A sleek rifle, the kind mentioned by Skallagrim.

Assuming that since it's a rifle that it's either a carbine or assault rifle. And if it's an assault rifle it's likely a burst firing rifle.

LeeRoy has popped off two rounds into each of the guards, that's four rounds total. 

I don't know the exact amount of ammunition held in it, if left to my devices it'll be twenty shots total.