injection with a one inch is okay. when your injecting you don't need to put the needle all the way in. that's any needle bro. most time when im injecting my pt's with im or sq I don't push the needle in all the way its not necessary to bottom out.
edit= slin pins come with the needle on them. some sq are premade also, but to say doing a sq with anything but a slin pin in wrong, is incorrect. it is dose dependent. I give sq regularly in the hospital with larger syringes. slin pins hold 1 ml max.