One of my Players asked me about creating a Custom Gun(p.160) with Special Ammunition causing more stress then Normal Guns.

Looking at the Dr.Blitzmann write up he uses a Gadget that causes +2 Stress on a successful hit(Upgrade Enhancement)
It also has a Drawback that it does not work on  well insulated Targets.

Should I also add a Drawback to Custom Gun using Upgrade to cause extra Stress(Without one 3 stress boxes is very Powerful maybe a little to Powerful)

What drawbacks could be used to offset the Munchkinism of the Weapon.

I have only had one idea so far,Can only be fired once every other Turn because the ammo has to be loaded after every Shoot.

Any other Ideas.
Or is it Okay to deal 3 Levels of Stress every Turn

I'd limit things to a +2.  It takes Martial Artists multiple stunts to get to the point of being able to boost their stress, and that should be regarded as a guideline.

That said, it's not really all that bad; stress tracks in SOTC are very long and while he'll clear a room of minions real quick, taking down a boss should still take some work.

Excellent THX for the advice.