My method is a little simpler and cruder, but it works for me -I take a sized case and load a dummy long, then try to load it in the chamber. Bolt won't close? Don't try to force it, use a coated cleaning rod or a wooden dowell to gently tap the dummy out of the rifling (it's probably stuck there). Remove cartridge, adjust seating die to seat 5-10 thousandths deeper, repeat.

Eventually you will be able to close the bolt with some effort. Extract dummy, adjust seating die to reduce COAL in about 3-5 thousandths, should chamber easily now. Make a second dummy with a new bullet/case, leave seating die at previous setting. If you've done it correctly you can NOT feel the bullet engage the rifling (bolt closes easily), when you extract the case you will see the light "witness marks" from the rifling on the bullet - this is a light kiss and the place to start load development.

I like to make at least 3 dummies to check magazine function for any load I develop, so this is just part of the process. If you later realize that a slightly shorter COAL shoots better, its no big deal to run your dummies back through your seater to adjust to the new length.

Picture shows witness marks from the rifling on the bullets - look at the area where the pencil is pointing. Note these rounds have been run through the magazine many times for function checks, so there are a bunch of rifling marks - would only be ~4 or 5 after the first check with a previously unchambered dummy.

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Now go back and check COAL on the dummies you just made - don't be surprised if COAL varies by 3-5 thousandths between dummies. The bullet length can (and will) vary. The seater seets based on the ogive, not on length and as such seating depth will be consistent w/ regards to ogive/rifling regardless of variations in bullet and/or COAL.

HTH

David