a guy of my former team became something like"our jolly fellow for everything" because he knew all the guns. he just took them apart, looked at it all, cleaned here, did some oil there, changed this or that and got the thing together again. themn it was always some kinda holy moment, it was great!!! he mostly got the best out of our guns. only by taking a good look and understanding of what he saw. this guy even built his own e-mag and e-cocker sets(hes educated in this electronic stuff).
so he was a "gun tech" without certificate.