Excellent point.. One which I was going to make until I read it first.
A wet chamber will not grab the cartridge and subsequently seal the chamber.
Consequently pressures will be inconsistent and accuracy will suffer.
The same holds true if your bullet is undersized or alloy too hard for BP to obturate the bullet base if at groove or smaller.
Paul Matthews wrote 4 small books on BPCR.
They are the best place to start before you load another round.
"Loading the Black Powder Rifle Cartridge"
"Cast Bullets for the Black Powder Cartridge Rifle"
"Shooting the Black Powder Cartridge Rifle"
"How -To's for the Black Powder Cartridge Rifle"
These books cover everything from lube formulas, bullet design / fit, blow tube techniques etc., etc, etc.
Great reading.
Because, as you know, there are so many variables it is difficult to know which
common denominators should be adhered to, to serve as a baseline.
And to make matters more complicated everyone has their own experiences which they believe
is the holy grail.
I have a friend who has a collection of actual antiques and or period correct rifles that could start a museum.
He does not have the time or inclination to do load development so he sends me a rifle now and then to work up a load. A practice I truly enjoy.
After determining things like twist and chamber dimensions from a chamber cast I have a good starting point.
I've ordered custom moulds from a few quality mould makers like Steve Brooks to match the specific rifle.
Even after doing this, sometimes without success mind you, I've turned to other moulds I have in inventory which I didn't think would work and to my surprise they turned out to be 1 MOA combinations.
I mention this because there is no reason to be discouraged. One Mould may work in one 45-70 and not another. It's best to mess with only one variable at a time, otherwise you will never know what it working and what doesn't help improve accuracy.
BTW, I have and enjoy a Uberti Hi Wall in 45-70.
The first thing I did to it 20 plus years ago was to change the butt stock. For me that crescent shape was a punisher. It now has a shotgun style stock with a recoil friendly pad.
Consistency is probably more important in BPCR reloading and shooting than in high velocity shooting disciplines, although benchrest, long range guys will beg to differ.
The following is the MOST Important part of the sport;
Have fun, keep good notes, have more fun...
Bob