This thread should probably be placed in the "Ask a Weapons Expert" section.

P2K's are purchaseable at the spar complex.

However, you need a 100,000 kills to enter the room that sells it.

Each P2K costs 100,000 gralats, meaning if you want both, you have to spend 200,000 gralats, the cost of the BAR.

From what I have seen, the gun alternates from left to right (or right to left, doesn't matter).

P2K's come with a variety of different skins.

I may be mistaken but some are requirement locked.