With regard to the 5J: the SSRM-2 is just a weird weapon system in the first place. If you're not using fractional accounting, the minimum investment is 1.5 tons and 1 crit for the weapon and 1 ton and 1 crit for 50 shots, for a weapon that deals 4 damage for 2 heat at the same range as a medium laser. That same humble medium laser is 1 ton, 1 crit, 5 damage, and 3 heat.

The only reasonable use for these tiny SRM systems is for missions where mass, volume, or longevity is a concern... but the medium laser has less mass, less volume, and perfect longevity. The single additional point of heat can be made up for with a heat sink that fits neatly where the ammo would otherwise be, and now you've saved half a ton overall.

Who is this weapon system for?

Edit: I guess the main benefit is if your 'mech is not heat neutral then you save heat on turns that the SSRM doesn't acquire a lock, but if saving 2 heat when you miss is a noticeable benefit I feel like you have other problems. It makes more sense with the larger launchers.