Handloader did a couple of years ago.
What they found out was, the 70% starting load was so slow in most rifle calibers that the bullets would not stabilize and even sometimes key-holed.
They said the best accuracy in about every caliber they tested was loaded to the base of the seated bullet.
They did not say to skip the starting load work up in so many words.
But they might as well have said it.
rc
I believe it. I bet they also found a 70% fill was erratic. A full case full is still pretty slow. Works great, but is nothing more than a light plinking load unless it is a really big case and a heavy bullet. A case full (100% load density. Powder loaded to bottom of bullet.) under a 350 jacketed bullet in .458 Win Mag gives me just short of 1200 FPS, which is around .44 Mag power, but just a little poot in a near 9 Lb rifle. ES & SD numbers are not particularly good.
I am beginning to think you can't hurt yourself with Trail Boss at 100% load density without compressing the powder more than 1%. (That is NOT a suggestion to start going around filling cases full of it while ignoring data)
I loaded two .357 cases with Trail Boss at 101% load density (Well over the data!), under an X-Treme 158 Gr SWC using a WSP primer. I shot them yesterday at 65 degrees. One one went poot, and gave 517 FPS, the other gave a little bigger poot, and gave 681 FPS.
My advise with Trail Boss and pistol calibers is to stick to lead bullets. I keep trying it with plated, and it keeps telling me to stop.
Rifle calibers? Use 100% load density with no more than 1% compression..
As always, use proven data in load books and PDF's put out by the powder companies. Any experimentation on your part could lead to damage to you or your firearms, or worse.