Accurized Micrometer Bullet Seating Die | .243 (6mm)

Tangent and secant describe two bullet nose profiles. A tangent ogive blends into the bearing surface; a secant meets it at a sharper angle. A stem cut for one rides the other on a point rather than a band, and that point moves from round to round. Both stems ship with the die, tangent at 13° and secant at 10°, cut for your bullet diameter, so you match the stem to the bullet instead of settling for whichever one came in the box.

Color the nose of a bullet with a marker, then seat it lightly against each stem in turn and look at where the ink is rubbed away. Whichever stem marks lower on the ogive, with more surface in contact, is the one for that bullet. It takes a minute and it settles the question for that bullet permanently.

The ogive is the most dimensionally consistent surface on a bullet. The tip is the least. Contacting low on the ogive, near the bearing surface, means the die indexes off the part that doesn't vary, and it leaves the nose unmarked, which matters on thin-jacketed high-BC bullets. It shows up on your comparator as tighter base-to-ogive spread.

As the case rises, a sprung sleeve captures it and holds it concentric with the seating stem before the bullet is pushed. The bullet enters the neck square rather than slightly cocked, which is the mechanical cause of runout. You get straighter ammunition without adding a concentricity step to your process.

Seat a dummy round — no powder, no primer — and measure it base to ogive with a comparator. Every click moves seating depth 0.001", so the difference between what you measured and what you want is a click count rather than a guess. Once the round measures where you want it, re-zero the micrometer at that setting. From then on the number on the scale is that load, and you can move off it and come back to it.

Standard 7/8"–14 thread, so it fits any press with a 7/8"–14 die station — the XL750, RL550, RL1100, Super 1050, CP2000 and BL550, and effectively every other brand. Two presses have a station note: on the XL750 the die will not run in station 4, where it fouls the powder measure. Use station 5, or station 3 if you are crimping. On the RL550 station 3 is the intended location; in station 4 the threads can rub the ejector wire, so it only works there on taller cartridges that don't need the die threaded down to the shellplate. The Square Deal B is the one press it does not fit: it uses Dillon's own SDB dies and loads handgun calibers only.

No. The lock ring is cut to seat correctly on single-stage presses as well as on Dillon progressives, so the same die and the same lock ring move between a 1050 on the bench and a single stage used for load development. It also works on free-float presses such as the Forster Co-Ax and the Short Action Customs Nexus.

No. The die is built for rifle-profile projectiles only, and the seating stems are cut for rifle ogives. It is not intended for handgun bullet profiles.

Order the conversion kit for that diameter. It carries both stem profiles and the diameter-specific case centering sleeve, and the die body doesn't change. Swap, re-zero, load. Covering all six this way costs a fraction of six dedicated micrometer dies.

Order by bullet diameter rather than by cartridge.

Complete die: .224 40021 · .243 40022 · .264 40023 · .284 40024 · .308 40025 · .338 40026

Conversion kit: .224 40027 · .243 40028 · .264 40029 · .284 40030 · .308 40031 · .338 40032

If you are not sure which diameter your cartridge uses, the coverage table on this page lists the common ones.

It covers a bullet diameter rather than one cartridge. Most premium seating dies are cut for a single cartridge, so three cartridges means three dies, three boxes and three setups. This one moves to the next diameter in the family with a conversion kit, and both ogive stems and the spring-loaded centering sleeve are in the box rather than sold as accessories. On a bench that loads more than one cartridge the arithmetic is different from the shelf price.

On most dies the scale ends up wherever the threads leave it. Here the graduated cylinder turns independently of the adjustment stem: set your depth, then spin the scale to face the front of the press. You read your own setting without leaning over the toolhead.