0.3 mL versus 0.5 mL versus 1 mL barrels: resolution matters

Two sentences on 0.3 ml versus 0.5 ml and then I will stop, because the rest is speculation and the thread is better without mine.

What is documented is narrow. What is inferred from it is broad. The gap between them is where every argument here lives.

Post #19 and I disagree about the size of the effect, not about the direction.

A detachable luer needle plus hub can retain enough volume to matter. Whether it matters to you depends on your dose, and the arithmetic is worth doing once.

That is the honest state of it as of this week.

0.3 ml versus 0.5 ml is a good example of a question where the honest answer is boring and the interesting answers are unsupported. I would go with boring.

Graduation spacing is worth checking before you buy rather than after. Some 1 mL barrels are marked every two units and some every one, and that changes what doses you can read.

Someone will know this better than I do and I hope they say so.

This follows post #61 rather than contradicting it.

Fixed versus detachable needles: insulin syringes usually have fixed needles (no dead volume loss to the hub). Luer-lock syringes use detachable needles (more dead volume). Fixed needles are preferred for small doses.

The honest answer is that it depends, and here is what it depends on.

What I would check first on 0.3 ml versus 0.5 ml is whether the thing being measured moved or whether the way of measuring it moved. Those look identical in a graph.

Answering the question post #90 raises rather than the one it answers.

On 0.3 ml versus 0.5 ml I would separate what is worth knowing from what is worth acting on. The first list is long and the second is short, and conflating them is how threads get heated.

Post #101 describes the usual case. This is about the unusual one.

Fixed versus detachable needles: insulin syringes usually have fixed needles (no dead volume loss to the hub). Luer-lock syringes use detachable needles (more dead volume). Fixed needles are preferred for small doses.

I would treat that as a working assumption and revisit it.

The failure mode on 0.3 ml versus 0.5 ml is boring rather than dramatic. It is almost always the step everyone assumes was done correctly because it is too simple to get wrong.