I draw with 18g, then switch pin to 1/2" 30g for shoulders, pec, and quads. 25g 1" for gluts. I'm injecting daily, 1ml. In short yes.

Insulin pins perfect for chest injections

That's all I use. I use 29g half inch but I only inject in quads and shoulders . And I don't backload . I try to stick with brands that are thin oil and have no problems

I don't back-load... seems like an infection waiting to happen. I just draw with the same needle. Yeah it takes a min but have Some patience. If it's a 29-30 gauge it'll still go in with no problem... don't trust all this backloading stuff, Where do you all put the plunger when backloading??? You don't have 3 hands?

It's fine but backloading makes it way easier to handle I use slins for my shoulders because it's a bit easier to manipulate for me personally.

Dude use the search button. I swear this question gets asked once a week...

Yes they can but if you're dead set on using the slin pins then you need to back load them. Pull out the oils with a regular Gage size (23 or 25) and then pull out the plunger of the slin pin and put the oil in the slin pin. Then replace the plunger and inject as you normally would. My advice is to just stick with a 23 or 25 gage because using slin pins to inject is not practical if you are injecting more than one cc of oil at a time.