While I'm by no means new to reloading, this one has got me scratching my head big time. I purchased a Weatherby Vanguard Range Certified (guarantee less than 1 moa) new not too long ago along with 100 new Lapua brass cases. Originally stated load development with IMR 4895 and then the powder shortage set in and I had to switch to IMR-4064 as I was able to get 14lbs of it. Throughout load development I only neck sized. Best load seems to be 49.0grs IMR-4064 with bullet seated .011 off the lands with groups 50% of the time under 1/2 inch and some 1/4 inch and the other 50% around 3/4 inch to just under. In an attempt to get more consistent groups I had already eliminated everything I could think of....EXCEPT headspace as I was only neck sizing, nonetheless I figured let me just check headspace...and man was I in for a surprise.
Of the 100 lapua cases fired out of the Weatherby the cases measure anywhere from .003 to .017 BELOW max headspace for 30-06 using Wilson case gauge along with Wilson case gauge depth micrometer. So I took 8 cases that all had the same headspace and loaded them up and shot them today. Four shot 3/4 inch group and four shot 3/8 inch group @100yds and once again noticed several primers were slightly above flush (having seated them .002 below flush with tight primer pockets. A buddy of mine at the range said you might have too much headspace so measure the case with the primers in them and then measure w/o the primer. The result are as follows: with primer .002 - .004 below max. w/o primers .004 - .012 below max. so at this point I pulled out my Hornady Headspace Gauge and cases measure 2.035 - 2.040 now If I'm reading SAMMI spec correctly max headspace is 2.052 -.007 setting minimum at 2.045. So best case I'm .005 shorter than minimum and worst case .007 shorter. How in the heck is this happening, I thought cases were supposed to stretch to eventually fit the chamber....remember I haven't FL sized any. I'm lost and would appreciate any insights. Thanks.
Of the 100 lapua cases fired out of the Weatherby the cases measure anywhere from .003 to .017 BELOW max headspace for 30-06 using Wilson case gauge along with Wilson case gauge depth micrometer. So I took 8 cases that all had the same headspace and loaded them up and shot them today. Four shot 3/4 inch group and four shot 3/8 inch group @100yds and once again noticed several primers were slightly above flush (having seated them .002 below flush with tight primer pockets. A buddy of mine at the range said you might have too much headspace so measure the case with the primers in them and then measure w/o the primer. The result are as follows: with primer .002 - .004 below max. w/o primers .004 - .012 below max. so at this point I pulled out my Hornady Headspace Gauge and cases measure 2.035 - 2.040 now If I'm reading SAMMI spec correctly max headspace is 2.052 -.007 setting minimum at 2.045. So best case I'm .005 shorter than minimum and worst case .007 shorter. How in the heck is this happening, I thought cases were supposed to stretch to eventually fit the chamber....remember I haven't FL sized any. I'm lost and would appreciate any insights. Thanks.