You'll find a variety opinions about whether or not current commercial ammo is safe to fire in a Garandicon. The Garand gas system was designed around M2 ball ammo using IMR 4895 powder. It is generally accepted that full power loads using powder slower that IMR 4064 and bullets heavier than 180 gr can damage the operating rod. Some say it can't/won't. Last year, I asked Remington what of their 30-06 loads they recommended for use in the Garand. They replied that they did not recommend any. So, I stick with M2 ball or equivalent loads.

However, if you use an adjustable gas plug, you can regulate the amount of gas driving the op rod and reduce the port pressure. I don't see why you could not use any ammo if you first open the plug all the way, releasing all the gas, and then close it in increments until the gun cycles reliably.

All this presupposes that you are using a Garand in tip top shape with no worn or out of spec parts. For one thing, I'd replace the op rod spring with one made by Orion 7; they are the best made today. No matter what ammo you use, replace the op rod (and clip latch) springs. The USGI springs may be too short; worn (shiny spots) or rub marks; kinked or even broken. The op rod spring is the only thing that keeps the bolt from hitting the heel of the receiver.