Bullet seating dies typically employ a bullet-seating stem designed for use with jacketed bullets, whether for handgun or rifle cartridges. As such, that portion of these seating-stems contacting the bulletís nose is fashioned so that its long, tapered concave surface contacts the bullet in only one place on the bulletís ogive, providing excellent alignment of jacketed bullets with the center-axis of the cartridge case during bullet seating.
However, this design seating-stem, while well suited to jacketed bullets, is ill suited to cast bullets. The singular contact point of the bullet with the seating-stem results in deformed bullet noses, as cast bullet hardness doesnít withstand the pressures exerted during the seating process when supported in this manner.
How to correct the problem when loading cast bullets? Using a seating stem that properly fits the nose of the cast bullet provides total support for cast bullet nose, instead of only a singular contact point, and thus virtually eliminates deformation of the alloy bullet. In order to obtain this total support from a custom fit seating stem, one either must send a bullet or two to the die manufacturer, or have a machinist custom cut a seating stem with the correct contour for the particular bullet of interest. At least, this is the conventional approach.
A custom fit seating stem is easily and quickly fashioned from your existing seating die parts! Simply disassemble your die, removing the seating stem. Next, thoroughly clean the tapered portion that contacts the nose using either denatured alcohol or acetone and a q-tip type cotton swab. This is to allow total bonding of an epoxy glue compound with the seating stem. Now, with the seating stem removed, spray the entire die with a light coating of WD40, this will prevent the epoxy from adhering to any other part of your dies, except the cleaned, degreased seating stem.
Prior to disassembling your dies you need to prepare a dummy cartridge. Using the cast bullets intended for use, take a fired piece of brass and size it just slightly, only about 1/32Ē down the neck of the case to hold the bullet, then carefully seat the bullet into the case without deforming the nose. Little resistance to seating should be encountered with the brass prepared as described above. Once seated, wipe any bullet lube from the bulletís nose, then grease the entire dummy cartridge with a light but thorough coat of vegetable shortening. Finally, place the dummy cartridge into the proper shell holder installed on a single stage reloading press.
Mix a small amount of two-part five minute epoxy (5 minute epoxy gel is very easy to work with) as per glue manufacturerís instructions, place as much mixed epoxy into the concave tapered portion of the seating stem as it will hold, then reinstall it into your bullet seating die body without the glue dripping out of the cavity in the seating stem, leaving the stem screwed deeply into the die. Now, screw the entire die into your single stage loading press, then slowly raise the ram on the press until gentle contact is made between bullet and the seating stem. Be careful not to shove the bullet further into the case, and to not lose contact between the two once the ram is raised to an extended position. Weight the operating lever of the single-stage press with just enough weight to keep the ram extended and applying gentle and continuous pressure on the bullet and seating stem.
After an appropriate time elapses for curing the epoxy in the cavity of the seating stem, lower the ram of the loading press, and then remove the bullet seating die from your press as well. Then, disassemble your die once again, removing the bullet-seating stem. Trim away any excess epoxy which may have oozed out of the seating stem cavity during this process, clean the die of any excess WD-40, and reassemble the die. Check to see that the seating stem now perfectly matches the contours of the cast bullet of interest and provides the necessary full nose contact. Cast bullets seated with a stem thus altered will exhibit far less bullet run-out than those with a standard, unmodified seating stem when checked with a dial indicator. Additionally, even very soft bullets will be virtually unmarked by the seating stem.