Carlos speaks with the voice of many years experience, much oif it in competition circumstances. I, too, have been shooting Swiss schtuff, since the middle 1970's, but only reloading in the last year after the milsurp stuff hit $1 a bang here in yUK.
Let me add to Carlo's sage advice -
1. Case lube - Imperial Sizing Wax - a small tin will last you most of the rest of your llife - I reload seven different cartridges - maybe a hundred to hundred fifty a month, and a tin of the stuff lasts me about five years.
2. Remember that the GP11 bullet has a very specific ogive, and the K31 chamber is cut very precisely to accommodate it. Many after-market bullets will have a different shape in this vital area, and you'll need to replicate the original as far as possible, ensuring that the handload does not jam into the leade, raising pressure to an unacceptable level. If you don't have a Stoney Point chamber gauge, you can make an acceptable substitute and save many $$$$ like tthis....
3. Take a new cartridge case, full-length size it, then carefully, using a fine disc in a Dremel or similar, cut three or four slots vertically in the neck to take the bullet of your choice in a loose fit. Being a tightwad, I shoot the economy PPU 175gr bullets - near enough for my kind of shooting, but you might want to shoot Berger - your choice. Place the bullet loosely into the case neck - well proud of the correct length, so that chambering it and closing the bolt will push the bullet back into the case. Carefully insert the cartridge into the breech, and close the action gently but fully - remember - 12 o'clock = lock with the position of the serial number. Then smartly eject it into your hand.
4. Carefully measure the OAL of the cartridge, and subtract between 0.005" and 0.010 and use it to set your bullet seating die - the bullet will now be short of the lands in YOUR rifle. No other bullet will have precisely the same OAL. Remember, too, that this is OAL reduction measurement is not carved in stone - the 'sweet' spot will be there by trial and error. My K31 likes these particular bullets to be set 0.012" off the lands, but yours might be different.
THIS comes from the swissrifles.com site, courtesy of parashooter - one of the permanent live-in experts on all things connected with Swiss longarms -
When setting up a resizing die, one of the essential measuring tools is your rifle. Try a sized case in the chamber, with the striker on "half-safe" position (45 degrees) to take the mainspring out of the equation. If the bolt won't cam shut fairly easily (serial at 12:00), you need to screw your die in a little more and try again. Then try it with another case or two just to make sure everything is repeatable.
5. As a look at the tables Carlos has provided on the swissrifles.com site will readily show you - there are literally hundreds of powder/bullet combinations to play with, and powder selection is not overly critical - it if works well in a .308Win, then it will probably work just as well in the 7.5x55.
Basically, the GP11 cartridge has almost the same oomph as the .30-06 with the felt recoil of the .303 British. Not surprising, as the same man was responsible for the development of both cartridges. The British favoured a rimmed version and a more tapered case to aid extraction, and the Swiss did not. As it happens, the British Empire might just have adopted the Swiss-designed cartridge in the first place, and saved a load of expense down the line by not needing 'bendy' magazines for the BREN and having a much faster-firing HMG as well...
There is no doubt in my mind that the military issue GP11 in its standard format is the best military cartridge ever made anywhere. Trying to copy it will give you many pleasurable hours of shoulder thumping fun.
tac
