my only thing to add to that is twofold:
1. m39s are about 150-300. even the 150 0% finish ones will blow up soda cans at 200 yards. the russian mns will blow up soda cans at 25 yards.
2. HEADSPACE your gun. preferably, do this befor eyou buy. as a shameless plug i do sell headspace gages, but to make up for that plug, if you live near me I will headspace any gun you own for free. if you are a senior member you can also borrow any gage from me for free, just pay shipping.