ToastedWaffles said: Trigger happy, eh? If anyone knows the name of the Doujin, please leave it here. According to this, it reads "Trigger-happy JAG", then a R or a P, and some kanji.
I'm guessing it's a D as in Jagd-. It's the same prefix as used in Germany's Jagdtiger tank, a much heavier version of their Tiger tank. The kanji after is Momo, the characters name, which also literally means "peach". So, the title should be "Trigger Happy JagdMomo-chan".