My friend has a hammer extension, he uses with his muzzleloader, .243, 7mm mag, and 45-70, he's never had a problem. Mine never misfired with the muzzleloader, but it did with the 7mm-08. Just out of curiosity, those of you that have had misfires, what style of extension did you have? Mine attached to the hammer at the end of the extension, my friends attaches to the hammer in the middle of the hammer extension, I wonder if this would make a difference?