Building or Buying Monster!

I'm in the market for a big bore pcp. Something like the Texan 50, 457 or 35(with similar performance specs). However, I'd like to find one, build one, or have one built with a bolt action. Preferably bottom fed magazine (10 round capacity) , but a revolving magazine (5 round capacity) would be my second choice. 

Is there anything like that on the market? Or is it possible to build it?
 
Your air tank is going to be huge

Texan .45 see performance change from its 3rd shot onward, so I'd you want to shoot rapid, you will basically need to be carrying a scuba tank with you



From my understanding, there isn't anything like what you've described in the market for now.

You're right. I didn't take that into consideration. Im primarily going to be using it to hunt. I really won't need more than 3 to 5 shots (and that's pushing the shot count very hard).