Which seating stem?

[Sarge]

Loading 9mm on a 550. Did some routine maintenance tonight and noticed something with my seating die. I switched from MG 124's (RN) to precision moly 147's(FP) a while back. When I took my seating die apart I noticed a black ring where the FP's are touching inside the seating stem. The stem was in the RN configuration. I flipped it to the SWC configuration and the FP fits nicely against the stem. Should I use the SWC end of the stem for FP's? Or stick with the RN end? I had never thought about changing the stem before since I thought it was pretty much for SWC bullets only.

Thanks much.

[kevin c]

I'll offer my personal observations/preferences:

What I want is for the seating stem to hold the bullet well as it's being seated. I find jacketed RN bullets or similar configurations can tilt in the stem if the bullet ogive is not in circumferential contact with the rim of the seating stem. That means the bullet tip (meplat) shouldn't touch the stem's base, so I use the RN stem for RN bullets in 9mm. For the big fat 40's and 45's, either stem works so long as the point of contact is the rim of the stem. Jacketed FP's or JHP's (which work the same way), are very uniform all around, and the flat end makes secure contact with the stem, so they seat pretty well with either ogive or tip contact with the stem.

Cast bullets may have mold lines or other irregularities on the bullet profile or tip that are not ironed out by the sizing die that will contact the seating die. That usually doesn't affect accuracy much for our purposes, but might increae the range of OAL's you get.

The ammo might be a bit more uniform, matching the bullet to the seating stem this way, but more practically, I do it because I don't want the bullet to tilt in the press and jam it up. It seems to be an issue mostly with pointy bullets like the 9mm 115gr.

YMMV,

KC

Edited October 22, 2009 by kevin c

[BMartens]

Sounds to simple but, use the one that best fits the bullet. Most set ups give you two choices [as noted, RN and SWC] so go with the best fit.

If your FP bullet doesn't reach the top of you SWC stem then it doesn't matter, your seating on the body of the bullet and not the nose.

The one that seats the bullet straight and gives the most consistent OAL results is the way to go.

[Sarge]

Since I did not get the usual speedy response last night I loaded some with the SWC end and found that it left a nipple on the end of the bullet because of the hole in the center of the stem. This of course made the actual oal a little hard to figure out. I went back to the RN end.