I am talking about the shell stop mechanism as a whole. Taking the shell stop out of the 940 and putting it into a 930. I imagine that the outer part of the bolt release that screws on is to give a bigger finger area and to address the over-travel/ shell dump issue on the 930.I have both a 930 and 940. It doesn't 'appear' that the 940 BR will work on the 930. The 940 BR has a hole in the center to attach the BR. The 930 looks to be mounted different. Not sure if it screws off or not. But I would say it isn't interchangeable. GG&G sells one for the 930 that looks 'similar' to the 940 BR, i.e., it is elongated. It is not just a bolt on part. Some detailed disassembly/reassembly is involved. I installed a larger BR on the 930 from the Or3gun website and it works great.