[Unclenick]

Interesting case design. The step is a positive stop for bullet seating. The thickened brass at the body should tolerate higher pressure without blowing out. Note how thick the web is. Probably used a stiff charge of fairly fast powder. I don't know if they were wanting to prevent a target level load from having a lot of extra space in the case, or if they meant it to be fired in a fast full auto weapon without bulging and affecting extraction. Oddly expensive approach unless brass is cheap there. Obviously, standard load data would not apply to it.

You always have to inspect cases. I once got a freshly fired LC .30-06 case (this was from a DCM match back in the days when ammo was issued) that felt odd. I weighed it and it was 35 grains heavier than the average. Looking inside, there was a dark area around the flash hole. I applied a dental pick and retrieved a 35 grain slug of lead. It was apparently part of a bullet core that fell in at the factory. This was in government loaded ammo. QuickLOAD suggests it would have raised pressure about 10%. Nowhere near proof pressure, but not something I wanted in my handloads.