I use a set of replacement G43 springs in my G41 shooter. I bought a set of extra springs (G43 but for my G41) from Apfeltor when I picked up a shooter's kit (with springs) for my G43, but several vendors sell them.
If it has the rails for it then that's a cool add on. My own MP43/1 has no rails. I guess just a bit too late production and that idea was already tossed, but if it had a rail I'd have that repro mount for it.
How about posting a pic or two? Otherwise it's a guessing game for those reading this.
The ends/edges of the formed stamped housing meet in the lower center of the rear of the housing and this broken "line" is often confused as being a crack when in fact it is not, but
it is rather how the final...