For plinking, I would think you could find bullets cheaper than the LRs suitable for the .450 Bushmaster.
The 450 Bushmaster LRs appear to be 250 grains, and the LC LRs appear to be 225 grains. Seating depth and gas gun timing would need to be considered. The LC LRs have two cannelures (from the pics), which may not work for your application, or you would crimp not in the cannelure, such as with a Lee factory crimp die.
I suspect also that the 450 Bushmaster LRs are constructed stronger and designed to expand appropriately at the designed velocities of 450 Bushmaster (ca. 2200), whereas the LC LRs would be designed to expand at substantially lower velocities (check Hornady LR spec. ammo velocities).
Can it be done? I don't know for sure.
Do you have data for the 225 grain LC LRs for the .450 Bushmaster?
Will the 225 grain LC LR bullets stay together at the increased velocity and rotational speed that you should expect out of the .450 Bushmaster? Call Hornady and ask.
Are you prepared to mess around with seating depth and powder charges to get feeding and reliable cycling with the lighter bullets?
Someone has probably tried it and written about it on the internet, but these are just some of the things that come to mind.