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Looks like one of your barrels is a little higher than the majority, most .303 barrels are very worn in the throat I bought the fattest mould I could get for that reason

The bullet nose diameter is .305" the lead is very soft so will jam in the rifling very easily, seat the bullet just off the rifling is the best option.

I don't recommend shooting these bullets faster than 1900fps most feed back I get is that 27.00gr 2206H is the load to start with
look for accuracy not velocity with cast bullets the HP will expand...