I have purchased a Savage No, 4 Mark I with a two-groove barrel. Barrel slug mics 0.315". I have a Lee 7.62 X 39mm mold that is dropping a 0.3135" boolit. Inside diameter of fired cases measure 0.318"
Attempts at shooting the 0.3135 boolits with a GC and 7.0 grains of Bullseye gives a fairly tight group for the first 5-8 rounds. Then it starts to open up some; then there is a key hole, and then there is the "Where did that one go, it is not on the paper". We are talking 50 yards here.
It is obviously an undersized boolit problem. I got some aluminum tape and beagled the mold. With one layer on each side, the mold is dropping a 0.319-0.320 by 0.314-0.315 inch bullet. Have I over-Beagled the mold? If I load the boolits to the point they are just kissing the lands, does anyone see this as a problem. When the boolit starts to swage itself going down the barrel, the average diameter should be right at or slightly less than the measure ID of a fired round. Am I out in left field??