You cannot cast skirted pellets, but bullet in 22 caliber are quite easy to cast.
You'll have to get one of the high powered airguns with compressed air tanks, to be able to shoot cast bullets, and I would reccomend a 25 caliber or larger.
If you want to keep the price down, yet be able to take down fair sized small game, I strongly reccomend the RWS 22 caliber side lever and their pointed field pellets. I have one and it will shoot completely through a large skunk. Grouse get a half inch hold knocked through them and ground squirrels die instantly with good chest hits, or head/spine. If you should need to drive off a coyote or ferral dog, on in the ribs is pretty sure poison, though you can expect a run, which means you don't have to burry. Not all bad. The pellest are expensive, but deadly and accurate to 100 yards, and you can buy the gun and probably a lifetime supply of pellsts for the price of a high power airgun and what it takes to make it run.
I've had nothing but sour taste for all break barel pellet rifles. the barrels all wobble so a scope mounted on the main body is never aligned with the flopping barrel. If your eyes are good enough for the iron sights they aren't too bad for ranges to 30 to 50 yards.