Variations in seating depth

[Garrett]

Although I have been reloading pistol ammo for over 15 years, I have recently revisited my (only somewhat successful) attempts at loading rifle ammo.

I have noticed what I think as an excessive amount of variation in seating depth, and I'm a little curious as to why.

Bullets are 62 gr. FMJ-BT bullets that I bought from Graf & Sons 5 or 6 years ago. The bullets bear the Graf name, so I'm not sure who the actual manufacturer is. While it is possible that the difference may be related to bullet selection, I would think the make of seating die and press would have some effect on finished OAL.

I am not using a "competition" seating die. However, while these make precise adjustments easier, the physical method of seating is no different than that of a standard die.

After seeing the difference in OAL I tried some variations and then measured a couple of factory loads to compare mine against. My findings were as follows, with a sample size of 20 for each lot.

Horniday seating die on Dillon XL-650

Ave OAL: 2.242"

max-min: .023"

SD: .007

RCBS seating die on Dillon XL-650

Ave OAL: 2.256"

max-min:.063"

SD:.012

RCBS seating die on Rock Chucker

Ave OAL: 2.250"

max-min:.015

SD:.005

Winchester 55gr. FMJ factory load USA223R1

Ave OAL: 2.206

max-min:.011"

SD:.009

Black Hills 69 gr. SMK factory load - Red Box

Ave OAL: 2.246"

max-min:.009"

SD:.003

Maybe it's just that the progressive press has a harder time holding the same tolerances that a single-stage press can. Or maybe I need to check the Horniday die on the single-stage press. Or maybe a different bullet would give better result. Maybe I'm making a big deal over nothing, as at least one of my loads was better than the "blaster" factory ammo, and nearly as consistent as the more expensive "target" ammo.

Any thoughts? Suggestions?

Edited April 5, 2009 by Garrett

[Dan Sierpina]

When using the 650, do you have the shell plate full? Only having the seating station being used allows some flex of the shell plate.

The other thing, seating dies contact the bullet on the ogive, not the point. Check the length using a Stony Point tool or a tool from Sinclair International. The depth on the ogive will be closer.

The 62 fmj bullet isn't going to give you fantastic accuracy, it's not a match bullet, and they are coming out of multiple dies, then mixed in boxes.

[Larry White]

Also make sure your shell plate is as tight as you can get it and still let the machine cycle. I dont think a .01something is that big of a deal, less measureing, more shooting called for here.----------Larry