John, Thanks so much for your reply. So, does your rifle produced a lot less velocity for the specified powder charge than Nosler shows in their latest guide, #8? Mine sure does. Nosler got 3046 fps with the 160 grain and 61.5 RE-19. (Nosler case, Fed 215). Mine gives 2893 fps with the same load (WW Case, Fed 215). Nosler got 3058 fps with the 160 grain and 63 RE-22 - mine got 3003 with the same (much closer to their spec) I tend to think your idea of powder lot variations may be the main reason for the differences I've seen between your Handloader #327 loads and the two of them I've tried. Since I got much higher velocity than you with two different bullet/powders (160 AB/IMR 8133 and 175 ABLR/Magnum), when my "paradigm" is getting less than published, I figured maybe there were other factors involved. At least three things I would guess should be expected to get me LESS velocity than you, if everything else was equal. These are "noise level" differences but all finite and cumulative. 1) your barrel is 0.4" longer than mine. 2) you're measuring at the muzzle with your Lab Radar. I'm measuring 5 yards downrange with a 35P. 3) I am seated the same distance off the lands as you were (.025") but that results in my ammo being .010" longer than yours, which makes me think I have a throat that much longer and thus equal "jump" between our loads would indicate a little more case volume in mine.
We're using the same primers, Fed 215, but my brass is older but once fired Winchester (W-W Super headstamp). I prepped 50 rounds and found them very consistent. they averaged 229.5 +/- 1.0 grains. If your Hornady brass was a lot lighter than that, there could be another of the factors. Do you have the weight of those cases?
Despite being almost 30 years old, I've actually shot this 7 Mag very little. I killed a couple mule deer with it soon after getting it, but then got a bad case of Rifle Loonyism and started acquiring other rifles, and the 7Mag sat semi-retired until this year. Its throat is in great shape - no erosion there.
And your final statement above makes me want to get a confirmation from you: "All of which is why I advise loading to velocity, not the powder charge." RE: Nosler's top load with the 160 AB and 61.5 gr/RE-19 at 3046 fps. I am up to 63 gr/RE-19 and still only getting 2979 fps. I reckon you'd say keep going to that velocity? If I was getting the accuracy I wanted at 2979 I'd be happy, but would like to see what it does closer to the same pressure Nosler used, since their fastest load with RE-19 was the most accurate.
