Yellowhouse and Ranch, thank you VERY much for your suggestions. I have actually tried MOST of your suggestions. Never used Scheutzen or NOT crimped, but everything else.
At one time or another I have tried:Bullet hardness from pure to approx. 20-1, numerous hardness levels, ALL softer than my original Meisters
Goex 2F; 3F; Cartridge; Pyrodex; KIK
Sized @ .458", .459", & .460"
Different lubes including the yellow Bore Butter (but no SPG ... yet)
No paper-patch or chamber cast - I'll give that a try soon as I can get some CerroSafe, but I have slugged the barrel and got .4585", so .459" or .460 OUGHT to be OK, right?
ALL charges are dropped, then compressed about .125" to .1925" (with a compression die, NOT with the projectile)
Never tried the neck-tension trick ... yet. I DO size ONLY the "neck" & "orient" the loaded round the same each time.
I blow tube different times: #1 after every shot, #2 every 3rd shot, #3 blow every other shot then wipe @ 10, #4 wipe after EVERY shot, ...
I've never found Fed primers, but have used: CCI LRP, CCI Mag LRMP, Win LRP ... haven't tried any LPPs yet, Mag or normal ... yet
I didn't want to list EVERYTHING I've tried, but your VERY helpful hints prompted me to try.
As I see it, my WORST issue is that I have NO place to do a proper trial, I admit to having changed 2 or three details on the same bullet, so if something actually benefitted, I wouldn't know WHAT made a change for the better. To do it right would take CONSIDERABLE time and I simply don't have the time, place, money or other: I'm sorry to say that I'm looking for a "quick fix" ... but, as Yellowhammer stated (SO wisely), "Too many variables involved to nail down just one."
Thanks, Pards
and ... I haven't given up TOTALLY, just mostly, but I'm willing to slug anong before selling my 45-70 fencepost.
PS - I did forget to mention, I have only used Win cases, no others due to the ca$h required; also, I have changed the front sight from factory (a blade) to a Lyman tunnel, back to original. Also, my rear sight is a Lee Shaver Soule mid-range version. (Wish I'd have gotten the tallest one!)
And I STILL think it's the coolest rifle I own!!