Take a look at the front detent pin under the barrel. if it has sharp edges, it can hinder cylinder release by binding on the recess in the front of the ejector rod. I've had this happen a couple of times. To remedy it, I removed the pin and lightly polished the face of it. I also checked the ejector rod recess and lightly polished the sharp edge. I emphasize: LIGHTLY polish if it turns out not to be one of the other possibilities listed here. Also check the rear end of the center pin that locks into the cylinder lock/release hole in the blast shield/breach face. The shoulder on the rear of the center pin can be slightly polished as well.

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Dave Frost