Stuck gas piston on M1 carbine

wileybelch · July 31, 2013, 06:24 AM

How loose is the gas piston on the M1 Carbine supposed to be? I want to give my Carbine a thorough cleaning and the piston seems to be stuck as it won't budge after removing the retaining nut. Is there a safe/proper method for removal and subsequent cleaning?

**4V50 Gary** · July 31, 2013, 08:09 AM

Kroil. Soak it for twenty-four hours.

Dixie Gunsmithing · July 31, 2013, 08:38 AM

Kroil or any other penetrating fluid. What I do is use modelers clay, and build a dam around the piece stuck (leaving access to the stuck joint), forming a cup to hold a small amount of fluid in, which then soaks in over night.

James K · July 31, 2013, 09:26 PM

Wrap the jaws of pliers with copper or even friction tape and twist and pull it out.

Jim

wileybelch · August 1, 2013, 04:39 AM

Thanks, guys. While waiting for your replies, I soaked the piston with diesel fuel (rifle vertical to hold the solvent, I didn't have any Kroil) overnight. This morning I could rotate the piston but not pull it out (easily). Since there is so little gripping room on the piston, I tried to grab the end of the piston with the mouth of an empty .308 Win case which (after tapping lightly) nicely gripped the piston so I could rotate it and eventually wobble the piston out of the gas block. Sure enough, there was the usual black carbon fouling around the piston but it was now soft and easily wiped clean. What do you recommend for cleaning the inside of the gas block and how do you leave it after cleaning? Dry, lubed? What? Also, instead of peening the lock nut after reassembly, can a drop of LocTite 242 be used?

Grump · August 1, 2013, 10:52 AM

Re-assemble the piston dry.

Threads? READ the temp specs on that Loc-tite 242 and then consider that normal firing rates raise the temp of the barrel and pistol above boiling. I'd want something that works above 350° F. and preferably to 450 or so.

Metal always holds up, until reachuing the temps where it starts to lose temper. Beyond the scope of expected use, and even high-temp Loc-tite will melt or burn by then. I believe that most (if not all) will FIRST melt and stop locking before they burn and totally glue crap together.

Peened metal is unlikely to "glue" itself together too badly, especially if some quality lube is used on the threads (no rust allowed). Obscure cold-weld and cold-solder concerns don't really apply on that assembly.

The gas piston is not really a maintenance item on an M1 Carbine like on the M1 or M14 rifles. If you're concerned about damage to the peened site letting it work loose, just peen a new spot somewhere around the circle. It *should* need disassembly only once more in the barrel's life, if even that often.

We don't always get "better living through chemistry".

**4V50 Gary** · August 1, 2013, 12:04 PM

Do clean the inside of the gas cylinder the best you can. I'd use a brush and a scraper made from a flattened brass cartridge.

Dfariswheel · August 1, 2013, 05:51 PM

To clean the gas cylinder and the piston, you can soak then with a carbon removal chemical like Slip 2000 Carbon Killer, followed by brushing.

Use a soft wire to clear the gas port into the barrel. Ordnance used a specific size drill USED BY HAND to clean the port but be very careful. Damage or enlarge the port and the barrel is ruined.

The piston itself can be wiped clean with a Lead-away type cloth. These cloths wipe leading and carbon off by simple rubbing. (DON'T use on blued guns).
DO NOT use any steel scraper or tool to clean anything. Any scratches will cause the assembly to foul faster and worse.
DO NOT use any abrasive of any sort, including sand cloth, steel wool, Scotchbrite pads, etc.
If you want to scrape, use brass scrapers made from brass rod.

Use a brass brush to scrub the threads in the cylinder and nut.
After thoroughly cleaning, test fit the nut into the cylinder. If it seems to be sticky or damaged in any way, replace both the nut and gas piston. They're cheap and can prevent damaging the barrel.

Keep ALL lubricants, bore solvents, or anything else out of the gas assembly.
It's designed to be used bone dry.
With USGI spec ammo the Carbine gas system is self cleaning and lubricants and solvents will only burn into a sticky tar-like gunk that will cause the pistol to freeze.
Clean the Carine with the sights down on the bench to prevent solvents or lubricants from running into the gas system.

Last, Ordnance staked Carbine gas piston nuts to prevent them from unscrewing. Loctite would work, but will break down from the heat and the nut may unscrew, so staking is still best.
To stake, get a center punch and round the point off so it's not sharp.
Remember, the object is to move a little metal into the gas nut to prevent it unscrewing, NOT to put punch marks in the metal, so round the point well.

wileybelch · August 2, 2013, 02:28 AM

Thanks everybody! Job done!

Grump · August 2, 2013, 10:47 AM

HAH!

I don't feel like such a bad typost, since someone else rendered "piston" as "pistol".

Let the hyper-technical grammar Nazi pedantry begin! OR not.

amd6547 · August 2, 2013, 11:07 AM

Personally, I wouldnt mess with the carbine piston unless it stopped working.
When I got my CMP Inland, the piston didn't want to move...until I shot it...and it worked perfectly from the first shot.
Now it is loose like it should be.

July 31, 2013, 06:24 AM	#1
wileybelch Senior Member Join Date: May 16, 2009 Posts: 115	Stuck gas piston on M1 carbine How loose is the gas piston on the M1 Carbine supposed to be? I want to give my Carbine a thorough cleaning and the piston seems to be stuck as it won't budge after removing the retaining nut. Is there a safe/proper method for removal and subsequent cleaning?

July 31, 2013, 08:09 AM	#2
4V50 Gary Staff Join Date: November 2, 1998 Location: Colorado Posts: 21,829	Kroil. Soak it for twenty-four hours. __________________ Vigilantibus et non dormientibus jura subveniunt. *Molon Labe!*

August 1, 2013, 12:04 PM	#7
4V50 Gary Staff Join Date: November 2, 1998 Location: Colorado Posts: 21,829	Do clean the inside of the gas cylinder the best you can. I'd use a brush and a scraper made from a flattened brass cartridge. __________________ Vigilantibus et non dormientibus jura subveniunt. *Molon Labe!*

August 2, 2013, 11:07 AM	#11
amd6547 Senior Member Join Date: May 27, 2006 Posts: 2,313	Personally, I wouldnt mess with the carbine piston unless it stopped working. When I got my CMP Inland, the piston didn't want to move...until I shot it...and it worked perfectly from the first shot. Now it is loose like it should be. __________________ The past is gone...the future may never happen. Be Here Now.

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July 31, 2013, 08:38 AM	#3
Dixie Gunsmithing Moderator Emeritus Join Date: April 27, 2013 Location: Ohio Posts: 1,923	Kroil or any other penetrating fluid. What I do is use modelers clay, and build a dam around the piece stuck (leaving access to the stuck joint), forming a cup to hold a small amount of fluid in, which then soaks in over night.

July 31, 2013, 09:26 PM	#4
James K Member In Memoriam Join Date: March 17, 1999 Posts: 24,383	Wrap the jaws of pliers with copper or even friction tape and twist and pull it out. Jim

August 1, 2013, 04:39 AM	#5
wileybelch Senior Member Join Date: May 16, 2009 Posts: 115	Thanks, guys. While waiting for your replies, I soaked the piston with diesel fuel (rifle vertical to hold the solvent, I didn't have any Kroil) overnight. This morning I could rotate the piston but not pull it out (easily). Since there is so little gripping room on the piston, I tried to grab the end of the piston with the mouth of an empty .308 Win case which (after tapping lightly) nicely gripped the piston so I could rotate it and eventually wobble the piston out of the gas block. Sure enough, there was the usual black carbon fouling around the piston but it was now soft and easily wiped clean. What do you recommend for cleaning the inside of the gas block and how do you leave it after cleaning? Dry, lubed? What? Also, instead of peening the lock nut after reassembly, can a drop of LocTite 242 be used?

August 1, 2013, 10:52 AM	#6
Grump Member Join Date: October 22, 2008 Posts: 73	Re-assemble the piston dry. Threads? READ the temp specs on that Loc-tite 242 and then consider that normal firing rates raise the temp of the barrel and pistol above boiling. I'd want something that works above 350° F. and preferably to 450 or so. Metal always holds up, until reachuing the temps where it starts to lose temper. Beyond the scope of expected use, and even high-temp Loc-tite will melt or burn by then. I believe that most (if not all) will FIRST melt and stop locking before they burn and totally glue crap together. Peened metal is unlikely to "glue" itself together too badly, especially if some quality lube is used on the threads (no rust allowed). Obscure cold-weld and cold-solder concerns don't really apply on that assembly. The gas piston is not really a maintenance item on an M1 Carbine like on the M1 or M14 rifles. If you're concerned about damage to the peened site letting it work loose, just peen a new spot somewhere around the circle. It should need disassembly only once more in the barrel's life, if even that often. We don't always get "better living through chemistry".

August 1, 2013, 05:51 PM	#8
Dfariswheel Senior Member Join Date: May 4, 2001 Posts: 7,478	To clean the gas cylinder and the piston, you can soak then with a carbon removal chemical like Slip 2000 Carbon Killer, followed by brushing. Use a soft wire to clear the gas port into the barrel. Ordnance used a specific size drill USED BY HAND to clean the port but be very careful. Damage or enlarge the port and the barrel is ruined. The piston itself can be wiped clean with a Lead-away type cloth. These cloths wipe leading and carbon off by simple rubbing. (DON'T use on blued guns). DO NOT use any steel scraper or tool to clean anything. Any scratches will cause the assembly to foul faster and worse. DO NOT use any abrasive of any sort, including sand cloth, steel wool, Scotchbrite pads, etc. If you want to scrape, use brass scrapers made from brass rod. Use a brass brush to scrub the threads in the cylinder and nut. After thoroughly cleaning, test fit the nut into the cylinder. If it seems to be sticky or damaged in any way, replace both the nut and gas piston. They're cheap and can prevent damaging the barrel. Keep ALL lubricants, bore solvents, or anything else out of the gas assembly. It's designed to be used bone dry. With USGI spec ammo the Carbine gas system is self cleaning and lubricants and solvents will only burn into a sticky tar-like gunk that will cause the pistol to freeze. Clean the Carine with the sights down on the bench to prevent solvents or lubricants from running into the gas system. Last, Ordnance staked Carbine gas piston nuts to prevent them from unscrewing. Loctite would work, but will break down from the heat and the nut may unscrew, so staking is still best. To stake, get a center punch and round the point off so it's not sharp. Remember, the object is to move a little metal into the gas nut to prevent it unscrewing, NOT to put punch marks in the metal, so round the point well.

August 2, 2013, 02:28 AM	#9
wileybelch Senior Member Join Date: May 16, 2009 Posts: 115	Thanks everybody! Job done!

August 2, 2013, 10:47 AM	#10
Grump Member Join Date: October 22, 2008 Posts: 73	HAH! I don't feel like such a bad typost, since someone else rendered "piston" as "pistol". Let the hyper-technical grammar Nazi pedantry begin! OR not.