Hate to disagree with some of this, BUT a bullet seated 0.06" deep to COAL will NOT increase pressure in a 45-70. It will likely decrease pressure. These chambers are not high precision target chambers machined to incredibly tight tolerance. COAL is there so that the 45-70 ammunition will feed from a tubular magazine in a lever action. That is pretty much it. The chamber is 'generous', loose and large, in most any commercial lever rifle. That's right! So it will feed in those big slightly tapered rounds what are covered with pocket fuzz, been dropped in the dirt two or three times already when unloading the rifle, covered in sweat and grease as they are rolled around in your hunting jacket pocket as you play with them while waiting for that elusive elk or big buck.
Don't know where I saw it but there are some great charts of pressure readings done where seating depth was varied within some pretty extreme limits from 0.1" 'deep' (yes, that is correct) to jammed into the lands, by 0.01" increments. The ammunition itself was loaded with identical amounts of powder close to a maximum charge with the same case, bullets, primers, and neck tension. The only pressure increase noted was as the bullet approached the lands and then spiking significantly when jammed.
Another similar test I did personally, showed that the velocity only very slightly increased during my seating depth testing on my custom 6.5CM, my factory 5r .308, and my smith rebarreled SAAMI minimum chamber and 'accurized' REM700 5r .223. as I went from .030" to 0.005" at 0.005" increments off the lands with each rifle. As well, Hornady tenth edition reloading manual states this same information on pages 23 and 24.
This doesn't mean you can't take things to ridiculous extremes to prove a point, but as a general rule of thumb, pressure decreases with increased seating depth, and pressure increases as the seating depth is reduced and the bullet gets closer to the lands.
AND, with a 45-70 lever gun, I can absolutely guarantee that the last thing on the manufacturers mind was benchrest accuracy!