Deeper seating will in many guns, increase pressures, sometimes considerably if the original longer seating still cleared the rifling to start with. There are so many vaiables in handloading, one must work up his own loads.

Straight cases are the most difficult to work with, as they don't have a shoulder, which helps hold back the powder to get goo dignition started. At the bullet moves forward, just a small amount, the expansion ratio is hugely effected, dropping pressures and the 'flame'.

Thus, being able to use a compressed or at least a full case of easily ignited powder (or stronger primers) is the best scenario for straight cases. Years ago, John Buhmiller has such problems himself with straight cases and wrote about it. He resorted to testing with double primers - one in the pocket and another on top of the powder undeneath the bullet. I did similar testing in a strong bolt action rifle. I am not suggesting anyone try this, as I mention it only for others to gain an understanding that there is a real problem with ignition in straight cases and means must be found by each and every loader to circumvent the difficulties.

Again, I would not do this in a double of vintage and would not suggest anyone try it - period.