Low dead space syringes I found available in 2.5-3ml as well, some long time ago, hence the exipration date on them. But the Excel or whatever the brand is must still make them.
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As for the insulin ones, I use the 27G for gear, I used to back load them, but found the ones I use now have a strong anough needle that does not get blunt from the stopper of the vials. I use Unisharp ones, easy to buy in bulk directly from the manufacturer.