When you are shooting alot, especially with a newer gun with a rough barrel, do any of you notice the guns still groups, but alot lower like 2" by the end of a 30 round day? I assume, it has to do with lower velocity due to coppered or leaded barrel.

Picked up a used 300RUM in 700P or tactical, with a Leupold 6X20 VariXIII, bipods, bull barrel, and whole pit for around $1100. Owner said only 20 rounds thru it. Took it to the range Sat., and got 4" groups on the first 5 shots. Disappointed was an understatement. Cleaned with Sweets and it was so coppered up, it took me over half an hour to get out the bulk of it. Guess the previous owner didn't clean out good or know how to break in. So, next 4 rounds was 2.5" higher with around .8 or .9MOA accuracy @100yards. Then next three at 200 yards was 2" groups firing one after the other with no cool down. Don't have a chrony yet, but will in a month to experiment.