Cap total particles on screen by group?

I’ve got several particle systems which spawn “odds and ends”, small mesh particles which do a simple physics simulation and then come to rest. When the gun fires, a shell casing is spawned. When an enemy is hit, a randomized spray of nuts and bolts fly off of him.

I’ve capped the lifetime on these at 50s, and this actually works quite well. Particles come into existence, look cool strewn about the battlefield, and eventually die inconspicuously.

The problem occurs when certain attacks are fired. Namely, I have an attack where the player spins his gun in a circle and all enemies in range take damage repeatedly like they were being shot. This is fine for 2 or 3 enemies. But if I do it with 10-15 enemies in radius, having them ALL spraying nuts and bolts while the gun sprays shell casings… Well, suddenly I get framerate drops.

I’m wondering if there’s a way to cap the total number of particles just in this group (of tiny physics-driven meshes) so that once we reach the cap, each new one spawned kills the oldest of the set, to prevent the count from getting ludicrously high in these edge circumstances.

Capping the total number for each system would work, of course, but it’s be less elegant, as the real problem is the aggregate number of these (CPU) particles from all systems, not the total number each system spawns taken in a vacuum.

EDIT: Actually, capping the total number with Max Draw count doesn’t do anything on mesh particles…? I can set the max draw count to 1, and they still spray out like crazy.