Yes, it would be right at home atop a muzzleloader.
Mark H.
While Aimpoint recommends the
https://www.opticsplanet.com/aimpoint-30mm-rings-wide-stainless-camo-or-black.html
the one review is not positive.
I would recommend a medium height ring, such as the made-in-the-USA Warne 513M:
https://www.opticsplanet.com/warne-30mm-fixed-pa-riflescope-rings.html?_iv_code=UY-RR-30FPRR-514M
Mark H.
Yes, Henry makes weaver mounts that will allow you to mount this with rings, however which rail you need depends on which generation, first or second, your Henry Big Boy is. Please contact us at techsales@opticsplanet.com with that information and we will be happy to assist you further.
This does not come with any mounts, but it fits any standard 30mm rings or mounts. To co-witness with the backup sights on your AR-15, you would just need a 30mm AR mount such as these: https://www.opticsplanet.com/vortex-30mm-cantilever-riflescope-ring-mount-for-ar-15.html