I examine a GI M1 Garand and when I attempted to open the breech, the bolt would only open 1/2 to 3/4 of the way ?

assembly incorrectly or defected part ?

Jimmy

Off hand, I would say something was assembeled incorrectly. Take out the trigger group to examine. Next try to get the bolt out. Go to jouster forums and ask in the M1/M14 forum. Someone there would know for sure.

I maintain all the M1s for the honor guard at the Amvet post I'm a member of my best guess without seeing it would be incorrect assembly.
About the only thing that would cause the symptom you're describing would be the follower due to the op-rod not working correctly.

There's a couple of pieces that can reassemble
upside down in the Garand. Don't mess with the
bolt yet.

#35, the follower rod, will fit upside-down into the operating rod
catch, and will bind the action, IIRC. Not sure it would assemble
into stock without effort like that...

The follower, #29, can also be assembled upside-down. Don't
know the effects from that, I haven't made that mistake, yet.

I think Andy52 has identified the most likely problem.

Could be an opportunity there for you, Jimmy! Current owner might be willing to consider a low-ball offer to get that defective rifle off his hands! Detail strip the piece, reassemble correctly, and have a pretty good deal. Even if a part or two needs replacement it shouldn't be too difficult or expensive to get it working properly.

#35, the follower rod, will fit upside-down into the operating rod
catch, and will bind the action, IIRC. Not sure it would assemble
into stock without effort like that...
Correct, the rod can be installed upside down don't know if the stock would fit if that happened I've never tried that. Next time I'm working on the rifles I'll have to try it just for grins.

Good Morning Jimmy:

Steve912 has a drawing of the assembly and disassembly of the M-1 Garand. He suggests, and I concur, the follower arm and guide maybe assembled upside down and would prevent the bolt from completely opening. I would remove the trigger guard assembly and the stock. The Guide rod and spring would then be removed. Check the bolt if it has free movement in the gun. Assembly the guide rod and arm as the diagram illustrates. If you have any questions, PM me and I will guide you in the process. I have a M-1 Grand and also inspect the Grand and 03's at the post 79 in New Port Richey.

Nick

__________________
NRA Instructor\GCA Gunsmith

The only time I have ever seen the problem that the OP has is if the rifle has a broken op rod spring.

As a few others have noted the follower rod can be inserted upside down and it then causes the spring to drag on the operating rod, preventing the bolt from going all the way back.

Pull the rifle out of the stock and check fore that. The long bit should be close to the barrel and parallel to it.

However, while you have the follower rod and spring out, put it back together with those parts out and then tilt the rifle back and forth. The operating rod and bolt should travel back and forth easily under their own weight as the rifle is tilted for and aft. There should be no contact with the stock.

Also check the operating rod to ensure it is straight. The end with the piston, the bit just before the slide, and the slide portion itself should all be parallel and the first two should be in the same vertical plane. If not, the op rod is bent.

Back in the High School ROTC days, we had to learn how to dis-assemble and re-assemble the M-1 Garand blindfolded.
One thing we learned was if you assembled the follower upside down,,the follower would "fly out" with a KA-PING sound when it hit the concrete floor of the basement Armory.
Very embarrassing.

A M1 op-rod normally has two vertical bends and no horizontal bends. Attempting to straighten out the rod will destroy a $100 part.

Some one gets an M1 through CMP and suddenly they are either an expert or a critic. Yes, a "straight" operating rod does have bends in it. At no point did I suggest someone should "straighten" those bends.

Re-read what I wrote:

"Also check the operating rod to ensure it is straight. The end with the piston, the bit just before the slide, and the slide portion itself should all be parallel and the first two should be in the same vertical plane. If not, the op rod is bent."

In order for those three areas to be parallel, the operating has to bend upward toward the barrel and then bend back again to run parallel to the barrel so that the piston head on the end of it runs true in the gas cylinder. If that's not happening, accuracy will suffer and the gas cylinder will have excessive wear.

Viewed from the side, the slide and the end of the rod near the piston must be parallel. Viewed from above, the round portion of the rod should be straight, and the slide should be parallel to it.

The angle and of those bends is critical and with an abused operating rod the angles won't be right and the rid won't be aligned in the right places.

----

And for what it's worth, you'll be hard pressed to find an operating rod that is within spec for $100. $150 is about where a good replacement operating rod starts.

It is what it is, man.

JimmyJ, how'd it all turn out?

Guess you would have done better to just Google it than to ask here. Some people are so sensitive. The CMP website has lots of information on Garands, as does the CMP forum.

I had that happen once. I incorrectly assembled the action after cleaning. If I recall correctly it’s the fitting of parts 30 and 31 in the earlier diagram.