Its like Daryl said.
Sniper68, congratulations, very few people think to do something like this.
Wondering just what variations in weight meant I once glued down a row of 380 gr 40 caliber BPCR bullets of different weights from the same batch of bullets and machined down through them .010" a a time.
I found no actual voids such as Sniper did. BUT I did find a difference in metal density along the centerline. In the bullets within 1 grain of nominal this was very uniform and as I machined down though this area of reduced density appeared and then disappeared uniformly. I.E. it got bigger as I cut down through the bullet to the centerline, then it got smaller as I cut deeper and then disappeared it matched the contour of the interior of the bullet pretty well but was fairly small, probably .05 wide at its widest point. It was well centered.
In bullets more than a grain light I found that the area of different density was NOT uniform. It would increase and decrease in size as I machined through the bullet and was off center at some points as well.
Lighter bullets tend to have air holes in them. Nice round bubbles at the base.
These bullets were all cast of an alloy made from lead and linotype (the bullet design required a hard bullet for accuracy), not pure lead. A ladle was used, this has proven to make the most uniform bullets for myself and other people who have cast a LOT of bullets over the years.
It is impossible to load match grade cast bullet ammunition if the bullets vary more than 1 gr +- and if things are going well it is possible to cull to +-.5 gr.
The bullets I check that were 2-3 grains OVER nominal, there are always a few, were SOLID no variation in the metal.
I believe that these differences in density and Sniper68s holes in RBs are the result of cooling and shrinking of the metal.
I weigh all cast bullets or balls for the above reasons using a digital scale, anything more than 1 grain "out" gets recast.
Slower twist rifle barrels, 48 or 72" etc are less effected by anomalies that a 16-18" twist slug or cartridge rifle. But it has to make a difference. But it may not be very apparent in limited testing. 1 or 2 10 round groups may very well be inconclusive just due to variations in the shooters performance at any given time.
I have no doubt that the cast ball is more accurate than the swaged ones, since none of these I ever checked were actually round. The cast ball generally is pretty round. I have no doubt that the weighed ball will out shoot the general run bullets, though a good mould and careful casting will produce a very uniform bullet/ball once the temperatures are all up and a uniform routine established. But there will still be variations and variables are what must be eliminated if shooting is to be its best.
Dan
