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Posted: 11/6/2010 4:11:00 PM EDT
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I seem to have excessive runout and I can’t figure out where I’m going wrong.
I start with new Lapua 308 brass, neck measures .015”, expand neck with Sinclair Gen II expander die, full length size with Redding S .336 bushing expander ball removed, trim to length with Wilson trimmer, chamfer/deburr, and check with Sinclair concentricity gauge. Cases are between .001 and .003 runout. I then prime, powder, seat 175 SMK with Redding competition seating die, and check runout again. My runout is now all over the place anywhere from .002 to .011 for finished product. I try to measure the runout near the ogive. I am just trying to get .003 or less runout and can’t seem to get there. I am using a RCBS rock chucker press. I am sure that I’m doing something wrong but I can’t figure out what I’m doing wrong. |
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I use the exact same tools as you except the press(Hornady Classic single stage for me) and I'm loading .223 Rem & 6.8SPC, but as far as run-out goes I'm a little puzzled by the increase after seating the bullet as I don't usually see any increase after seating and sometimes a slight decrease is the norm. Really you shouldn't worry about the first loading so much as the brass will get straighter after the first firing(assuming you have a straight chamber) and when you reload it you will then be able to see the real potential of the brass and dies. I usually load a light load for the first firing just to fire form the brass to my chamber before worrying about how good the run out is, after reloading I end up with sub-.002" of run out with the majority being under .001"(some the run-out gauge needle doesnt even move).
Shoot it and check again after reloading and see how it is. |
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Do you have the die adjusted properly? The die needs to encapsulate the neck to fully support it while seating the bullet. Re-read the dies instructions to insure you have it installed properly.
I use an expander mandrel to establish finished interior neck dimensions. By just resizing the neck exterior you push all of the imperfection to the interior of the neck. While Lapua brass is a good as it gets, nothing is perfect. By using an expander mandrel (Sinclair International, K&M, ect.) you establish a perfectly centered neck of uniform dimensions. Any exterior imperfections can be turned off or sorted and seperated. Some brass just will not make it. It needs to be seperated and used for fouling shots, hunting or offhand practice. Pick the best of the breed for serious accuracy work. |
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Quoted:
Try rotating the cartridge 90 degrees while seating. Seat the bullet about half depth, rotate, then finish seating. It's possible there's a problem with your die. This! No matter how straight your brass is, the seating die is not a perfect fit on all bullets/ogives, so will give runout. If you check the ogives and OAL on the bullets, very few are exactly the same I seat mine turning 120 degs while seating and get .0015 and under. 'Borg |
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