With the high quality of the GP-11 in 7.5x55 I am convinced the brass is of the highest quality as well. Being Berdan primed presents a challange but not a difficult one.
First getting some Berdan primers. That was accomplished a week back from a Gunbroker auction where I picked up 2k of PMC primers. If I live long enough to shoot that many Swisss rounds (my other milsurps would revolt) I'll be happy.
Next was getting the spent primers out. I tried an RCBS Berdan tool and have consigned it to the "going on Ebay" pile. I'm sure some folks can get it to work but It's more effort then I'm prepared to put forth.
So off to the hardware store. I picked up a 4' of 7/16th zinc rod for the princely sum of $3.00. I cut off a 5 1/2" piece as my de-priming tool and stored the rest for that project that I'm sure I'll need it for one day.
I chucked the 5 1/2" rod into the drill press and kept a recently fired GP-11 round nearby. Using a file and a piece of emory paper I reduced the diameter of the first 3" of the rod until it just fit inthe case mouth. The spinning drill press made it fast and easy. Just file, emory then check. You really want a snug but not overly tight fit into the case mouth.
Once the rod was ready I turned to the support for the cartridge case. A nearby hunk of 2x4 fit the bill perfectly. I drilled a hole about halfway through the 2x4 somewhere in the middle the same diameter as the base of the cartridge case. I then finished off the hole with a smaller diameter bit to allow the spent primer to fall away.
To use I place the 2x4 across a couple of scap 2x4 pieces to elevate the exit hole allowing the primers to collect without moving the wood. Placeing the three pieces of 2x4 either on a heavy rag or on a roasting tray (watch out for SHMBO) will facilitate cleanup. Pick up a fired case, fill it with water and place it in the hole in the 2x4. Place the depriming rod into the hole without pushing down to far then wack it with a hammer. I use a handy claw hammer that happens to be on my bench. You don't really want to be gentle but keep at least one foot on the floor. The water pressure will shoot the spent primer out cleanly (the GP-11 is crimped but they still come flying out) then you remove the cartridge case, dump out any remaining water and move onto the next case.
I have found that my old C press will easily rerpime the berdan primers despite the crimp with no de-burring requried.
I see no reason why one couldn't have several different depriming rods for the different calibers of Berdan primed calibers. I'm keeping the extra length of rod just in case I decide to make some more decapping rods! One never knows when such priceless odds and ends will come in handy.