What type of firearm is lawful during the Muzzleloading season? (taken from Massachusetts DNR regulation page)
A shoulder-fired muzzleloader .44 to .775 caliber. Barrel length must be 18 or more inches with only onebarrel operative. In-line ignition systems are permitted providing the rifle loads from the muzzle and doesnot have a break-open or hinge action (like a single-barrel shotgun). Buckshot is prohibited. Only single projectileammunition is permitted. Sabot rounds are legal. Powder is limited to black powder or approved substitutes. Scopes and 209 primers are legal.
Looking over your regulations for Massachusetts, I am wondering if a break open action like found on the Omega, Sidekick, Encore, Pro Hunter, and many other rifles is actually legal. How do the rest of you interpret this law? While there is not a lot of detail as to what the actual hinge action implies, whether loading a 209 primers, etc. I think reading this, they might be illegal. For that reason I would suggest you purchase a Knight Long Range Hunter in .50 caliber or a Knight Disc Elite. These are still the bolt type but the breech is technically sealed and water will not be a factor for you. Also they are considered one of the best long range sabot shooting rifles on the market.
If you want to throw large conicals at the critters with extreme accuracy, then look for a White Super 91-II in .451 caliber or .504 caliber. Both will shoot extremely well and get the job done. While White is not technically in business there are a lot of rifles out there to be found if you know where to look. White's shoot large lead conicals (and sabots extremely well also) with great accuracy even at long distances and with a lot of down range energy.
Outfit any of these rifles with a quality scope and I think you have yourself at least (with practice) a 200 yard rifle able to take down about anything you want to hunt.