Build-up scaring on inside of M1 Carbine Slide - The Firearms Forum

gary.matcek · 01-01-2012, 05:57 PM

Happy New Year, All

I have a National Postal Meter, US .30 caliber M1, with a 1943 barrel. I shoot it often and during cleanings I have notice what appears to be scaring or build-up inside of the slide where the gas cylinder makes contact with slide (see pictures).
At first I thought it to be powder discharge or carbon that one might expect to leak from the gas port, but the solvents and lubricants I use during cleaning do not reduce or remove.

Appreciate any advice/ opinion you all my have. Is it common to see buildup at this location ? Is it potentially a hazard or safety concern?

Thanks,

Gary

gary.matcek · 01-01-2012, 06:28 PM

Happy New Year, All

I have a National Postal Meter, US .30 caliber M1, with a 1943 barrel. I shoot it often and during cleanings I have notice what appears to be scaring or build-up inside of the slide where the gas cylinder makes contact with slide (see pictures). At first I thought it to be powder discharge or carbon that one would expect might leak from the gas port, but the solvents and lubricants I use during cleaning do not reduce or remove.

Appreciate any advice/ opinion you all my have. Is it common to see buildup at this location? Is it potentially a hazard or safety concern?

Thanks,

Gary

JLA · 01-01-2012, 07:19 PM

Its just baked on carbon. Understand that the gasses directly behind the bullet are at around 35000 PSI in the .30 carb. Thats alot of pressure, which amounts to alot of heat. It will come off, but you will have to soak it overnight and use a pick to break it up.

Jim K · 01-01-2012, 08:30 PM

A sharpened broad blade screwdriver will take it off. Just don't dig into the metal, only into the carbon. That buildup is more than normal and may indicate a serious leak, but then I don't know how long it has been since the carbon was cleaned off. You might want to check the piston and piston nut and make sure they are correct and fitted properly.

Jim

gary.matcek · 01-01-2012, 08:46 PM

Quote:

Originally Posted by JLA

Its just baked on carbon. Understand that the gasses directly behind the bullet are at around 35000 PSI in the .30 carb. Thats alot of pressure, which amounts to alot of heat. It will come off, but you will have to soak it overnight and use a pick to break it up.

gary.matcek · 01-01-2012, 08:55 PM

JLA,

Thanks

Jim,

I recall that I could see some threads of the gas piston nut extending out of the gas port. Should that nut be flush, all the way in with no threads visible?

Gary

StoneChimney · 01-02-2012, 07:16 AM

What does the gas piston look like?

Jim Hauff · 01-02-2012, 11:58 AM

Looks to me like very dense (graphitized) carbon build up. Try working on it with a dental pick - see if you can chip or lift some of it off the steel. Removing this stuff, if it is as I suspect, chemically, is difficult but can be done by getting something to penetrate under the build up - it occurs in very thin sheets and the carbon atoms have a high affinity for bonding with iron and with each other under high heat and pressure. Mechanical removal may be in order.

gary.matcek · 01-02-2012, 06:27 PM

Thanks, Jim.

StoneChimney asked me what the gas piston looked like, so I have posted pictures of same.

Threads of the gas piston nut appear to extend out away from the gas port. Should that be flush, with no threads visible?

Thanks,

Gm

01-01-2012, 05:57 PM	#1
gary.matcek Member Join Date: Jan 2010 Posts: 42	Build-up scaring on inside of M1 Carbine Slide Happy New Year, All I have a National Postal Meter, US .30 caliber M1, with a 1943 barrel. I shoot it often and during cleanings I have notice what appears to be scaring or build-up inside of the slide where the gas cylinder makes contact with slide (see pictures). At first I thought it to be powder discharge or carbon that one might expect to leak from the gas port, but the solvents and lubricants I use during cleaning do not reduce or remove. Appreciate any advice/ opinion you all my have. Is it common to see buildup at this location ? Is it potentially a hazard or safety concern? Thanks, Gary Attached Images -->

01-01-2012, 06:28 PM	#2
gary.matcek Member Join Date: Jan 2010 Posts: 42	Build-up scaring on inside of M1 Carbine Slide Happy New Year, All I have a National Postal Meter, US .30 caliber M1, with a 1943 barrel. I shoot it often and during cleanings I have notice what appears to be scaring or build-up inside of the slide where the gas cylinder makes contact with slide (see pictures). At first I thought it to be powder discharge or carbon that one would expect might leak from the gas port, but the solvents and lubricants I use during cleaning do not reduce or remove. Appreciate any advice/ opinion you all my have. Is it common to see buildup at this location? Is it potentially a hazard or safety concern? Thanks, Gary Attached Images

01-01-2012, 07:19 PM	#3
JLA TFF Moderator/Host Join Date: Feb 2007 Location: Heart Of Texas Contributor Posts: 17,319	Re: Build-up scaring on inside of M1 Carbine Slide Its just baked on carbon. Understand that the gasses directly behind the bullet are at around 35000 PSI in the .30 carb. Thats alot of pressure, which amounts to alot of heat. It will come off, but you will have to soak it overnight and use a pick to break it up. __________________ It takes 43 muscles to frown, 17 to smile, and 3 for proper trigger squeeze. The latest caliber or gear is no substitute for experience and skill. Rifles and cartridges don't make hits -- shooters do. Fact of life: After Monday and Tuesday, even the calendar says WTF!

01-01-2012, 08:30 PM	#4
Jim K Advanced Senior Member Join Date: Dec 2009 Posts: 6,408	Re: Build-up scaring on inside of M1 Carbine Slide A sharpened broad blade screwdriver will take it off. Just don't dig into the metal, only into the carbon. That buildup is more than normal and may indicate a serious leak, but then I don't know how long it has been since the carbon was cleaned off. You might want to check the piston and piston nut and make sure they are correct and fitted properly. Jim Last edited by Jim K; 01-01-2012 at 08:31 PM..

01-01-2012, 08:55 PM	#6
gary.matcek Member Join Date: Jan 2010 Posts: 42	Re: Build-up scaring on inside of M1 Carbine Slide JLA, Thanks Jim, I recall that I could see some threads of the gas piston nut extending out of the gas port. Should that nut be flush, all the way in with no threads visible? Gary

01-02-2012, 07:16 AM	#7
StoneChimney Advanced Senior Member Join Date: Nov 2010 Posts: 1,087	Re: Build-up scaring on inside of M1 Carbine Slide What does the gas piston look like? __________________ Full service gunsmithing and firearm manufacturing shop. Licensed FFL 07/02 Manufacturer. Visit our website!

01-02-2012, 11:58 AM	#8
Jim Hauff Advanced Senior Member Join Date: Apr 2008 Location: Lehigh Valley, PA Posts: 2,980	Re: Build-up scaring on inside of M1 Carbine Slide Looks to me like very dense (graphitized) carbon build up. Try working on it with a dental pick - see if you can chip or lift some of it off the steel. Removing this stuff, if it is as I suspect, chemically, is difficult but can be done by getting something to penetrate under the build up - it occurs in very thin sheets and the carbon atoms have a high affinity for bonding with iron and with each other under high heat and pressure. Mechanical removal may be in order. __________________ Jim Hauff ~ H&R Collector In Memory of Bill Goforth and Jim Ritchie

01-02-2012, 06:27 PM	#9
gary.matcek Member Join Date: Jan 2010 Posts: 42	Re: Build-up scaring on inside of M1 Carbine Slide Thanks, Jim. StoneChimney asked me what the gas piston looked like, so I have posted pictures of same. Threads of the gas piston nut appear to extend out away from the gas port. Should that be flush, with no threads visible? Thanks, Gm Attached Images