Some of you may have read of my ongoing affair with the .30 Sneezer, a .30-.357 wildcat that is suppressed and designed from the onset to shoot cast bullets. It has been a successful venture and an education. Part of the latter occurred this evening when I pulled out the concentricity gauge to evaluate some loaded ammo.
Given:
-Brooks Tru-bore custom mould that casts 183.5 grains of 30:1 alloy.
-Reamer by Dave Manson who also supplied the reamer sketch which was used to make the loading dies
-Dies by the Hornady Custom Shop overseen by Ben Syring
-Barrel by Bullberry
-Starline brass
The dies are a 3 die set of what I consider to be unusual design and I did not fully appreciate the nuance of this until my second discussion with Mr. Syring. The dims are excellent and somewhat subtle. The expander plug is tapered and leaves the neck at .3085 at the shoulder junction and .3095 at the case mouth. The only requests I'd made in the process was for a bullet that cast at .309 and neck tension in the .001 range. I got a better deal than that it turns out.
The seat die functions with a movable plug cut to spec for the bullet, and controls seating depth. I hesitate to call the crimping function a crimp as it is a taper of approximately .001" over the length of the neck (about .485" long). Bullet samples of where supplied to Hornady.
This evening I pulled out the C. gauge and found that bullets seated with the crimp were consistently less than .001 run out. Some other loads just assembled without the crimp but verified to chamber properly were less than .0005" on the run out.
I've dealt with significant run out in other bottle neck cases by the usual means successfully, but I would have never dreamed that the combination of a bottle neck case and cast bullets could be loaded with such absurdly low run out.
Kudos to those fellows, they synergized in a way that amazes me.
I am dazzled....
