Continuing to expand on the idea:
To simulate a battle a long range that closes to short distances (or starts at short distance and ends at long range).
1/ The event would require the use of a large bore rifle of any type - single shot or repeater using traditional BP loads for the cartridge, and a second weapon used at close range.
2/ The large bore must be used in or in excess of 50 yds to whatever distance the stage can accommodate.
3/ Close range would require the use of a second weapon, a shotgun, pocket pistol or full size pistol - shooters choice.
4/ Scoring would be a combination of elapsed time and required hits - any target standing when ammo is out is assumed to have killed you.
In example (scenario 1)
a/ Engage Buffalo sized target with 3 shots at 100 yards - shooter is allowed unlimited ammo but must hit three times before proceeding. Can shoot standing or sitting or kneeling with rest sticks - but not prone.
b/ Once buffalo is "killed" five Comanches are seen charging over the horizon thinking to catch a hunter out in the open.
c/ You can't hit an Indian charging at 100 yards on horseback but you can kill his horse - use rifle to shoot two horses (rifle targets) at 100 yards - but only one shot each - those you miss are still bearing down on you.
d/ If you knocked two horses down at 100 yards proceed to (e) - if you missed a horse or two at 100 yards you must try again at however many you missed (rifle target) at the 50 yard line - one shot per Indian missed only.
e/ They are now on top of you, if you have previously knocked two horses down use second weapon with five available rounds to engage three small targets at close range - these three must be killed before you proceed - if you need to proceed.
f/ If you failed to take down two horses at either the 100 or 50 yard line you now have to kill those you left at close range should you have any any remaining rounds - if not your dead - 10 minute penalty! Any Indians left alive inside 50 yards (close range) is assumed to have killed you.
G/ BONUS SHOT: Off the clock for those left alive. There are Indians shaking their coup sticks at you from 100 yards, saying things about your mother, you need to discourage this. Pick up your long range rifle and engage a rifle target at 100 yards. Kill the Indian with one shot and your time is reduced 10 seconds. Taught that rascal a lesson didn't you.
In example (scenario 2)
You are a scout in advance of a small vigilance committee hunting down desperadoes. Clearing a small hill on the southern plains you abruptly encounter your quarry - four renegades, three Mexicans, two proper looking fellows and a nasty looking Irishman going by the name of Books OToole. About 100 yards apart you stare at each other a moment until they open fire at you.
Step off of your horse and continuing to hold your reins in your hand you kneel to take a shot with your long range rifle at this group of bandits. You have as much rifle ammo as your belt or pocket will hold. The fight begins at long range.
a/ Engage the group (rifle) at 100 yards until you have killed 5 of your antagonists - when that is done they get really mad and charge you.
b/ Still holding your reins, engage them again at 50 yards with two shots at a rifle target - a hit is a kill.
c/ Drop your reins and seek cover behind a small rock and kneeling at close range (pistol targets) finish the remaining riders off with your second weapon, If you expend five rounds and any bad guys are left - you die - 10 minutes added to your score.
Or, something like that.