I had (emphasis on the 'had') a Pedersoli Le Page in .36" cal that kept blowing the hammer back. It was fitted with an aftermarket copper Beryllium Nipple and I drilled a 1mm cross hole in the nipple cone a la Slix Shot hoping this would sort the problem. It was an absolute b*st*rd to drill and made no difference whatsoever! I eventually replaced the mainspring and all was well. Incidentally a previous owner had polished (and lightened) the original mainspring thinking it would help with accuracy, which maybe it did for a while?