cycling failure.

[jbernat315]

I am relatively new to the M1 World and would appreciate some assistance in figuring out a problem that I have with my M1 Garand. When I have tried firing my rifle, it would eject the old cartridge; however it would not chamber the next round, giving the impression that it was a short cycling problem. I thought that there might be a problem with the gas cylinder or the operating rod, however after trying a different gas cylinder and having someone check the operating rod, the problem still remained. I checked the operating rod to make sure that it was not rubbing against the stock, and that works fine without any rubbing. All of the moving parts have been cleaned greased as suggested. It was mentioned that the barrel was possibly a replacement and was wondering what the proper gas port diameter is for the hole from the barrel to the gas cylinder is. Any suggestions would be appreciated as to what could be wrong - thanks.

[Prince Humperdink]

First off,Welcome!2nd,when You say the op rod was checked was it for the bend?Did You have the piston diameter checked?Your Gas cylinder could also be out of spec allowing enough gas to pass by that it cannot cycle.I had a case where this happened when I used a worn piston in a worn gas cylinder,but when I used an op rod that was in spec it worked fine,and the worn piston functioned with an"as new" gas cylinder.HTH,
Ryan

[jbernat315]

The operating rod was checked to see if the piston was in spec, which it was; They did also say that they thought that the rest of the operating rod looked fine also. I have tried two different gas cylinders (the original and a a "newer" cylinder) both had relatively the same preformance.

Jonathan

[timshufflin]

What ammo you shooting? I know, seems dumb, just humor me LOL.

[Punch The Clown]

De-linked LC I'll bet.

[jbernat315]

Currently I am firing Remington 150 grain commercial rounds. I have heard that I should use military surplus rounds, or an adjustable gas plug but I am working on that.

[howie]

Commercial ammo is not good without an adjustable gas plug. Please don't ask how I know. It's too painful to think about. I think I'll get a few "amen's" from the brethren when I tell you not to shoot any more commercial stuff until you get an adjustable plug.

[timshufflin]

Okay, LC ruled out. Here's some things on my list that I see most commonly. Others here always have great idears too so you'll get lots of feedback.

You ruled out piston, oprod rub and cylinder so here goes
1. Poppet valve in the gas cylinder. Make sure it's not cracked at the bottom. Make sure it's not stuck open with sand or something. Clean it.
2. When you fire the 8th round does the bolt hold open? If so, try an oprod spring of less power. If not, try a new oprod spring. There's Orion 7 and Wolff for starters.
3. Gas port is about 5/64 +or-. Depends on commercial or GI barrel. Shouldn't be larger than 5/64ths though.

[jbernat315]

ok, the bolt does not remain open after the 8th shot. Tim, are the springs you suggested for a situation where the bolt does not stay open after the 8th shot?

[jbernat315]

... and the gas port is approx 5/64

[timshufflin]

The bolt not staying open means that you don't have a spring which is so weak that the bolt is flying past the ammo before the ammo can be lifted. You simply have a gas situation which could be

A. A leak like the gas lock screw
B. Out of spec piston or cylinder

Now, this said, I know nothing of the ammo you're shooting and it could be lame stuff. Try some HXP and see what happens. If you still have the issue, try a slightly worn oprod spring.

Just tough to diagnose with no gun in your hand :)

[themeowman]

Not Tim, but if the bolt does not stay open the op rod sping is weak & not
pushing the bolt back far enough to pick up the new round. I have had good
results with the Orion 7 spring, have not tried the Wolff. Hope this helps.
Tom

[timshufflin]

See themeowman, I would say that the spring is plenty strong and the gas can't push the bolt/oprod far enough back to hold the bolt open and let the clip eject. Hey, I could be wrong though.

That's another thing, does the clip eject after the last round? They usually don't when you don't have the gas and the spring is strong enough.

[themeowman]

Tim, thanks for the explanation. I did not think of the gas not overcoming the
spring. I have always thought of a weak spring. It is great to keep learning. I
am now even more curious to see what the answer is!
Tom

[timshufflin]

themeowman, I'm not saying that I'm right bro. I just think I might be. I had this very issue with someone on this very forums rifle today. I switched the spring out for a slightly weaker one and the rifle worked. Here's the thing though, I was using LC and that stuff is the weakest ammo I know of. This rifle sounds like there's a gas leak somewhere. We have the cylinder, piston or screw. Something is up.

[jak]

The operating rod was checked to see if the piston was in spec, which it was; They did also say that they thought that the rest of the operating rod looked fine also. I have tried two different gas cylinders (the original and a a "newer" cylinder) both had relatively the same preformance.

Jonathan

First, Welcome to the forum
Who are "they" that you mentioned in your post ? A gunsmith ? The place or person you bought the garand from ? I'm just curious as to "they's" level of knowledge on the garand because "they" should have told you about the ammo.

Also, what is the part number on the op rod ? Is it something like "7790722-SA" ? I am asking because I had an op rod that like that and it caused a short cycling problem on my rifle. That part number is a National Match op rod and it rubs against the barrel a lot more than a regular op rod.

[musketjon]

Saying the gas hole should be ABOUT 5/64 is like saying 1/8 of an inch is ABOUT a half-inch. You need to be a little more precise. Unfortunately the drill sizes to use for go/no-go gages escapes me right at the moment. If the hole is too small, not enough gas gets into the chamber to work the op rod. If it's too large, too much gas gets into the chamber and damage to the rod could be forth-coming.
Jon

[cannonshooter]

Do you have the Gas Cylinder on to far down? That will cause the issues you are saying. The window should have the gas port centered in it and the handguard should have some play in it.
Mack

[jbernat315]

Tim- the clip does not eject after the last round is fired.
jak- "they" is an individual that I was referred to by a gunsmith who had more knowledge in M1's than he did. He was also the one who suggested getting the adjustable plug and/or military surplus ammo. the part number is 6536382-J.
Musketyjon- I measured the hole by putting a 5/64drill bit into it. it fit snugly into the hole.
cannonshooter- the gas port holes line-up.

[timshufflin]

Saying the gas hole should be ABOUT 5/64 is like saying 1/8 of an inch is ABOUT a half-inch. You need to be a little more precise. Unfortunately the drill sizes to use for go/no-go gages escapes me right at the moment. If the hole is too small, not enough gas gets into the chamber to work the op rod. If it's too large, too much gas gets into the chamber and damage to the rod could be forth-coming.
Jon

I'll give you that Jon but the precise GI hole size escaped me too. I do know the commercial size and that is 5/64. The GI size will never be to small so if it is no larger than 5/64 than we're all set. Sometimes, I just say what I know in order to move stuff along. Feel my love baby.

[timshufflin]

Tim- the clip does not eject after the last round is fired.
jak- "they" is an individual that I was referred to by a gunsmith who had more knowledge in M1's than he did. He was also the one who suggested getting the adjustable plug and/or military surplus ammo. the part number is 6536382-J.
Musketyjon- I measured the hole by putting a 5/64drill bit into it. it fit snugly into the hole.
cannonshooter- the gas port holes line-up.


So this is a Commercial barrel or GI barrel? 5/64 hole size is fine, no problem there. We know this much, I think;

1. The piston is correct size
2. Cannonshooter makes a good point. Not only make sure the barrel port is centered in the gas window of the cylinder but also that you unscrew the gas lock as much as you can allowing the cylinder to come off the rifle as much as possible with the hole still in the window. Then install your lock screw.
3. We don't know if your gas cylinder, either one, passes spec
4. We don't know how long your oprod spring is.
5. We don't know if the ammo you're using is even as potent as GI HXP.

[rlelvis]

Look no further, I am the “they” that looked at jbernat315’s M1. And knowing what I don’t know I referred him here. I happened to be at the gun shop trading a M1 for a new duck gun, yes it hurt to do it, when jbernat315 brought in his M1.

The piston is .5262 and round, a visual inspection of the oprod did not reveal any obvious ‘bad bends’ but there was contact between the op rod and the stock. Tilt test failed so we identified the contact points and he said he relieved it and it now passes. No gauge to measure either of the gas cylinders. The gas lock screw appeared to be OK. It was lubed and there were no obviously worn parts. After finding out he was shooting commercial ammo I did visually inspect the receiver for any signs of cracking, nothing. My first guess was the op rod contact so I recommended he fix that and get some HXP or an adjustable gas plug before shooting/troubleshooting any more.
Things I did not check include headspace (no gauges available then), chamber finish/cleanliness, barrel spline diameter, spring test, or muzzle wear. I was betting the oprod contact would solve the problem.

I think it would be good to get a new spring in it and some HXP.

Jbernat315 - Hopefully we can link up at the range and I will supply the HXP, spring and if needed swap a few more parts for troubleshooting while there. I can also try to borrow a gas cylinder gauge to check them.

Aren’t the correct drill index numbers 47 and 46 go and nogo? My book is loaned out but these are marked in my index. Or am I total out there on these?

[timshufflin]

Another point Elvis just made me think of, check the inside of the oprod for a piece of old spring. There is to much spring on this rifle or not enough gas. If it tilts, it has to be one of these two.

[timshufflin]

Oh, check the back of the stock for bolt strikes on the inside. If so, get that cleaned out. This was per Punch The Clown

[herrmann]

Two more things:
1. Back the lock off one turn from wherever it is.
2. Grease the op rod spring generously.

[cuppednlocked]

Bob,

What duck gun did you get?

[jbernat315]

Ok - rlelvis and I got together yesterday and started swapping parts to figure out what was not functioning properly.

1) The gas cylinder had some play in it allowing for gas to escape at the gas port before it reached the gas cylinder.
2) The gas plug venting spring was not functioning properly, likely allowing gas to escape the cylinder.
3) There may be a problem with the operating rod because when that was swapped it worked before changing out the gas cylinder and plug.

I have the gas cylinder and an adjustable gas plug, so it appears to be cycling properly now. Probably going to chang the operating spring and perhaps look into operating rods.

The only other issue noted at this point is that it tends to flatten the primer of the casings.

[timshufflin]

Regarding number 1. , told you punch the clown! Punch and I discussed that one on the phone. It is a small amount of gas to be lost but it adds up. Here's the thing though, just tightening the cylinder won't help. If this is truly a problem then only a new cylinder or barrel will fix it. There would be a gap there that needs closing.

[timshufflin]

I don't understand number 3.

[Punch The Clown]

The only other issue noted at this point is that it tends to flatten the primer of the casings.

Commercial ammo? Dry chamber I hope.

[Punch The Clown]

I don't understand number 3.

That goes back to broken spring scenario.

[rlelvis]

jbernat315, correct me if I missed something here.

Long story short, as the rifle was HXP would not cycle. Changed the op rod spring and got about 1 in 3 to cycle. Changed the op rod and used the old spring and got about 4 in 5 to cycle. Changed both and got maybe 7 in 8 cycle. On closer inspection the poppet valve tension was tight but after cleaning with Hoppes it freed up and revealed a bad spring and no tension, only closing partially. We swapped it out and cycling improved. OP also has a Shuster gas plug but ammo was gone before we were able to get it adjusted. Also found that the gas cylinder/barrel fit was very loose, diameter, and allowing a notable amount of gas to escape between the barrel and gas cylinder. This is a commercial barrel but a second gas cylinder fit correctly and fixed this. Both cylinders lined up dead center. I do not have a gauge or pins to check wear but with the other changes cycling was good.

Looks like it is a combination of factors. So with proper adjustment on the Shuster plug (or replacement) and a new spring I think cycling will be fixed. Now the op rod that is marked 6536382-J, stamped on the bottom just in front of the handle, I have not seen this before? The tip measures and a visual comparison of the op rod with another does not show any ‘bad bends’ for what that’s worth. There could still be something amiss on it though. The tab is well worn but not too far, yet. There are some wear or rub marks on the op rod that almost look like they were caused by excessive flexing? My guess is that this could be from commercial ammo? Or could have been rebuilt at some point. Could there be another cause? There was originally some contact with the stock that caused it to fail the tilt test but that was fixed.

Any thoughts or ideas on the op rod or cycling diagnosis? I am far from experienced with troubleshooting and don’t want to give bad info or miss something. So if I am out there floppin again, call it. ;)

[rlelvis]

I don't understand number 3.




It did function, not 100% though, by just changing the op rod. This was with the bad valve, loose fitting gas cyl and org spring? Why I am still up in the air on the op rod?

[rlelvis]

Commercial ammo? Dry chamber I hope.


HXP, dry. Some more notable than others.

[Punch The Clown]

elvis, I still would measure inside of the op-rod tube. Use a dowel and make sure it measures the same as a known good op-rod. I've seen them with crap, gunk, pieces of spring etc. down in there. Also, someone could have replaced the piston with one that was machined too long. What if they left the part that goes inside the op rod 1" long. The rifle wont cycle. Also, I read an interesting bit from 50 years ago but of course I can't find it now. Anyway, seems like the design relies on the bolt striking the heel on recoil. Tim had a prob with a batch of stocks a while back that had too much wood there. The stock was stopping the bolt short.

[Punch The Clown]

http://i369.photobucket.com/albums/oo140/Stumedic/oprod1_640x480.jpg

http://i369.photobucket.com/albums/oo140/Stumedic/oprod2_640x480.jpg

I just had my nails done.

[Cal30M1]

I just had my nails done.

I was gonna ask!

[timshufflin]

I was gonna ask!


REally really really really funny.

[rlelvis]

So whats the deal with the op rod #. I got no idea. Who, what, when, where???

[nstoolman1]

Thank you all for a very informative thread. $clapper$

[jbernat315]

Hey- rlelvis and I were curious if anyone knew what the origins are of the op rod on my M1. rlelvis had mentioned to me that he did not recognize the serial number that was printed on my op rod. I tried to get a picture that shows the detail as much as I could.

[jbernat315]

haha oops- here is the photo of the serial number.

[Orlando]

Huh, thats a new one to me. Nothing stamped in the normal spot?

[jbernat315]

nope- that is the only marking on it.