when reusing a spent shell, and inserting new primer in it, it may work, but it may not. sometimes the head becomes concave from repeated use since there is no back pressure of firing an actual load, and can give false readings, such as not firing even if there is sufficient firing pin protrusion and energy to the firing pin.
That is the benefit of the Brownells test kit. I have had one for 40 years.
other methods work. I choose this one.

Brian
LTC, USA Ret.
NRA Patron Member
AHFGCA Life Member
USPSA Life Member