Hi-cappa 4.5 firing full auto
 

i don't have much experience with Hi-cappa's trying to fix this for a friend of mine. He replaced the grip and after he did that the gun fire's in full auto with out pulling the trigger. sometimes the hammer wont cock back, and the slide will get stuck on the hammer it self.

Any suggestions as to what the problem could be?

I think the finger spring have some problem. The parts H51-69 , check it out
http://www.tokyo-model.com.hk/ecshop...1432167860.jpg

I had that problem with mine. It turned out to be the leaf spring wasn't seated properly. Thanks to "illusion" it was a simple fix.