M1C - Gas Piston Nut

[ppknut]

While doing a rather complete cleaning of my M1C, I noticed that the Gas piston nut was a little loose. It could jiggle a bit while wiping this area down.

I've never tried to remove the gas piston and hadn't noticed this before.

It this "looseness" normal or should the nut be tight?

Thanks for any input.

-ppknut

Information

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[Col. Colt]

M1 Carbines have the piston nut retained by staking - no, it should not move. I would suggest getting the US Ordnance Maintenance manual, or at least looking it up on line, for details, and you will need a piston nut wrench to tighten it, before re-staking. While ordering the wrench, you may want to also pickup a trigger spring tool, and if finances allow, the bolt take down tool. These last two are optional, but the tasks they address are otherwise pretty difficult to do without them. CC

PS - "M1C" is a bit of an awkward abbreviation for "M1 Carbine", since there is an Official "M1C" (Garand) Sniper rifle. We know what you mean on the Carbine forum, but elsewhere it will confuse people!

[Bruce McAskill]

Check to see if your piston is staked in place and the nut is only moving a little bit. If this is the case then don't worry about it as it will function fine. But if the nut is very loose then it has to be tightened. Just be sure not to over tighten it as you can crack the cylinder.

[ppknut]

Thanks for both replies.

I have the Ordnance Field Service Technical Bulletin 23-7-1. I also have Ruth & Duff's Guide. The Tech Bulletin does not seem to mention the piston being staked. R & D mention that it is staked, but do not describe or show where the stake is, or how to remove it. The nut only wiggles back and forth a little less than a mm and seems to stop at either extreme of the travel directions.

I see no obvious pin or stake on the exterior of the piston housing, just the port on the bottom. Both manuals mention having the tool to remove the piston nut, but neither mentions how to remove a stake/pin I cannot see nor find.

I will be trying to find the nut wrench as well as the bolt take down tool and trigger spring tool (any idea who to buy these from?). But it'd be nice to know more about the staking issue. I certainly don't want to use any force with the nut wrench if there is a stake that needs removal first.

---------- Post added at 02:49 PM ---------- Previous post was at 02:46 PM ----------

p.s., I never thought about the MIC Garand! In all my paperwork, I just abbreviate M1 Carbine as M1C for my own convenience.

[CrossedCannons]

Staking refers to deforming the metal between mating surfaces of two parts (by impact of chisel, pointed tool, or "stake") to prevent their relative motion. There's no pin or "stake" to be removed.

Look at your rear sight, how it's held in the dovetail - see the chisel marks? That deformation locks the sight in place. Same technique used around the pin hole to hold the pin in the front site.

[DaveHH]

I would also consider obtaining a new gas nut before doing anything further. They staked them during the war as an expedient when plenty of depot parts were available. Staking is a deformation of both nut and cylinder threads as in smash and bend. A deformed nut thread can wreck a gas cylinder thread when it is cinched down. Better to remove the old one, and slowly put in a new plug which will act like a tap in the female threads. Run it down snug, back it out and put a drop of loktite or permatex and it will be fine. Remember that most nuts I've seen were not completely into the cylinder sometime quite a few threads were still exposed outside. As Bruce says, don't overtighten it as a cracked cylinder is fatal. Also if the nut shakes a bit but is still firmly locked by the staking and the carbine works, it is a non-problem.

[ppknut]

A little education goes a long way! Thanks for clarfying the staking issue. I now understand what's going on. The nut is staked so it can't back out, but it has a little play, which allows the wiggle. Thanks. At this point, in answer to my original question, "Is this normal?? it would appear that it is just that. I will, nonetheless, keep an eye on it, but I see no reason to remove it at this point in time.

I believe I will pursue the additional tools. Any reasonable source for these? I'll probably check the usual sources like Brownells, but if there is a better place, let me know

Thanks again to all

-ppknut

[CrossedCannons]

Sometimes these nuts require considerable torque to remove, sometimes not, depending upon how badly the threads have been "mashed" and how much crud has accumulated during use. When you get the wrench (very common $10 item), be sure its 3 lugs are not rounded off (if used) and that you apply firm (!!!) pressure of the wrench into the nut while unscrewing it so as not to round off the nut's mating lugs. Holding the barrel in a vise is helpful if you don't have 3 hands. If you do fubar the nut, you will make your removal job 10X harder. When reinstalling a new nut, it is very easy to crossthread it trying to screw it in so be careful. I'm sure there was a reason this wrench was not issued to the individual with the carbine.