I've actually become really good at the game and kinda broke it in a way. Especially in the PVP aspect.
I have the never without one ability card, and my hat protects my head for one headshot, it's basically a helmet and a warning someone is trying to kill me.
I also use slow and steady, and 2 health abilities.
I drink a lot of snake oil, health cures, the game is all about tonics and deadeye, and the right abilities equipped (maxed of course).
For example, I'll go into deadeye mode after i drink a potent snake oil and it'll fortify me, I'll eat about 6-7 headshots i swear while popping everybody charging me and listening to crying rage, getting voted out of lobbies and such. I can't help it that I figured the game out in a cheesy manner.
The upgraded Litchfield is a very good gun to beat the tanky builds, but you must know how to drink your oils, health cures, and dominate deadeye. Lancaster was my go to PVP gun before rockstar updated the Litchfield.
When I run into good players, I bring the explosive rounds out. Best investment in the game although you only get a small sample size. But you can dominate a feud.