Briman,

I don't want to start a argument, but some where you have been given some information that is not quite up to snuff. Any semi-auto rifle that is gas operated has to deal with the same engineering problem. These rifles are designed to function within a narrow "gas port pressure" levels. The critical time is the instant that the bullet clears the gas port as it travels through the bore. Powders who's burn rate can create problems. Fast burning powders reach their peak pressure level before the bullet reaches the gas port. At the time the bullet clears the port, the pressure levels are already dropping. This results in higher than prudent pressure levels, and yet still not cycle the action due to low pressure levels at the time the bullet clears the gas port.
The use of powders that have to slow a burnrate develops its pressure peak much later than the fast powders. This has the potental to have a gas port pressure peak after the bullet has cleared the port. This will result in the action being subjected to higher than designed pressure levels. The action is cycled with higher than designed pressure levels and very possibly stress the action and result in damage. While it is possible to load different weight bullets, it is always necessary never to over look the demands of the resulting gas port pressure.

This is the situation as I understand it. I've been wrong before and will be wrong again. So if I'm wrong this time, I sure would like to know what the correct answer is.

.358,
I hope that this will illustrate the need for proper powder selection. You can expect to loose somewhere between 100 and 150 fps from velocities obtained in a bolt action rifle. This is the cost of using gas to cycle the action. I hope that this is of some help. Good luck and God Bless.