I believe there’s one of the die makers that will machine up a custom insert but can’t recall who it was. Ideally all being equal then yes you should get the same measurement but only if the seating die insert contacts the ogive at the exact same point. The other big guns all use precision made CNC projectiles so there’s no gains to be had measuring them. I only do this for one rifle (375 Cheytac) because it’s a very time consuming tedious process and this is the only caliber I kill things with at distance. It stands to reason that the brass has been prepared to a similar level of anal retentiveness. When It comes to seating, I will seat long then measure with the gauge, subtract the difference and adjust the micrometer on the die for the final seating depth. It’ll take me the best part of 15-20hrs over the course of a week to point, trim, measure and sort into lots ready for loading. I use the Hoover Meplat Trimmer with a custom body made for the 350gr SMK which I buy in packs of 500. Once uniformed you will have a consistent Meplat to ogive and ready to then sort by bearing surface in. The next step is to uniform the Meplat by either trimming or pointing then trimming.
In order to eliminate this you need to cast the chamber, measure the lands and precision machine a collar for the comparator.
The ogive of a bullet is where it first engages the rifling as we know but why does it vary so much round to round and even bullet to bullet? Unless the gauge & die contact the bullet at exactly the same point when used then you’ll have this problem due to the variations in the bullets profile.
#Forster datum dial crack#
I’ll have a crack at this cause it’s something I’ve spent considerable time getting my head around. It is here that I think if only I had that special comparitor every measurement should be the same. The stage that I am really interested in is that first measurement when I remove the ejector from the bolt and do the testing to find the depth of that projectile and the measurements that I take. I have not found a projectile to be that sensitive yet that this effects the group. As you say then there is the mechanical tolerances of seating esp if you have any sort of compressed load.Īll that is why I leave at least 5 thou tolerance on any measurement if I want 10 thou jammed I will adjust for what I think is 15 that is the +/- 5 like wise for 20 thou off I normally set for 25. I have observed plenty of variance in the projectiles also the seating stems in the dies even the very expensive ones do not push or contact on what I believe is the Ogive so that make a difference and why your dies need adjustment for different bullets. It is not so much the seating depths once up and going that I am concerned about. I have it fixed in my head that is should be the same if only the comparison tool was exactly the same diameter as the barrel. I assume it is at the point that is meant to make contact with the lands on most guns. Where the Ogive is on a projectile is another point. They give different results depending on the projectile shape. It sits very deep over a projectile the others I use are Redding Seating stems that I use separate to any dies. Provides a relative measurement between the base of a case to a datum point on its shoulder angle.I have a couple of tools I use for the purpose one is a home made jobbie that I tried to replicate the bore of my rifles. This complete kit includes one Datum Dial tool for checking cartridge cases, Both bullet/Cartridge dials for use with 17 cal, 204, 224, 243, 257, 264, 277, 284, 308, and 338 bullets, laminated chart showing common datum diameters, instructions and storage box.
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