The not marking the paint at all is the part that I find baffling. I shoot at spinners with multiple .22 cal pellet guns, and even at ~15 FPE the paint is knocked off the steel. Something is either very wrong with the situation (are the pellets really even hitting the plate?), or that is some seriously good paint . . . .
Other .25 uses.Looking for a short range barn/shed rat rifle that would NOT blow through the galvanized metal siding or roof. Dents would be acceptable….holes not acceptable.Started testing….pretty quickly figured out it was the energy per square inch at impact that made the holes in a roof, not just the energy.14 foot pound .177 blows right though the non-rusted side of a rusted bottom galvanized tub (use as a substitute for the roof I didn’t want to fix).Area and energy. Both are 14 foot pounds. Force at contact with the sheet metal turns out to be 560 pounds per square inch for the .177 and 285 pounds per square inch for the .25.55a1c18a-8130-4ae5-a2b3-2e8069858e42 by Robert Dean, on FlickrThat slow .25 has turned out to be my best 25 yard rat-killer (distance from the patio to the infested shed).
Back to OP.What is your goal?The Royal is mainly a target gun, but you can tune it for rings or for hunting, not really for both in the same time/tune.As you said your friend tune it for BR so for precision shooting, that means less projectile speed. Imagine this... the speed is enemy for pellets.
Area and energy. Both are 14 foot pounds. Force at contact with the sheet metal turns out to be 560 pounds per square inch for the .177 and 285 pounds per square inch for the .25.
"A 68 pounder smoothbore and a 7 inch Armstrong gun firing 200 lb shot had been fired at 4.5 inch plate backed by 18 inches of teak. The 68 pounders had penetrated the target, while the 200 pounder had made hardly any impression on it. Noble showed that the answer lay in the relative velocity of the two projectiles. The 68 pounder had been moving at 1,425 feet per second when it struck, while the 200 pounder was loafing along at a mere 780 feet per second. On the face of it, the 200 pounder with 156,000 foot-pounds of energy should have out performed the 68 pounder with 96,900, but the low velocity of the heavier projectile allowed the plate to deform and resist the blow, whereas the higher velocity of the 68 lb shot tore through the plate before it could begin to absorb the blow.As Noble said in his paper, "What is wanted is velocity; if you sacrifice it to weight you will only be able to keep knocking at the door without entering."