How Much Ammo and What Caliber in a Spam Can

A Spam Can is what a can of communist block ammo is shipped in. They come with a can opener but can be opened with the tip of a flat tipped screw driver and a hammer if you do not have a can opener. Put your foot on the can. The screw driver tip is turned at a 45 degree angle and struck from the side near the tip along the edge of the can. As soon as the screw driver pierces the can only let the tip enter 3/8 of an inch and continue hitting the tip from the side near the tip this will tear the can open very easily .

The number of 7.62X54 bullets in a spam can is about 400

The number of 7.62X39  bullets in a spam can is 640 to 700 rounds

You will know if you have the wrong ammo for the wrong gun by the quantity in a can. A minimal storage amount for a rifle should be 1000 rounds of ammo. The BATF was taking note of 1000 round orders so only by smaller quantities each month until you get what you want. First choice buy from a gun shop and pay cash second choice order ammo one can at a time and do not order again for 30 days into the next calendar month.  

Critical is to have the stripper clips for the caliber you shoot. For 7.62X39 this is a 10 round stripper clip and for 7.62X54 these are 5 found clips  get as many as you can afford.
How to make at home what you need for your gun when the day comes you may no longer be able to buy it American Handbook on Guns Ammo and Freedom