Surplus military bolt guns and SKS autoloaders have a fixed box magazine. Cartridges are loaded into this non-removable magazine either singly or by use of a stripper clip. The stripper is a stamped metal strip that holds the correct number of rounds of ammo in alignment. The assembled stripper clip is placed in a groove on the bolt carrier, and the cartridges are pressed off of the stripper and into the magazine with the thumb. Get plenty of these, and test their function.
Some strippers have a rough finish.
A little cold paraffin applied with a stiff toothbrush to the bearing surfaces which contact the cartidge rim will fill the pores and smooth stripping. Get pouches or bandoliers that fit these loaded stripper clips or you will have loose rounds in your pocket. As of January '99, surplus military ammunition in 5.56 NATO, 5.45x39, 7.62x39, 30'06, and 7.62 NATO can be purchased in case lot quantities. Some imported ammunition may have the older corrosive type primer. This is not a problem as long as proper weapon cleaning procedures are followed.