45 cal Colrain .435 rb .015 patch mink oil lube. starts with thumb pressure and loads easily with the ram rod. Below 70gr. 3f accuracy is poor. over 80gr 3f and the patches burn through. When loading a loose patch/ball combo you need enough powder to get the ball to obturate and seal the bore. easy to do in smaller calibers. haven't had any luck in my 58 so I coned it. .565 rb .030 patch loads and shoots great.
We've had the obturation argument using round balls here a few times, and in other forums and I've thought/considered the same as you about loads. At some point, there is or must be an obturation pressure, even for round balls - but- will that happen before gas blow-by ruins the patch completely? The higher the pressure/velocity, the more chance for burning and blow-by: - thus, there must be or probably is a fine line for a given patch, that may be approached quite closely, but not passed. If, per chance the ball obturates before the patch is destroyed, fine.
In using .562" balls in my tight (574") model 1861 rifle with it's progressive depth rifling, the patch does not reach the bottom of the grooves when the patched ball is on the powder. This is because when driving it into the muzzle, the ball and it's .0225" to .0235" patch are compressed from their original size of .607" to a maximum of .580" in diameter(.003" depth rifling per side, at the muzzle). At the breech, the rifling is .008" deeper per side, so the groove depth is .596". With a charge of 85gr. 2f and a velocity of 1,308fps, the patches are actually re-usable, showing the soft lead ball (somewhat elongated ball) must be slugging up to fill the grooves at the breech, even with this load. Now, Forsyth noted back in 1860, that the ball or bullet would slug to fit the bore BEFORE it started moving. Writers since that time have said the same thing - but - I suggest there is another criteria for this to work, thus this will depend on the quickness of the pressure build curve, compared to the mass and 'purchase the projectile has on the bore, ie: the resistance the ball has to forward movement allowing or not, the obturation of the ball or bullet.
I prefer to use tight loads, snug, as Wade says, that give good accuracy right from the get go. No matter what load is used, they still seal - producing quite literally, reusable patches - if you wish. Yes - the edges fray a little from muzzle blast, and fray even more the higher the pressure. More powder, more pressure. In my loading, the sealing part of the patch, that part that touches the bottom of the grooves, is the barrier between the ball to that pressure and flame. It MUST maintain it's integrity and continue to seal ALL of the powder gasses behind it.
