I definitely agree that - now that we have better ammo for our cannons - we need some infantry armament, ideally rifled. Right now, we have a breach-loaded rifled bess variant (Fast Action Rifle Mk. I) and a percussion-based one (Imperial Rifle Mk. I).
My concern with both is that they are fairly ambitious designs, and we risk failure either due to explosive breach-complication or failure of the percussion caps.
Therefore, here's my alternative design:
The Long-Range Rifle is, in essence, what will be known as the Baker Rifle. It consists of a 760mm, 16mm-calibre rifled barrel in which seven grooves are cut. Contrary to the Baker Rifle, and expanding on ammo observed to be used in the Samara rifle, it uses a cast soft-lead bullet which will expand on being fired, grip the grooves and clean them of blackpowder residue. This takes away with the necessity of wrapping the ammo in cloth, therefore increasing the reload speed to that of a contemporary musket. Powder is issued - as usual - in paper cartridges to be ripped open and poured into the rifle; riflemen are additionally issued a powder horn for more accurate shots.
In the end, the rifle will be able to accurately hit a man-sized target with 90% of its shots at 300m, and marksmen will be to fire accurately up to 500m.
The idea is to primarily issue these rifles to skirmishers (once we have enough, everyone gets one), but I expect them to be expensive. These skirmishers primarily fire on Victoria-carriers and officers during battles, but might also be used to suppress cannons.
Contrary to the Samara, the range will be significantly higher because we are not modifying a Brown Bess, and we're not using a shorter barrel. This means the enemy cannot attack us by sprinting Victoria-carriers through the firing range (as done with the Samara), and we will probably have more people armed with the Long-Range Rifle than they have with the Victoria.
And, for comparison, the other two rifle designs:
A breechloading rifle using a specially shaped round designed to engage the grooves when the pressure of the gunpowder pushes on the conical base. it is primed using a new percussion cap consisting of a stabilized mercury fulminatecoating, that when dtriggered directs a blast of hot gas and flame down a nipple igniting the powder charge.
The "Fast Action" Rifle mark one is, simply put, a brown bess musket with the breach removed and replaced with a section that, when a side-mounted knob on the breachblock is rotated the rearmost section of the barrel pops out, allowing the loading of its paper cartridge. The barrel section is then pushed down and the block is rotated back to its inital position.
The weapon is also rifled, and the munitions use soft lead so they can expand and fill the rifleing, aided by the shape of the cast rounds(which include a dimple in the base and a slightly pointed nose).