You are seating .020" off the lands, how does that compare OAL to the loading data you are comparing to? If you are seating significantly longer than the data you are trying to emulate, the pressure and velocity will be less. Have to add more powder to get the same velocity. Hope that makes sense.
I suppose this isn’t a thing I’ve really thought about. My plan was to start @ 20k off the lands with a bunch of different charge weights, find the most accurate one with along with some good velocity. Then I was gunna take that powder weight and mess with seating depths next. But you fellas are making me wonder if I’m thinking about that right.
No, you have that right. 0.020 off the lands is a great place to start. After you find a node or accuracy with your powder charge weight, then you can fine tune with seating depth if necessary. Some bullets are very finicky to seating depth and others aren’t. Just know that you may also see fluctuations with pressure and velocity, so monitor your pressure signs with any change……especially if you are playing with the upper end of safe loads.
I have never loaded 7 mag so I don’t have much to offer for powders based on your bullet weights. H1000 is a recommended powder and should do fine. Also….full length sizing is widely accepted by some of the best shooters in the world. Neck sizing, though still used, has mostly gone by the wayside. There are lots of great videos on YouTube that explain why….and Erik cortina has one of the best. You could learn a lot by watching some of his videos.
I do agree with all that above.
Neck sizing is only cause of the belt on the case.
If it didn't have a belt ,I'd say full length resize .
Remember it doesn't work well to neck size ,unless the brass has been fire formed to your chamber.
What happens is over time and many reloads,the brass will become very thin right above the belt ,if you full length all the time..
Hair line fracture will occur,right above the belt. You'll feel it with a finger nail.
At that point brass is trash.
I guess I would call it neck sizing,with a shoulder kiss.
When setting up a die to do this ,very important to make sure the case fits before reloading any farther,bolt should work as normal. Don't force it,just keep kissing the shoulder till she fits.
Ask me how I know ,get to the range and can't close bolt. No fun.