One thing you may encounter with Milspec brass, especially if fired in an M-1 or BAR or MG, is the base may be expanded slightly, making full length resizing a bit more difficult. You can either try chambering a case in whatever .30-06 rifle you intend to use it in, or buy a special resizing die, or just muscle it, being sure to lube the case just forward of the head. I've done that with TW-54 brass in the past, and it only needs to be done once unless you are shooting it in an M-1 rifle, in which case, if it chambers, you can probably not have to do it. Oh, and I never used the special resizer, just the regular RCBS one.
The Milspec brass will have slightly less internal capacity than commercial, so you should probably back off the charge a grain or two. DO NOT use loads of slow-burning powders that are less than 10% of a full charge load, however. 48.5 gr of IMR 4895 or 48 gr. of IMR3031 works great in a Garand. IMR4065 is the slowest powder that should be used in the Garand. Always check the handbooks, regardless.