Here in the UK the musketoon doesn't feature a great deal.
However we do have with the Muzzle Loaders Association of Great Britain, National Rifle Championship matches at 200, 300, 500 and 600 yards for Enfield rifles. A club I am in also shoots an aggregate match for Enfields (15 shots at each distance) at 600 and 800 yards. All these events are fired prone with only a two point military sling for support.
By far the most commony used rifle is the 2-band Enfield, and a good mix of original and repro will be seen on the range. The P.58 Naval Rifle and later Short Rifles with their heavy barrels have a good reputation for accuracy.
The P.53 (three-bander) is seen on the ranges and can also perform well, but far more use the short rifle. Besides the heavier barrel the sights on the two-bander are further away from the shooter than on the three-bander. This for many gives a better sight picture.
Is there much long range shooting competition with Enfields in the US?
David