Can't mod it pass 90 but everyone else seems to have it pass 100. I'm level 53 and maxed out on gun nut, can you only mod it pass 100 on pc or something?

What do you mean by pass 90? I am confused. Are you talking about damage? If so get Nuclear Scientist perk.

You need the rifleman perk.

Yeah rifleman ends up doubling the damage with all perk levels on an already pretty powerful weapon

You're probably missing rifleman perks. I have fully modded automatic-armour piercing version of it and it does 190 damage times 2. Pretty sure it's only beaten by a Gauss rifle.

Max out Rifleman, Bloody Mess, and Lone Wanderer. You'll be one-shotting frickin' everything.

Rifleman perkage, and maybe the bloodymess percents might be added to the total damage?

Also that gun makes things too easy lol.