Concerning the Polish 7.62x54r ammo question: I have shot several thousand rounds of it through my PKM machine gun without a single misfire. The accuracy has pleasantly surprised me as well. As yet, I have shot little of it through my MN [Mosin Nagant] bolt rifles but have not had any problems there so far. Czech, Russian, Polish, Chinese have all been fine. The only 54r ammo that has been a consistent problem is the Albanian. Crimp is not done properly making it nearly impossible to load into Russian belts and feed into my PKM and SG-43 Goryunov. It will work in the bolt guns but not as well as the others do. Anybody wants some, I certainly have plenty to get rid of!!
I treat ALL surplus 54r as corrosive. For some reason, it does NOT all seem to be corrosive in the same way – I have no idea why. Like you, I consider ammo that is mildly corrosive like being a little pregnant. Corrosive primer chemistry allegedly is less sensitive to very low temperatures which is one reason the Russians continue to use it. Same for long term stability. I have some 54r that has primer problems and also some newer (mid fifties) 8mm FN with the same issue – however both appear to have been very poorly stored and corroded, many rounds having bullets so rusted that I will not shoot them in a good barrel. Upon disassembling them, many even have rust mixed in with the powder. I make display dummies out of a number of the bad rounds and find that some of the primers are okay, some completely dead and some that are very weak or merely make a little smoke and don’t even “pop”. I have NEVER had an issue of duds from a well-sealed can, some dating to the early 1930s! I shoot a lot of old, corrosive, cheap ammo and have amazingly little trouble. Your experience may vary.
Storage of ammo is important. Dry, moderate temperatures are best. I leave mine in the spam cans until the shooting season begins then open and immediately put in military ammo cans with good gaskets. If it is to be belted, I load the belts then put them in ammo cans. Store in my garage out of direct sunlight. Have had zero problems to date.
Cleaning after corrosive ammo. It depends on how much moisture the gun is exposed to how quickly it needs cleaned. In my safes with “Golden Rod” heaters I have no trouble for one to two weeks. Sitting in the garage in Ohio’s notorious humidity, a few days seems the maximum. Of course, chrome lined barrels are far less of a problem. If it may be a while before I can get my guns cleaned, I douse them in WD-40 (I buy it by the gallon can – cheaper). To clean, I use one of several different methods. Hot soapy water is probably best. Immerse the muzzle in a bucket of it and brush in such a way as to really wash it out. If the water is hot enough, the gun will flash dry on it’s own. Apply oil to all parts exposed to the water as it removes all of the oil residue and rust is a certainty! I prefer LSA (available from Sarco, $6.95 per quart) or CLP (which I pick up at Knob Creek for about $10 per quart). If the hot soapy water is a problem I use Hoppe’s Copper Solvent which contains ammonia, followed by Hoppe’s #9 [bore cleaning solution], then oil. The ammonia helps rinse away the corrosive salts, not to mention removes some copper fouling. Most important, IMHO, is to inspect the gun every couple of days after cleaning and again a week or two later to make sure that you did not miss some odd spot and rust is developing. While I admit cleaning a PKM, Goryunov or AK gas system after corrosive ammo is a bit of a pain, the [low] price of the ammo certainly justifies it. Remember, when these guns were new and being used by the military, corrosive was the only kind of ammo available! A note on Hoppe’s #9 – the older formula contained Benzene which worked very well at removing corrosive residue. Trouble is, the stuff is hazardous so it is not in the current formula. Hoppes still will clean a gun of corrosive residue but more effort is required! Same for some WWII / Korea era GI bore cleaner.
Cheap but reliable ammo in sealed military cans is great to have for a SHTF stash. A couple cans of it opened and stored in .30 or .50 caliber gasketed ammo cans allows you to shoot some for practice and to prove that it works. Remember that occasionally a spam can leaks and the ammo inside will be junk. By opening one or two, you know that at least some is good. It is also possible to leak check a can by submerging in water and squeezing it hard enough to force out some air – making bubbles. I have found so few bad ones I don’t bother.
A bit off subject – Guatemalan .5.56mm in battle packs sometimes has a problem. They have some nasty bug down there that bores through the plastic [allowing moisture to enter and] and causes corrosion. Good ammo but I suggest you put it in GI ammo cans to be safe. No, I haven’t found any live bugs yet! – Mike