I think theres some wierdness related to the current plasma rifle that is turning a lot of players off to using it.
Number 1 it has 72 “maximum shots” and it “Doesnt reload”
So up front plasma weapons need to reload … im not sure where it came from that you thought they had a full tank in one go … but plasma wepaons need to replace cooling rods to help prevent them from overheating. they are a slow reload so probably similar to the bolter.
They have semi auto and semi auto burst(2)
each clip holds 40 rounds of cooling.
Thier main benefit as a weapon is thier penetration. so another good way of thinking about this is, when a player chooses the plasma rifle they are saying “im going to shoot this at the enemy tin cans, and maybe some of the troublesome flak enemies, but i dont have enough fire rate and self loathing to fire this at hordes and make it blow up.”
This weapon should be the best weapon in the sharpshooters arcenal for killing Ravagers and crushers, and if we ever get a heavily armored monstrosity. There is no other gun presently in the game that should have higher damage per shot and better damage percentage punch through to heavily armored targets. I gave a melee breakdown on the thunder hammer’s role and this should be the ranged equivalent. This thing should probably punch through for 60-75% damage against Carapce enemies uncharged and charged should probably do 90% punch through and some bonus base damage. this weapon in trade should overheat easily if burst fired for too long or charge shotted too many times and be inneficient against unyielding and horde type enemies. It should perform averagely against flak enemy profiles.
Dont make the ammo limit what keeps players from using it on crowds make it the slow firing and lower target shoot through. Its ok to make it a little more efficient against medium flak enemies than any other heavy penetration ranged weapon because the sharpshooter (assumadly) should excel at ranged combat.
Another way you could manage it is the higher the heat bar the more cooling it takes from the clip per shot, so a single snap fire is 1/40 a two shot burst is 3/40 and a charged shot is 4-5/40 and the total ammo reserve is actually 120 (2 spare clips is pretty standard issue in 40k) 40 in the clip, and 80 in reserve at full ammo fully loaded.
However, if the user fires again while the gun is still hot the cost in cooling rods goes up, snap shot 2, semi auto 5 charged 6, and if they ever shoot a shot that requires more rods than remain in the chamber it overheats and does damage to them while they reload.
Maybe an audial and visual heat effect could help remind people without looking down at rods and heat bar.