Mike, try them in a different gun. I was given some of the Winchester Featherweights to try and used them in light English guns without a problem. Greenbat Powder. that brings back memories. I never knew it had been exported. Was it the pale purple powder by Greenwood & Batley? Only problem I had once with opening problems was with some French FOB stuff that has soft primers which allowed the firing pin to pierce through making it difficult to open. Lagopus.....