Several months ago I was seating some 175 grain Sierra Match Kings into some 308 Winchester cases and when I measured the overall case length I was getting vastly different readings from my calipers. I would set one, adjust my seating die to 2.80 and the next one would be off. I’d readjust my die, seat the next bullet and it would be off and I’d fight it into spec. This vicious circle would continue until all of my cartridges were exactly the same overall length. What I didn’t realize at the time is how most HPBT bullets like the SMK is manufactured; a jacket is extruded over a lead core and the hollowpoint is what is left at the Meplat (also referred to as the tip of the bullet). This hollowpoint is not intended for expansion, it’s a hangover from the manufacturing process and not perfectly even on the end. So measuring off of this imperfect point was actually causing me to inconsistently seat my bullets! Here is a close up picture of the Meplat of 3 Sierra Match King bullets where you can see, in spite of the poor photo, how uneven the hollowpoint actually is.
Not only was I creating inconsistent cartridges, I was also spending an exhausting amount of time chasing the seating depth around for no good reason. Some handloaders work around this problem by trimming each and every bullet with a Meplat trimmer which may also improve accuracy, but I don’t think the effort/benefit ratio is worth it for me. That’s when I decided to try out a device called a bullet comparator which eliminates this problem by measuring off of the “Ogive” of the bullet rather than the end of it.
Next I thought I’d measure a sampling of my “perfectly” seated handloads so I procured a bullet comparator from Hornady and quickly had it mounted on my calipers to began testing only to discover that for all my efforts I had created poor cartridges. Even though the OAL was perfect, measuring off of the Ogive showed a large variation in seating depth which can lead to inconsistent results downrange. Once I started using the bullet comparator when taking OAL measurements to set my seating die I soon realized that I was already making great handloads, I just had to keep my hands off of it and they’d all be seated at the same depth. This epiphany has enabled me to crank out my handloads in a much shorter period of time than before I started using the comparator to verify my bullet seating depths and is now a permanent addition to my handloading workflow.