I had to cut the choate spring down to the length of the shorter Mossberg factory spring...yes, it was way too long. The factory spring is not too weak even with the extension on. I am just keeping the choate spring as a spare.i'm also getting a 930 soon in the coming weeks (when it arrives at my ffl); its the one with the 28/18.5" barrel combo
i'll be looking for an extension; is the choate spring that bad? have you tried cutting a few rings off? does the factory spring still work with an extension or is the spring force way too weak because of the short length?