I believe part of the bad rap Hi-Points get is because of magazines. If you are using a genuine Hi-Point mag and have a problem with it contact Hi-Point because the lifetime warranty includes the mags as well. Also Hi-Point sells mags to the general public cheaper than the resellers on the net. In my opinion you should avoid Pro-Mags as much as possible. I have not heard of a single person having success with Pro-Mags.
As for interchange information. The 9mm pistol and the 380 pistol use the same magazine. The 995 (9 mm carbine) mags will work in the 9mm pistol but not the other way around. The 40 S&W pistol and the 4095 (40 S&W carbine) mags will interchange. The 45 ACP mags are the same as the 40 S&W.
To purchase magazines visit this site.
http://www.hi-pointfirearms.net/home.htm