M1 Garand gunsmith

**vetman03** · July 6th, 2023, 04:31 PM

Noah, PM sent.

**Delkal** · July 6th, 2023, 06:11 PM

Originally Posted by vetman03

Found the specs on the gas cylinder. It measures out that the inner diameter is out of spec. The end of the op-rod is at the very minimum of the spec. Put the two together and they would combined, not meet specs. Could be the issue.

Yes, that could be the issue. How did you measure the inside of the gas cylinder? They have special (and expensive) gauges but if you have access to some fired belted mag cases (like 7mm mag) you can use them. Turns out the belted rim is the same diameter as the gas cylinder internals and there is enough variation in the rims that you can find your own go and nogo gauges. You might have to go thru a lot of them with a micrometer but you can usually find cases that vary enough then you write the diameter on them with a sharpie and make your own set. But make sure the belt is round on the fired case.

Then scrub the fouling out of the inside of the gas cylinder and give it a light coat of oil. Very gently put your fired case "gauge" in the cylinder and see if it fits with no resistance. Since the case is brass you can make any of them fit with enough pressure so be careful.

Yes this is a crude hack but I checked a number of gas cylinders and could tell which ones were tighter. You still have to worry about if the gas cylinder is out of round but that is another story.

**vetman03** · July 6th, 2023, 06:39 PM

Measured the inside diameter with a digital micrometer. I get slightly different measurements depending on which axis I put it in. Either way, all of the measurments seem out of spec. Too large. I could try a new gas cylinder first, since the op-rod end is at the minimum spec. If I still have an issue, then replace the rod as well. Really want to get this working correctly. Puts out the 30-06 with little recoil. Last time at the range it was fun to shoot aside from the cycling issues. After this, I zero'd in the scope on a 30-06 Remington 700. What a difference in kick. The heavier Garand really takes the bulk of the energy.

The inside of the gas cylinder is clean and shiny. The measurements indicate is is probably out of round as well. It is a nice 1943 rifle. All of the marked parts are period correct for 1943. The op-rod was cut post war as they did back then to fix a cracking problem. The barrel was replaced post WW2 with a Marlin barrel, again what was normal post WW2. I do not have access to the 7mm cases myself. I will look around and maybe even look for a set of gauges. This is a long term investment for me.

**vetman03** · August 28th, 2023, 09:34 PM

Finally an update:

Went through various part changes, one at a time to insure what was working and not working. Found excessive wear on the bullet guide and part of it slightly bent, but that was not the issue. The problem was the gas cylinder. The tolerances between the end of the op-rod and the input of the gas cylinder were only about .002 combined. I had some delays in working on this, but a new gas cylinder along with a new op-rod solved the problem.

**Story** · August 29th, 2023, 09:58 PM

Originally Posted by vetman03

Finally an update:

Went through various part changes, one at a time to insure what was working and not working. Found excessive wear on the bullet guide and part of it slightly bent, but that was not the issue. The problem was the gas cylinder. The tolerances between the end of the op-rod and the input of the gas cylinder were only about .002 combined. I had some delays in working on this, but a new gas cylinder along with a new op-rod solved the problem.

Thanks for circling back with the update.