I didn't have my BC chart handy- so assigned a BC of .080 which is high but close for a .54, I chose 225gr. for ball weight and a .54 cal. as Crow Killer didn't say what it was. Due to the higher BC of the .54's ball, it will be flatter shooting at any mormal hunting velocity than a .50. This will give the most credence to what Crow Killer is claiming for his rifle.
Crow killer noted his rifle "seems to be sighted or zero'd at 150 yards"(who adjusted the sight?). Seems is a strange way of putting it as we choose to sight our rifles at a definite range - our choice - not what someone else has done. If wrong, we re-sight the rifle. Really doesn't matter here. What does matter, is the midrange trajectory noted - glad it has been acknowledged that there is a midrange. Zero'd at 150yards but only a 3" midrange seemed a mite flat shooting to me.
I assigned a velocity of 1,900fps - somewhat higher than 100gr. powder will give. We don't know Crow Killer's load nor the velocity he is getting. I assume he has no chronograph.
At 1,900fps and zero'd at 150 yards, that 225gr. ball with a BC of .080 will be 5.1" high at 90 yards, the highest travel in it's arc to the target.
At 1,900fps and zero'd at 140 yards, that ball with a BC of .080 will be 4.1" high at 80 & 90 yards, and will 1.7" low at 150 yards. It would be difficult to see in a low-shot group if the rifle was zero'd at 150 yards or closer to 140 yards.
In order to hold the midrange to 3" as Crow Killer noted, the rifle would have to be zero'd at 127 yards. This would give a 70 and 80 yard impact 3" high, and at 150yards, the ball would be 3.7" low, not zero'd - that is impossible to achieve with a round ball with normal, heavy hunting loads.
If we raise the velcity to 2,000fps, which would probably take something like 120gr. of powder, we see perhaps the best possible trajectory. Sight for 131yards, and the ball would have a 6" kill zone to 150yards. That means the highest midrange is 3" high at 80yards, zero'd at 131yards and 2.9" low at 150yards. Given one hole accuracy at every range, all the balls would strike within 6" to 150yards. Of course, I hope we all realize this just isn't possible either. No rifle will put every ball (or bullet) into the same hole - at any range, when hand-held - even rested.
Thus we see it is impossible to have this rifle zero'd at 150yards and give only a 3" midrange trajectory. It is impossible, whether it be a .50, .54 or .58 - smaller than .50 or larger than .58 - does not compute - won't happen.
When a person says his rifle shoots -------- 'about' or 'seems to' or 'approximately' - he is talking about perceptions, not actual fact.