Military service rifles are "field" gage. They are not made to SAAMI specs. Like the above post mentions, you may be "over sizing" your cases. My dies just kiss the shoulder on my military guns. One the guns where I have several in the same caliber (7.62x54r, 8x56r, .303, etc) I have to adjust the dies every time I load for one gun. I also have to mark my ammo so it fits just the one gun. You can set your dies to "universally" size your ammo so you can shoot it in any of a specific caliber, but your brass just doesn't last as many reloadings.
Another thing to consider is most of these military rifles have come from storage. Most were gooped with cosmoline or similar preservatives prior to going into storage. At 35 degrees, cosmoline is about the consistency of a hard stick butter. You can cut it with a knife, but it tears the bread when you try to spread it. I have heard of several methods to cleaning the bolts (boiling in water, setting in a pan in toaster oven, etc) but what worked for me on most of my surplus guns was to put the bolts on a shop rag and run my handy dandy heat gun over the bolt assembly for a couple of minutes. (hair dryer should work also, but slower.) Cosmoline turns runny like melted butter and runs out. Simple bolt disassembly and wipe down and you are complete. No more goo slowing the firing pin.
If you find out the problem is oversized brass, load up about 10 grains of Unique and an unsized cast bullet that sticks into the rifling. This should hold your brass in place and let you fireform it to fit the chamber. This is practice I use when making Jap brass from -06 or similar. My 30 Bower Alaskan takes 12 grains of Unique, but that is 444 marlin brass necked down and is a little stiffer to form a shoulder.
Good luck and I hope you find the remedy so you can get that ammo to blast. Sounds like coyote weather and those irons should drop one in it's tracks.
Steve