I agree and disagree here, both from experience.
A: Repro rifle musket/rifle sights such as those that are factory standard on guns such as the Zoli, Euroarms, and Armi Sport offerings leave much to be desired. The notches are often much too wide, and the sights lack stability under recoil, etc. I am looking into getting a custom rear sight attached to my M1855 rifle musket for exactly this reason. I would talk to Lodgewood Mfg. in Whitewater, WI about getting better sights for your rifle- they have some excellent custom sights by Rich Cross, so I am told, and offer excellent gunsmithing services.
B: In my experience, I have had no difficulty attaining excellent accuracy with Minies out of a rack grade rifle musket. In my personal opinion, one must simply account for a different- but not more tedious- set of factors to attain good accuracy with a Minie ball. In fact, it may be as simple to say that what makes a good Minie makes a poor roundball. For example, a Minie ball capable of producing good accuracy must be made of nothing but soft lead- both for best terminal ballistics and for the purpose of best engaging the rifling. PRB, for its part (as it will never likely 'contact' the rifling, as it is similar to a saboted projectile when contained in a patch)can be made of much harded material of varying compositions.
Minies must be appropriately sized- which if you cast your own or have them made for you (as I do)is not difficult- to the bore of the rifle in question. Much like finding a pet load for a roundball gun, one must fiddle to find the right sizing for the Minie, as well as the most suitable style. My gun prefers most anything heavy sized to .002 under bore diameter. With a roundball gun, a similar process is used when determining proper patch/ball sizing combination.
Similar steps exist for the right lube, powder charge, wads (if any) and etc. It is not- in my opinion- any more difficult or some such, or even less likely to produce accuracy, when making loads for and using Minie balls.
For that matter, I did very well in a competition this weekend here in WI where I shot my rifle musket (crappy sights and all) against almost exclusively PRB shooters, placing 3rd in the prone buffalo 5-bull shoot (M-9 target) using a .576 Rapine 575-510 Minie on top of 45 grains of Goex 3F, under less than ideal conditions (it was raining, the prone rest was too low, and because of that, I was forced to shoot off of my collar bone- it hurts... :cursing: ). The point is, don't discount the Minie ball out of hand- it's a different road, but we all know what Robert Frost had to say about "diverging paths" and so on. :wink:
Just my 3 cents' worth, and sorry for the hijack.
-Chris