excessive bullet runout on new 7-08 AI
I could use some advice on a problem with a new chambering. A friend just gave me a new stainless take-off barrel in 7-08 from a 700 CDL, and I had a gunsmith rechamber it to 7-08 AI and I put it on a proven 700 short action that Iíve had for about 30 years.. I had some new Lapua brass in 308 and using some new Hornady dies I necked down the necks so that it was a firm fit in the new chamber and fireformed the box of loads by taking it along on a sage rat hunt.
I bought a new Redding FL die in 7-08 Imp. and loaded enough rounds for several groups using both Nosler BTís and Hornady SSTís, both of which I had on hand. I used the Hornady seater, which is a ďDumoreĒ die which should work for everything from 7-08 to the 7mm belted mags, maybe even bigger. The groups ranged from 1.25 to about 2Ē, which is pretty disgusting. On my return I ran the remaining loads thru a runout indicator and there was as much as .012 runout on the bullets. The runout on the necks of the fired cases was almost nothing. I had not turned down the necks of the brass yet, but obviously checked to be sure that there was clearance for the loaded necks.
Any ideas about whatís causing this runout? I did not think to check the runout on the virgin brass that I loaded for fireforming, and itís too late now. Iím thinking it might be the seating die. Most of my life Iíve used RCBS dies and have not had a problem other than many of the sizing dies being tight, which I correct with a drill press and valve grinding compound. Have any of you used the Hornady dies with the universal (for caliber) seaters? Another possibility, it seems to me, is that the expander nipple might be pulling the necks off-center.
Iím a deer hunter, not a benchrest shooter, and if this rifle will shoot ĺĒ groups Iíll be happy, and if it shoots ĹĒ groups Iíll be delighted. Since this runout is much more than any of my other rifles I think I should look there first before condemning the barrel.
Thanks for any input.