Is the LR 300 horrible or am I?

I just got roam raided while I was out and about and the guy inside my base had a Thompson and was campaign my drop down. In a close range fight I shot him 4 times. He was road sign. I was full metal. How on earth does a gun from world war 2 outclass a modern rifle?!? Am I trash or is this gun actually so fucking bad?!?!