My experience with Trail Boss
Several years ago when I was teaching a friend how to reload, I suggested Trail Boss to learn with because it fills a lot of volume for the power it delivers. Hard to miss an undercharge or overcharge because the powder is easy to see inside the case.
But this was during a shortage of components and my friend had bought jacketed bullets (actually for the 500 AE) for use in his 500 S&W revolver and there were no .500" lead bullets to be found anywhere in town.
I could not find data for jacketed bullets, though, so emailed Hodgdon. Their answer was that "Trail Boss does not like jacketed bullets."
I emailed back, "How does Trail Boss express this dislike for jacketed bullets?"
I never got an answer to my second email.
The emails were longer than the quotes, but the quotes are verbatim.
I dug around Hodgdon's web site and found that Trail Boss is a smokeless powder developed to be used as a substitute for black powder in the Cowboy Action Shooting Sports fairly recently and was very new at the time.
I have observed that TB is now being used and even recommended for plated and jacketed bullets elsewhere but Hodgdon still lists no loads for jacketed or plated bullets on their web site:
http://www.imrpowder.com/data/rifle/trailboss-oct2005.php.
What has NOT changed about TB is the ironclad recommendation against compressing a charge I find in all discussions about TB. Apparently the flakes behave badly if they are either 1) broken or 2) without a little air space between them. I don't know which.
Hodgdon's web site suggests, "Call 913-362-9455 for more information."
My friend and I loaded his jacketed bullets with TB and got 700 fps with 350 grain bullets out of his 500S&W. They are a hoot to shoot. Recoil is like a 22 rimfire in that heavy gun and if you are fast in the right light, you can sometimes see the bullets travelling downrange. We don't load that slow any more. He (safety first!) keeps the velocity above 850 fps and uses lead for TB loads now that we have a source for bullets.
I don't know if our experiences help. I hope they do.
At what range are you measuring the point of impact? Can you tell us a bullet velocity?
Lost Sheep