Looking to purchase a new/used handgun

Good questions

I am experienced as far have I have shot a gun I do go to the range often. I already own a .40 S&W Sigma. But I wouldnt trust my life with it due to the fact thats its inaccurate as fuck.

I would like a to stay semi-auto.

As far as caliber Im thinking 9mm because of the cost of shooting it at the range. But for the money I save in gaining experiance with the firearm, I lose the stopping power of a large caliber round (.40, .45 etc etc).

I have shot a Sig before and I was very very impressed with its accuracy and balance but the price is just a little high.

Based on these questions Im really going to start looking into the Glock and the used sig.

Thanks for the help!!