If you're looking for the hammerspring, probably no better place than the man himself. He's old fashioned, you will want to call instead of email. You can find his phone number at the top of this page: http://www.quackenbushairguns.com/currently_available.htm
I got lucky and got one of his guns in .375 which shoots the 36 cal round ball really well. Of course it was a plain Jane with the cheap metal trigger guard and the no frills stock. Well I love good looking stocks so I just had to do something with this one. I sent it to my friend Brian back in Upstate NY, the man is a master at his trade so I knew he would do the stock some justice.
I had a 50 Bandit. It was durable as heck , no problems whatever. I did take a few deer but you really had to be careful and only shoot behind the shoulder or through the head. I think it shot a round ball around 700 fps if I remember. I think a round ball is about 150 something grain.