M1 Rifle short stroking

[Grizzman]

I'll take my M1 Rifle short stroking experience as an opportunity to create the first thread in the Help Me Fix My Gun category.

The M1 passes the tilt test, and the op rod moves smoothly with no binding or contact with the stock or sling swivel band. I also replaced all springs with ones from Orion 7.

I had been trying between 45.5 and 48.0 grains of IMR4064 and Varget with 168 grain Hornady A-Maxes in LC Match brass set off by CCI #34 primers seated to 3.240" to 3.330" COAL.

The supplier of the M1 sent me a different op rod and gas cylinder, which made no difference. I then bought some Greek HXP mil surp ammo, which ran fine. Since it runs with mil surp, he says the problem is my handloads, not the rifle, and will not assist with any more troubleshooting.

I bought a pound of H4895 which should have the ideal burn rate and used between 45.5 and 47 grains with the above mentioned details with the same short stroking results.

I then switched to 150 grain Sierra GameKings, thinking possibly it just doesn't like the 168s and loaded 8 each with 47.0, 47.5 and 48.0 grains of H4895 (with the above details). I experienced multiple short strokes with the 47.0 and 47.5 grain loads, but made it through the clip with 48.0 grains....but that was a fluke as it didn't work in a 2nd test.

I tore down a few of the Greek cartridges, and they had 52 grains of a ball powder with 150 grain FMJs. I loaded 49.5 grains of the Greek powder with 168s (and the above details) with success.

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I decided to get a McCann gas regulator to try with IMR 4350, figuring I could get it to run properly in that configuration. I tried it with 51 to 53 grains, and even with the smallest gas venting aperture, I got the same results as before. I fired a few rounds of the 51 grain load with stock gas cylinder screw, and it cycled them fine (brass was flying to approx 12:30 to 1:00.

I then bought some somewhat faster H414, and loaded up some test rounds with between 50 and 52.5 grains. It fed every time with all the loads, and the brass was going to between 1:00 (most between 1:30 and 2:00) and 2:30, which is more appropriate.

My current idea is to locate someone local with an M1 so I can meet them at a range to try their op rod and/or gas cylinder in mine, with 46.5 grains of Varget driving 168s. Hopefully this will allow me to determine if the gas system is the cause of the failures. I use Varget in my 308 Win loads, so would really like to use it in my M1 also. H414 may work, but it's not appropriate.

Do I have an volunteers that are local to KC. I've loaded up 104 rounds of ammo for the test, and can make up some more.

Does anyone have an M1 gas cylinder gauge I could borrow?

Does anyone have experience with Columbus Machine Works in case the op rod piston is to blame?

Does anyone have any other ideas on what else to check?