27g 1 1/4

Will 27 g 1 1/4 pins work for glutes? Or is the gage to small?

You'll have to push pretty hard to get any oil through. 23g is pretty standard. Also go up to 1.5 inches if your gonna inject in your arse.

Is 1 1/4 not long enough? What's happens to gear if you don't go deep enough? Is it waisted or does it still make its way to muscle

I'd say you could be wasting some. If you are really lean the 1.25 could work but the deeper the better. If you use a different pin site you could go shorter then the recommended1.5 but again it depends on leanness. Standard for glutes is 1.5 tho.

depends how lean you are. i use 25g 1 inch for every place.

I'm 15% body fat and have been using 1" but sometimes gear will dribble out

Then that's your answer. Go longer so it goes deeper. And be sure you eat clean so you can lean up further. 10-12 % IMO.