When you start fighting Magruder, draw him towards the thermal vents(which are on the floor) and, when he is within a few seconds of arriving, you can shoot an arrow from the Loco Dynamite Bow at the vent, and when it explodes, a stream of fire will shoot up, and hopefully hit Magruder After he is almost dead, he will get up on a stage, or something similar, and throw dynamite. As soon as he throws it, enter quickdraw and shoot the dynamite. You only have a few seconds, so shoot it quick. If done correctly, he will say 'you're blowin' the place apart!' -to get him angry, get a headshot in on him
Unlock Apache Shirt: Complete ALL Hunting Missions
Silver Spurs: Complete ALL Pony Express Missions
Unlock Reed's Armored Horse and Macgruder's Cannon Shotgun: Complete 'Story' mode and ALL side missions getting 100%. When completed Reed's Armoured Horse is at Macgruder mine and the gun is given to you.