A Suggested Alternative
This is not secret but, steel mandrels of "Pop" type pulled rivets generally work better - for (at least) a couple of reasons.
1. They are made of a higher strength steel - not much of a chance at pulling the "head" off the stem, unlike a low grade alloy commercial nail.
2. Since they are designed with a "frangible" stem that breaks (repeatedly) at a pre-determined force (much higher than a nail), you get good repeatability of the quality of the dimples being developed, especially with thicker skins (.025 & .032).
3. If you have any Pop rivets already in your inventory - you're good to go without leaving the shop.
If you elect to go this route, you may need to slightly enlarge the holes in the dies to accept the nearest rivet mandrel size available to you.
YMMV
FWIW - Many moons ago I contacted a well known pull rivet manufacturer and inquired as to whether I might be able to buy the stems only, in bulk, and then resell or give them away to VAFer's. No Joy - they didn't even want to discuss it - to much projected liability I guess. Oh well.
HFS