I sent you a private message, regarding my serious concerns about what you have been doing, for, if things were normal, you would not be experiencing such deformed brass from you chambers. YOU NEED TO SERIOUSLY DETERMINE WHY THIS "PROBLEM," AS YOU CALL IT, IS HAPPENING, AND CORRECT IT. IT COULD BE A SIGN THAT DANGER IS LURKING. Cordite 37 250 max. means that original load intended was 37 gr. cordite, 250 grain bullet MAXIMUM, and not larger cordite charge and not heavier bullet! However, the 37 gr. cordite does not convert directly to any modern day nitro powder, so you cannot simply use 37 gr. of any modern nitro powder, so don't do that. You need to use only a percentage of the 37 gr. cordite, using a specific modern powder, with only a 250 gr. bullet; not heavier. YOU SERIOUSLY NEED TO GET AND USE A BOOK FOR SUCH INFORMATION, SUCH AS LOADING FOR BRITISH DOUBLE RIFLES, BY GRAME WRIGHT. However, first determine why you have been getting such deformed brass, and correct that problem; it could mean something is seriously wrong.