Guys I've got a problem child and I'm about at my wits end.
Well used Garand came into the Shop that had been fed (as stated by the Customer) a steady diet of 180gr. "Hunting ammunition" and the rifle had been fired bone dry enough to start seeing wear, and the forked rod was bent to the point it was contacting the op-rod, so I replaced both, installed a new recoil spring, finished up with a complete cleaning and proper lube with LSA.

First en-bloc of Danish Surplus went through without a any glitches.
Second one would eject, but short cycle, not picking up the next round....all the time I had for the day, and wanted to discuss replacing the Barrel with the customer because the one on it would swallow a case neck and had an ugly Importers stamp in big blue letters.

Installed a new Barrel, reamed & headspaced it, and again the first en-block of M2 Ball went through just like new, next one started skipping (failing to feed the next round) While there wasn't any real signs of wear between the gas cylinder and op-rod piston, I elected to try the two out of another M1 and the first en-bloc went through to I believe the sixth round and stopped with the base still in the enbloc and the bullet tip just out of the receiver, tried it again with the same result.
I also used the spring and fork from the donor rifle just in case the springs were "extra power"

Now at the time I did not have a Micrometer or the dimensions of the Gas Cyl or Piston but do now as found on Lane's Tips. (will check tomorrow)
We checked the recoil spring against two more new ones and the one from the rifle we cannibalized and they were within spec.

I do not have a Timing Block, or Gas Cylinder gauge, but am aggravated enough to buy them unless someone can point out the problem and the solution.
You know '06 Ball has gotten expensive, and I make sure its fully serviceable before returning it to the Customer.