I assume this is not typical. I suspect the issue being the slot for the bolt catch was milled just a little too far forward. If the bolt were to lock 1/8" farther to the rear, this condition would not happen. |
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Mag's probably seating a bit too high when the bolt is locked back. My Iver-Johnson M1 Carbine does the same exact thing if the bolt is locked back and I seat a mag. I seat a mag with the bolt closed and zero failures to load. |
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Originally Posted By myitinaw: @DonFlynn Your M1 Carbine wizard level of advice is needed.  HUH? I'm not going to be much help here, my Plainfield M1 carbine is a tad mag picky also. Off the top of my head I would try FMJ 1st instead of the soft tips. Other than that it could need a new mag catch and spring. I haven't had the time to trouble mine (a friend wants it and I won't sell it until I think its reliable). Mine is stovepiping every few rounds. I'm thinking rebuilding the bolt but just haven't taken the time to do that. |
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Originally Posted By DonFlynn: HUH? I'm not going to be much help here, my Plainfield M1 carbine is a tad mag picky also. Off the top of my head I would try FMJ 1st instead of the soft tips. Other than that it could need a new mag catch and spring. I haven't had the time to trouble mine (a friend wants it and I won't sell it until I think its reliable). Mine is stovepiping every few rounds. I'm thinking rebuilding the bolt but just haven't taken the time to do that. Originally Posted By DonFlynn: Originally Posted By myitinaw: @DonFlynn Your M1 Carbine wizard level of advice is needed. HUH? I'm not going to be much help here, my Plainfield M1 carbine is a tad mag picky also. Off the top of my head I would try FMJ 1st instead of the soft tips. Other than that it could need a new mag catch and spring. I haven't had the time to trouble mine (a friend wants it and I won't sell it until I think its reliable). Mine is stovepiping every few rounds. I'm thinking rebuilding the bolt but just haven't taken the time to do that. I think you are on the right path with this. Try FMJ ammo, different mags, mag catch and take the gun apart to check springs. Lube it and try it again. |
3-7-77
Proud Member of the Leather Head Mafia
“In my opinion, the M1 Rifle is the greatest battle implement ever devised” - George S. Patton
Proud Member of the Leather Head Mafia
“In my opinion, the M1 Rifle is the greatest battle implement ever devised” - George S. Patton
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It looks like your bolt "lock back" position is to far forwards compared to my M2 Plainfield. (this could be because of your slide or the notch is not correctly machined position wise) As such it is messing with the setting of the round in the magazine and when you cycle it, it is messed up to begin with and won't work If you look at the picture, the bolt is further back (less bolt is showing) and it completely clears the magazine and ammo when locked back. When you "seat" a magazine, the bolt should NOT touch any of the magazine or ammo.  " />
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Originally Posted By tooldforthis: It looks like your bolt "lock back" position is to far forwards compared to my M2 Plainfield. (this could be because of your slide or the notch is not correctly machined position wise) As such it is messing with the setting of the round in the magazine and when you cycle it, it is messed up to begin with and won't work Thank you for validating what appears to be the apparent cause. When I get a minute I’ll see if there’s a good place to take some measurements to compare. That should make it obvious if this is the culprit or not. |
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Even on most of the USGI M1 Carbines I have had, the lock back feature has been iffy. I think the little pin sitting in the little hole design is too shabby once any kind of wear develops, and since there is some wobble to charging handle. Because of that, I don't recall even attempting to load from a locked bolt. The only time I have used the feature is when the range officer wants to see the magazine removed and the bolt locked to the rear when he calls range cold. And now that I think about it, I'm pretty sure I just normally throw the safety flag in it instead of messing with trying to lock it back and hope it stays locked in the open position. Unless you buy some of the magazines with hold open feature, the rifle wasn't even designed to hold open upon firing on last round. Even then, the bolt is just getting hung up on the follower, so as soon as you rip it out, the bolt goes home again. I guess what I am trying to say is, don't load it that way and you won't have a problem. Even if the feature allowed you load the magazine without malfunction, you still have to manually pull back and release the charging handle because there is no bolt release paddle or button on the gun. |
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"you still have to manually pull back and release the charging handle because there is no bolt release paddle or button on the gun. " pretty sure we are all aware of this, not many who own a carbine are still looking for the bolt release paddle. He asked a specific question about WHY the gun was doing what it was doing |
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Originally Posted By tooldforthis: "you still have to manually pull back and release the charging handle because there is no bolt release paddle or button on the gun. " pretty sure we are all aware of this, not many who own a carbine are still looking for the bolt release paddle. He asked a specific question about WHY the gun was doing what it was doing And I gave him the answer. The gun was not designed to operate that way, so there is no reason to do it that way, so there is no malfunction. |
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