Hey Frank.

You may try the Remington factory slugs in the gun. They tend to be WAY smaller than the bore size and as far as pressures go, seem to be below Brenneke.
Before you bother reloading take them for a test drive. I have put them through a number of guns with no problems.

Where did you pick up the gun? Just got an Austrian cape myself.

Cheers

Tom

Carbonation without fermentation is tyranny