Good job! I am looking forward to hearing of your results. I have been shooting my M28/76 action for a couple of months now. Let me share a couple of osbervations, maybe you can confirm or deny what I am finding.
1.) SLUG the D-166. That is a chamber spec, not a bore spec. My D-166 slugged @ .3082 Groove diameter. The bore diameter looks to be @.300, but grooves are harder to measure on the slug.
2.) .308 bullets do not touch the lands in my D-166 barrel at OAL.
They DO in my M28-30. Both are supposed to have a .3082 groove, but the bores do not start the same.
3.) The D166 Lapua 200gr WILL hit at OAL, because it is the fatter bullet. The Berger VLD's (215/190gr) are @ 3.25 before I get meat on the bullet, then there is very little to crimp.
Sierra's work well even when seated off the lands, still the most solid bullet choice for overall use. 200gr if you can get them!
Just thought I would let you know before you spent a lot on exotic .308 bullets. Do not waste your time with the TSX bullets, they keyhole unless they are seated perfectly. Out of 25 or so that I shot, only 1 group of 5 seated in between the 2 top cannelure's would not.
I have read threads on other calibers doing the same thing.
Let me know how it goes!
Oh, here is the tool Shep showed me how to make (empty cartridge) to test the seating:
Place the bullet in slightly and chamber, then withdraw carefully and measure.
The neck is cut in 4 places 90 degrees apart, perhaps not as deep as I did, so that the bullet can be easily removed. You may need to lube the bullet ogive a bit so it does not stick in the bore.
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