The projectiles that the syringe guns shoot out are a bit weird... let me explain.

After a small distance the arrows will not change direction with the arc. In other, less fancy words what I'm trying to say is that the syringes need to have physics similar to the arrow so they wont bounce off their targets.

Giving the current projectiles hitboxes and physics similiar to the crossbow bolts or arrows would likely be very effective. The developers already have an item in the game that changes the properties of melees so that they can act like syringes, it probably wouldn't be too hard to just add the whole syringe thing to a normal arrow and get it to fire out of the syringe guns.

It doesn't help too much to "Just use the rifle instead" because it's so powerful that it not only occasionally harms the target from impact damage, the projectile is so small and fast that hits don't even count, no matter what physics mode you're on, but that's a completely different problem

Please note that I'm not bashing on the freaking mod or anything, I just think that it'd really help if the devs gave the syringes physics like the arrow's so it wouldn't have any problems. The developers of this mod probably already know of this problem and are fixing it, I'm just pointing out a solution that might help.

edit: i forgot to point out that this mod is a masterpiece, sorry.