Damage wise Due to shitreg More bullets will guantee more hits.
So we will go with Bullets>Damage>Accuracy.
You have a 39% Decreased Reload which goes up 81%. So you have 9 Upgrades. This is thinking we push it to max. you will have a M3 with -81% reload. Each pellet takes 1.2~ Seconds. making it around 2 seconds to reload. thats 8 seconds to reload the clip.
Bullets have a cap. it rounds down . to get the most out of the stat you want 79% for 25 bullets. Any higher and its a waste. you need 7 upgrades on that to maximise it.
that leaves you with 3 upgrades left. Accuracy is meh when it comes to a shotgun so damage outclasses it to ensure you get thoes nice meatshot killers and slightly longer BS kills. and at 108% its fine as it is.
with +15%~ damage you get to around 55% damage which makes each pellet 12.4 damage.
this gives a meatshot a max damage of 310. This supposes you hit the torso and dont hit the head/legs or arms.
Arm damage - 7.8
Leg damage- 6.18
Head Damage- 18.6 (all shots is 465)
Looks fun as hell. if you get in range