Question "best gauge for rabbits and grouse."
Question "Also what length of barrel would you go with for a decent pattern."
I will answer this string with "modern cartridge shotgun" experience and then transition to black powder.
Rabbits and grouse are very different game. When hunting them with my modern cartridge shotguns, I prefer a 20ga, but have also used 12 ga shotguns with shorter barrels and an open choke. Both rabbits and grouse are easy to kill, you don't need a lot of pellets to connect to make an ethical kill. I prefer 7 1/2 to 8 shot for grouse and 6 for rabbits.
Using my modern experiences, I then would make the following muzzleloading recommendations.
- Shot, I would use 7 1/2 for grouse and 6 for rabbits. High quality chilled shot.
- Both game, rabbits and grouse, are quick to flush. A well tuned lock, that sparks good and provides for a quick ignition is a must. A slow flintlock ignition will result in many a missed harvests as your shot will arrive after the quarry has passed your point of aim. You may get a shot at a stationary rabbit, but this never happens with grouse.
- A shorter barrel length translates into a quicker swinging firearm, which is a plus in hunting upland game, especially grouse.
Now taking the above facts. Do you want to only use a muzzleloader as a shotgun or do you want to also shoot roundball for deer?
Gauge recommendations:
- All purpose deer, grouse, rabbit I would prefer a .58 cal / 28 ga. Primary reason availability to factory roundballs. So I can practice practice practice.
- If I only want to use it for rabbits and grouse, a .62 cal / 20 ga. Unless I cast my own round balls. 20 ga wins out in my mind large shot load.
BUT THE KEY HERE IS PRACTICE - PRACTICE - PRACTICE, muzzleloaders on the fly is not as easy as you thing. Shoot lots of trap to learn the mechanics of muzzleloading shotguns.
