M5 Thread size?

[dave321]

not sure where to post this,

dies anyone know the thread size on the M5 Boobytrp device?

 

[kiwieod]

it looks like 7/16" UNF,but you might want to check

 

[dave321]

well a 10mm bolt screws in ok.
its very difficult to pull the hammer back to set it , it has a very strong spring.
is there a special technique in doing it ?