I have just read the manufactures report on an FN57 catastrophic failure(2x the powder blow up). I have 40 yrs. experience as a machinist and 40yrs. as a re-loader. After reading the report some interesting things JUMPED out at me! First, I have shot the fn57 and I love the gun! that being said, first thing i see is why the factory cases have a coating. This is due to the small size of the case. the brass on this small diameter case can not expand very far before a rupture(even under min. loads this will cause damage). This means the chamber to brass case fit would have to be a very tight fit. Thus the coating, to slide the ammunition into position for the breach to properly engage! important to keep this in mind. positive they tried without the coating and it lead to closure problems(as they have failure tested this gun). so now the issues for a re-loader, that is of great concern.
1st.The brass is very thin on this case(I understand another manufacture is producing thicker cases, this would be my first step to improve overall safety, and i would only reload these cases) which means as you refire/trim,etc. the case becomes to weak to contain the pressures involved very quickly! If you are reloading these factory cases I would not do very many reloads before i discarded this case, and please don't sell them to an unsuspecting buying!
2nd. The manufactures report states the firing pin will strike the primer without being in the fully locked breach position at a distance of .118, this surprised me as it is almost 1/8 of an inch! again, this comes back to the coating issue, obviously they want that breach fully closed before a firing pin strike! so if you reload and say you maybe don't get the overall cartridge length right(definitely don't want this rounds lead to contact the bore or anything like that), maybe a primer doesn't seat etc. you could get an over pressure condition very quickly, and guess what, the breach may not be fully locked! Understand, the firing pin striking at .118 before full closure does not mean the gun is unsafe in any way! just that you have to be careful, to reload correctly and INTELLIGENTLY!
my suggestions. reloading for target practice, use the min. loads( I do this all the time in most of my reloads), do you really need a max. load at the target range?
Carefully check your brass, any significant scratches, or damage, do not fire that round, pull it apart reuse all but the case and primer.
if your reloading factory shells set a strict limit how many times you will reload before you discard the case.
My next step, figure out the coating they are using, any one know?