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I purchased a FN A1 SPR .308 cal.- I am getting anywhere from.0.178 to 0.98 groups depending on brand of powder and grns of powder. I am shooting the 168 grn Sierra MatchKings BTHP. I have found a load using IMR 43.5 grns tha I can get consistent groups average about 0.35 to 0.45 groups. I am wanting to tighten up a little more Si I have done some research on doing this and that to get to where I want. I am using fire formed cases to where I was full length sizing before, so now I am just neck sizing and trimming. I bought a Hornandy O.A.L. guage and a bullet comparator. I have always l reoaded from the manufacturer using the C.OA.L. which for a load from Sierra for the type bullet of the .308 is 2.80". In finding what my O.A.L. guage says on my FN rifle, I find it is 2.290". In using the reloading data 2.80" C.O.A.L. which is pretty standard looking at all the reloading data for the .308 cartridge I am measuring 2.206" to the ogive which puts me .084" off the lands, in which I was shocked to find that much freebore which is what I am getting my good groups from. In trying to tighten up some groups this is what I found. Now is the kicker I have tried extending my bullet out from O.A.L 2.210" - 2.280" and my groups go from 1" to 1.5" It seems to like it the best at .084 off the lands which is almost a 1/10th of an inch (not quite). I have not tried going the other way from .084 to .090
because it goe against everything I have read that .040 is about max you want to go from the lands. Has anyone one else discovered this in their rifle? This is a brand new rifle, if it was used I would have thought it has extensive throat erosion.
 
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