I guarantee that I can push 1cc out of a 29g insulin syringe MUCH FASTER than anyone else can push 1cc through a 3ML 25g.
Its not even close.
Matter of fact, less than an hour ago. I had started an injection for a friend, and I stopped 10% of the way through 3cc injection because I was frustrated with the amount of pressure required on the plunger and the amount of time it would require.
So 10% in, I stop, load the remaining oil into 29g slin pins, and did the injection that way. SOO much easier. Its night and day.
As a matter of fact, I have yet to meet a BB who has tried slin pins....and chosen to stick with larger needles. The only people who I have met who still believe the harpoons are better (there are many ppl who do; and my arguments against slin pins were documented years ago...on this very site) have never actually tried slin pins. They just assume by logic that it would take more time for the injection.; which just hasnt proven true IME.
Im pretty sure Millard made the switch and uses slins as well FWIW.