I inherited a .264 from my grandfather last year that he had converted from a 1894 Mauser .308. He reloaded his own ammunition for it and there was not very much left when he passed. I really enjoy shooting this gun but virtually have no ammo left for it. I am having trouble finding ammo in the .264 caliber other then 140 gr. I have tried these and it shoots horribly. The ammo that he loaded that shoots incredibly well is 100 gr barnes with a 6.5x55 Lapua casing. Long story short I don't know enough about this round to know what round in the 6.5x55 family are equivalent. I've tried looking online but find myself getting more confused on the proper round for it and do not want to buy the wrong round or mess up this gun. all and any help would greatly be appreciated.

Looks like you got a 6.5 Swede there (6.6 x55). Lot's of good reloading data for that on many forums. Stick to conservative loads for that old action. My Swede (modern action Savage) likes the 120-140 grain bullets. Reloader 19 for 120-130 gr, and H4831SC or Reloader 22 for 140+ gr bullets.

6.5x55

First, if you have a properly head-stamped piece of the fired or un-fired brass, check to be certain what type of 6.5 you actually have. Even then, it might be good to have the bore 'slugged' to be certain of the dimensions and of exactly what cartridge the old girl is made for.
If it truly is the 6.5 Swede, you have one fine old cartridge/rifle combination. The '94 is a fairly strong action but isn't designed to take the more modern pressures of a lot of cartridges.

If you are looking for reloading information there are several places online that have some good information - Alliant, Hodgden, Nosler are just three. Most, if not all, will have loads for 100 gr bullets.
If you're looking for loaded, factory ammo, you'll have to search for it from the likes of Midway USA, Graf's and others. I picked up some Lapua factory stuff for my Swede in 123 gr loads and I believe they make some 100 gr stuff as well. I got mine from Graf's.
The older Mauser's and other older firearms cause the manufacturer's to load ammo for the Swede at somewhere below 50,000PSI. In a modern gun, this can be pushed up to 55-60,000

Thanks for the info and help. The spent brass is 6.5x55 Lapua stamped. I do have his recipe slips for the loads that he loaded for it. My grandfather was a gunsmith and did alot of work to the gun. It was the last one he was able to build before his health got to bad to do it anymore. I am pretty sure he upgraded the action on it as well. He was going to start teaching me to reload but his health went pretty fast shortly after we had started talking about it. Again thanks for the help and information. If it would help I'll post the recipe that was with the ammo if it will help.

If you need anything specifically loaded, let me know. I can duplicate his recipe for you.

Can you pm me some more details on duplicating the recipe. Says your inbox is full when I tried to pm you.