JBLEDSOE,
It looks like a couple pages already and I didn't even get to play. Generally I am not concerned with what others think is or is not safe if they have not tried it. So I am not concerned here.
I did the tube in the case with my 7-.300 Weatherby. It barely helped in the velocity and was not worth the effort. Years later I had it rebarreled to .375 diameter.
When I first had my K14 rebarreled to .375-8 Rem Mag I could not get the velocity I wanted. I started using different powders in combination. I discovered if the faster powder is against the primer, it acts like the faster powder. If you put the slower powder against the primer, you get a higher velocity than either of the powders will produce without the bolt getting sticky.
I remember chronographing for a friend with a 7X57 shooting 175 grainers. I think they were about 2700, but I could be wrong. It's been dacades. Most certainly I remember the velocities of the 300 grain Sierras: 3000, 3006 and 3000 feet per second. My buddy casually asked,
"What grain are those bullets?"
"These are 300 Sierras," I told him. I can still remember his outragesou exclamation.
"Those are rinocerous bullets!"
But then MRP became available and ran the same velocity without all the work of carefully keeping the cases upright and away from the bench so I didn't load two shots of the wrong powder. Stick in 100 grains and go shooting. When that was illegal to import, I switched to RL22 and had to drop back to 98 grains. The velocity fell off a little, but was so close, I didn't want to fool with duplex loads anymore.
I hope this is fun to read. It is fun to remember that guy's emotional reaction.
