My good friend and that I made some metal targets just like these out of 10mm delicate metal and so they lasted lower than 15minutes earlier than they had been utterly stuffed with holes. And that was at 100m.
What did you chop them out with? If it was with fuel, that may in all probability have ruined the mood, given how small they’re. If it was with instruments, you’d positively have recognized if it was hardened as a result of it could have been a complete ache within the ass.