Oddly enough, I was wondering something similar, but with two other gearboxes as my guarder shell cracked where almost all version 2 gearboxes crack. Mind you it was at 400 fps, so if you're not going that high, you'll probably be fine. I've ordered a Systema 7mm and a King Arms 7mm version 2 and as soon as they come in, I'll compare them with my broken Guarder in terms of weight and part thicknesses.
Also, for those who own a DYTAC VLTOR MUR, which charging handle did you use? I have a G&P Navy receiver kit as my donor and planned on using King Arm's metal parts kit.
-Vic
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