The following guide was made by me and written in my words so don't call me leecher for this but however, I didn't invent this. I don't know if this has been posted before or not but it never hurts to post something useful that is working again and I believe it hasn't posted like this way. If you know this, well good for you but lots of people don't.
What you need:
A Bypass (MPGH Public Hack comes with the bypass)
MHS (Memory Hacking Software)
Q) Is this unlimited Ammo?
A) NO, there is no such thing like that.
Q) Will this work for other gun?
A) NO, it will only work for your default gun. If you change weapons then it won't work to that weapon.
Q) Will this still work if I leave the game?
A) YES, it will still work until you close Combat Arms.
Q) If I die, will it work?
A) Yes, it will still work.
Q) If I change my default weapon, will it still work?
A) I believe NO, it will only work for your default weapon that you scanned.
Q) Everyone in the game is frozen after I tried scanned it and locked it.
A) That means, you have died at least once when you followed this tutorial. Find a safe place to do this at.
Q) My CA closed when I did this.
A) Then, I don't think it works for guns with many bullets.
Q) If I close MHS, will this still work?
A) No, it won't.
Q) When I shoot bullets, the person didn't die.
A) if you shoot people from far away and scoped then it won't kill them, so this is only good for mid-combat battles instead of scoping and sniping.