milkman
02-03-2014, 04:12 PM
I received a Hornady Concentricity Tool for Christmas and thought you might be interested in my experience with it so far.
The tool is designed to measure and correct bullet run out. If your bullet is lop sided in the brass, this tool is supposed to show it and correct the problem. The tool has 2 non- rotating centers with movable dial micrometer in between. The loaded round is placed in the tool and rotated by hand to find how much run out there is, then an adjustment screw is run in, from the opposite side of the micrometer, against the neck at the low point of the run out and the screw forces the brass back into line.
The tool does work as advertized. All my dies are Lee, and as I had read, Lee dies seem to have less run out than most others. Most of my loaded rounds were at about .oo2" to .oo4" run out. The instructions say that anything less than .004" is not detectable on the target, however, I was able to adjust most to less than .002".
Most cases with larger amounts of run out showed to be out of true at the bullet, neck and below the shoulder. In all cases, with these, when the bullet run out was corrected as much as possible, the entire cartridge measured better than before.
There are some problems with using the tool with cast boolits. The nose centers do not have large enough holes to accept flat nosed projectiles over 30 cal. Even 30 cal was a poor fit on the largest of the centers. A good friend with access to a lathe made me 4 custom fitted for my caliber boolits. Also soft projectiles deform with the pressure of the adjustment screw and either the nose bends or they allow the neck where the screw presses to dent. Boolits of water dropped 50/50 seemed to work ok.
Does the tool help accuracy? I dunno but it has been fun playing with it.
The tool is designed to measure and correct bullet run out. If your bullet is lop sided in the brass, this tool is supposed to show it and correct the problem. The tool has 2 non- rotating centers with movable dial micrometer in between. The loaded round is placed in the tool and rotated by hand to find how much run out there is, then an adjustment screw is run in, from the opposite side of the micrometer, against the neck at the low point of the run out and the screw forces the brass back into line.
The tool does work as advertized. All my dies are Lee, and as I had read, Lee dies seem to have less run out than most others. Most of my loaded rounds were at about .oo2" to .oo4" run out. The instructions say that anything less than .004" is not detectable on the target, however, I was able to adjust most to less than .002".
Most cases with larger amounts of run out showed to be out of true at the bullet, neck and below the shoulder. In all cases, with these, when the bullet run out was corrected as much as possible, the entire cartridge measured better than before.
There are some problems with using the tool with cast boolits. The nose centers do not have large enough holes to accept flat nosed projectiles over 30 cal. Even 30 cal was a poor fit on the largest of the centers. A good friend with access to a lathe made me 4 custom fitted for my caliber boolits. Also soft projectiles deform with the pressure of the adjustment screw and either the nose bends or they allow the neck where the screw presses to dent. Boolits of water dropped 50/50 seemed to work ok.
Does the tool help accuracy? I dunno but it has been fun playing with it.