Our Club 200 yard offhand gong matches I use a 290 gr Spritzer bullet from a LBT custom mold in my  38/55 CPA. Guy that beats me all the time uses 250 gr store bought 38/55 bullets in his Browning High Wall

We shoot and practice together a lot. I can see no negative with his 250's.  Shooting the same rifles at 500 meters on our Buffalo gong his 250 gr outfit has not shot as well as as the 290's in the CPA. I suspect the difference is very slight as distance increases and more accountable to all the possible variables than the bullet itself.

As far as flat or round or spritzer. My experience is at BP velocity modest range it makes very little difference. That 38/55 CPA have molds for all three and can't see any difference in performance at 200. Only shoot the LBT Spritzer at longer distances so have no frame of refrence for the flat or round nose.

Boats