Apologies for the delay, our dilemma was due to the card text:
Shootout: During this round’s resolution, both players gain +1 hand rank for each Horse in their posse. One dude in your posse becomes a stud until the end of the shootout.
There is no phase called 'resolution.' This is the current ruling regarding Calling the Cavalry:
Calling the Cavalry is resolved as a standing effect during the Reveal and Resolve phase. The bonus hand ranks start when Reveal and Resolve does and constantly check the # of horses. So, if I start Reveal and Resolve with 5 horses, my Hand Rank is +5. If you use an effect (lets say point blank gets a dude with my horse) I go down to +4. I move a dude in (like Warren Graves with a horse, and the new guy Vallejo in TCaR, in response to Point Blank or another card) I then am back to +5 hr.