Get an adjustable gas nut
These are commonly referred to as a gas plug or a gas nut, but the correct designation is gas cylinder lock screw. (You install it to lock the gas cylinder in position, which will unscrew on the barrel threads without the lock screw in place.)
At any rate, the two available are the McCann and the Schuster. Each uses an orifice of some type to bleed pressure from the gas cylinder during the cycle. The McCann has a set of five screws, and the Schuster has a couple of setscrews that you move in/out to adjust the amount of bleed.
These devices are really simple, but there is generally no way to know in advance how to set them for any ammo you are contemplating using. Instead, you start with the port adjusted wide open (as large as you can set it) and fire & adjust until you just get reliable cycling.
I read about one shooter who made up several more insert orifices for his McCann adjustable nut (to fill in intermediate sizes), then D&T'd a small metal plate to hold all of them. The plate was just small enough to fit in the butt of a Garand. He numbered the holes and had a reference card for the ammo he would shoot that showed which insert worked for that type of ammo.
Of course, he had to develop the reference data the hard way, but he felt confident enough to just use his card to determine the correct orifice screw when changing ammo types.
This sounds like a really neat idea, and I think I'm going to do the same thing.
Let's face it. Surplus .30-06 isn't going to be available forever...and that's a shame.
