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3/3/2025 5:00:57 AM EDT
I'm looking at the possibility that my gas system may be worn on my M1. I'll learn more tomorrow once I actually have tools to measure it with.

At the moment, I'm considering worst case scenario. That being, the gas cylinder itself is close to, or beyond .532 maximum inside diameter.

I don't want to replace the cylinder if I don't have to. Not only are new ones expensive, but I want to keep as much of this rifle original as possible.

If it is indeed at max or oversize, would installing an oversize gas piston solve the issue without creating any new issues?
3/3/2025 9:59:05 AM EDT
[#1]
Potentially yes. Columbus Machine charges $158 to match an oversize op rod piston to an oversize gas cylinder plus shipping both ways.

If your op rod piston is in spec, replacing the gas cylinder with an in spec unit will likely be the cheaper option.
3/3/2025 10:10:25 AM EDT
[#2]
Quote History
Originally Posted By HurstXJ:
Potentially yes. Columbus Machine charges $158 to match an oversize op rod piston to an oversize gas cylinder plus shipping both ways.

If your op rod piston is in spec, replacing the gas cylinder with an in spec unit will likely be the cheaper option.
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This.

I will add, unless you have a rare m1 garand none of the parts are original. They have been swapped out multiple times over the years.
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
3/3/2025 2:59:15 PM EDT
[#3]
Quote History
Originally Posted By TOTHEMAX:


This.

I will add, unless you have a rare m1 garand none of the parts are original. They have been swapped out multiple times over the years.
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My M1 is definitely a mix master. Nothing particularly rare or valuable about my particular M1.

I'm interested in this approach as the only gas cyls I can find are pushing $200. I can buy a new tip for $8, a 6" rod of 17-4 stainless for $13, and whatever my machinist friend would want to turn a new one. At most, $100 all in.
3/3/2025 5:14:55 PM EDT
[#4]
Check the CMP forum marketplace, in recent times an NOS SA gas cylinder sold for $150, good used SA $100, etc.

3/3/2025 5:27:59 PM EDT
[#5]
Quote History
Originally Posted By TheArcticWolf1911:



My M1 is definitely a mix master. Nothing particularly rare or valuable about my particular M1.

I'm interested in this approach as the only gas cyls I can find are pushing $200. I can buy a new tip for $8, a 6" rod of 17-4 stainless for $13, and whatever my machinist friend would want to turn a new one. At most, $100 all in.
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Quote History
Originally Posted By TheArcticWolf1911:
Originally Posted By TOTHEMAX:


This.

I will add, unless you have a rare m1 garand none of the parts are original. They have been swapped out multiple times over the years.



My M1 is definitely a mix master. Nothing particularly rare or valuable about my particular M1.

I'm interested in this approach as the only gas cyls I can find are pushing $200. I can buy a new tip for $8, a 6" rod of 17-4 stainless for $13, and whatever my machinist friend would want to turn a new one. At most, $100 all in.


Fair. If you have the means to fix it, by all means, fix it.
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
3/3/2025 5:56:43 PM EDT
[#6]
What issues are you having with the rifle?
3/4/2025 3:01:07 AM EDT
[#7]
Depends what I have it loaded with.

With PPU M2 ball, it'll run like a top.

However, in trying to handload my own for it, I'm having to bump up very close to max charges and the rifle won't fully cycle. It will eject, but short strokes and doesn't load the following cartridge.

I'm getting ready to actually measure the components and see if anything at all is out of spec, but I like to cover my bases and get a game plan together if something is, in fact, wrong.
3/4/2025 6:16:32 AM EDT
[#8]
Quote History
Originally Posted By TheArcticWolf1911:
Depends what I have it loaded with.

With PPU M2 ball, it'll run like a top.

However, in trying to handload my own for it, I'm having to bump up very close to max charges and the rifle won't fully cycle. It will eject, but short strokes and doesn't load the following cartridge.

I'm getting ready to actually measure the components and see if anything at all is out of spec, but I like to cover my bases and get a game plan together if something is, in fact, wrong.
View Quote

You might consider a different powder.  What are you using now?
3/4/2025 2:51:41 PM EDT
[#9]
I tried Varget, 4895, N-135, Accurate 2495. Hornady 150gr FMJ BT, 45gr charge each.

N-135 produced the best groups out of my rifle. I worked that one up in .5 increments to 47 grains. Max charge is 47.9. Rifle refused to cycle. Each and every test sample produced the same result. Case ejected, but did not pick up the next round. That's when I stopped and started hunting around, picking other user's minds.
3/5/2025 6:55:46 PM EDT
[#10]
short stroking could also be caused by a loose or a cracked gas screw(remove it and check back end) ,piston on op rod could be undersized,  new commercial stock? op rod may be rubbing, op rod spring out of spec,rifle not properly grease ,etc or a combination of these
3/5/2025 7:17:59 PM EDT
[#11]
Quote History
Originally Posted By TheArcticWolf1911:
I tried Varget, 4895, N-135, Accurate 2495. Hornady 150gr FMJ BT, 45gr charge each.

N-135 produced the best groups out of my rifle. I worked that one up in .5 increments to 47 grains. Max charge is 47.9. Rifle refused to cycle. Each and every test sample produced the same result. Case ejected, but did not pick up the next round. That's when I stopped and started hunting around, picking other user's minds.
View Quote


Factory ammo works fine, but none of your reloads do? Try loading a round in the chamber with the safety on, pointed in a safe direction, then try to eject it by hand. I'm thinking you didn't bump the shoulders enough and the case is getting pinched in the chamber increasing resistance to being ejected.

If the round is jamming because of headspace issues, you will feel that it's hard to eject manually.
3/6/2025 3:13:36 AM EDT
[#12]

I finally was able to get my hands on my calipers and measure the piston. Piston is undersized, (new one has been ordered) and the gas cylinder is in spec. Borrowed a pair of gauge pins from work while the ones I ordered get here. The stock it wears currently is an original set. It came with a reproduction set, but I didn't care for it. My mainspring also measures in spec.

My reloads use new, unfired brass. PPU. After the first batch of reloads didn't cycle, the stock set was removed entirely. Bolt, oprod, etc all removed and the entire thing got a kerosene bath. Everything was allowed to dry, given a coat of oil, then a generous coat of grease. Lucas Red-n-Tacky, just because that's what I had.

By no means is that exhaustive, but that should narrow it down. I'm reasonably confident that a new piston will alleviate the issue. That said, I'm all for things to check. I'll stick the plug in my pocket and put it under the microscope tomorrow.
3/6/2025 12:03:19 PM EDT
[#13]
Quote History
Originally Posted By TheArcticWolf1911:


I finally was able to get my hands on my calipers and measure the piston. Piston is undersized, (new one has been ordered) and the gas cylinder is in spec. Borrowed a pair of gauge pins from work while the ones I ordered get here. The stock it wears currently is an original set. It came with a reproduction set, but I didn't care for it. My mainspring also measures in spec.

My reloads use new, unfired brass. PPU. After the first batch of reloads didn't cycle, the stock set was removed entirely. Bolt, oprod, etc all removed and the entire thing got a kerosene bath. Everything was allowed to dry, given a coat of oil, then a generous coat of grease. Lucas Red-n-Tacky, just because that's what I had.

By no means is that exhaustive, but that should narrow it down. I'm reasonably confident that a new piston will alleviate the issue. That said, I'm all for things to check. I'll stick the plug in my pocket and put it under the microscope tomorrow.
View Quote


Still check your loaded ammo to make sure it ejects easily after it's been chambered. Just because your brass is new, doesn't mean that it fits.
3/6/2025 2:44:18 PM EDT
[#14]
I plan to. I just don't have any accessible to me at the moment.
3/6/2025 8:33:39 PM EDT
[Last Edit: FlipTopLid][Edited] [#15]
If factory ammo works then those powders and loads, 45gr of powder and 150gr bullets, should easily cycle the rifle.  

See if one of the new pieces of brass goes into and comes out the chamber easily.

I’ve not used new brass, only HXP and LC, does new brass need to be full length sized the first time?
3/7/2025 2:53:29 AM EDT
[#16]
I'm not sure if it needs it or not, but I did it anyway if only because the case mouths were out of round and I would have had a bear of a time getting a bullet in the cases if I didn't.
3/7/2025 4:45:20 PM EDT
[Last Edit: borderpatrol][Edited] [#17]
Quote History
Originally Posted By FlipTopLid:
If factory ammo works then those powders and loads, 45gr of powder and 150gr bullets, should easily cycle the rifle.  

See if one of the new pieces of brass goes into and comes out the chamber easily.

I’ve not used new brass, only HXP and LC, does new brass need to be full length sized the first time?
View Quote


The answer is, it depends. If headspace is good, meaning you have at least a couple thousandths clearance you may not need to size. Case mouths on the other hand need to be made round and neck tension uniform. That means a neck only sizing die or partial sizing in a full-length die.
3/8/2025 7:40:14 PM EDT
[#18]
Quote History
Originally Posted By FlipTopLid:
If factory ammo works then those powders and loads, 45gr of powder and 150gr bullets, should easily cycle the rifle.  

See if one of the new pieces of brass goes into and comes out the chamber easily.

I’ve not used new brass, only HXP and LC, does new brass need to be full length sized the first time?
View Quote


Finally got a handful of my reloads.

It chambers and extracts like it's not even there.

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