I had some of the Big Bore '44's a few years ago. Korean made, 45 cal actually. Powerful for an air rifle, loud also.
They have stepped up the game a fair amount. As Wulf points out above though, most are still around handgun power so understand the limits of them. I think they are great in some instances and would possibly get back into them if they fit for me, but get concerned when people don't understand their power limits.
Check Pyramid Air, they are my go to for air stuff. Rifle, correct scope, air compressor or step up compressor, tank possibly, etc. Can get pricey. However, if you also got some smaller caliber ones it spreads some of that cost out some. Precision pistol is the reason I keep looking back at the PCP concept, they are they way to go there.