Smokepole has it right, rifle and rifled muskets were sighted to shoot high because the muzzle velocity is lower than with a smooth bore musket. They reach out with more accuracy than a smooth bore, but the trajectory is a rainbow.
Lost In Translation, How to convert a Repro Rifle Musket A True Minié System Rifle Musket. People who shoot any recent large bore mass produced rifle or rifled musket reproductions have a problem: the arm’s performance is erratic; some people get decent performance from their reproductions whereas others get pie plate sized groups at 25 yard/meters.
You ask yourself, why the wide variety of groups? There is a reason for this. Large bore rifle muskets in the 1850's and 1860's were set up according to systems, i.e., American, Burton, Minié, Wilkinson, Lorenz, Delvigne, etc. and these accuracy systems insured that rifled muzzle-loading muskets delivered accurate and effective fire out to 300 to 600 yards/meters. Modern manufacturers, to save time and money, have taken shortcuts in production which negate the effectiveness of many current reproductions, changing or eliminating many of the features that made these system arms so accurate.
You can fix the faults or have a qualified gunsmith correct these changes/defects and have an accurate large bore rifle. The majority of all current reproduction rifle muskets can give you a 1" to 4" group at 100 yards/meters if the following tips are followed. You might think 4" at 100 yards is not great but the accuracy standard for many modern assault rifles is worse, such as for the Russian AKM which does good to give 4"-6" at 100 meters.
Properly size your bullets, and keep proper quality control. Minié, Williams or Wilkinson balls should not be more than 0.002 inch under size for best results. Weight of the bullets must be consistent and the lead soft.
Have the right countersink on your ram rod head. All these rifles had countersinks in their ram rod heads that matched the nose of the service bullet. Tests that I did with Gardner and Improved Picket compression bullets showed ramming the bullet and one seating tap with a ram rod with an ill-fitting head decreased the bullet length by 10% and altered the balance. It's a simple matter to get the correct countersink on the ram rod though; all you need is a drill, 5mm or 7/32" HSS drill bit, 12.5mm or 1/2" Christmas tree rotary file, epoxy, a cast bullet, Elmer's glue (white or clear blue school glue), and a half hour’s time. First apply a thin coat of Elmer's glue to the nose of the bullet that you will use to shape the correct countersink and let the glue sit 30 minutes to dry. Second you use a drill, drill press, or a metal lathe and a 7/32" HSS drill bit to drill a guide hole. You will need to go 2/3rds of the way down the tulip head, or on an Enfield drill to the tool slot in the head. Apply a small amount of oil or tapping fluid to the drill bit to assist in the drilling.
Using the rotary file in the drill you create an over-sized countersink in the head of the ram rod. You need to again use some oil or tapping fluid to assist in the cutting action, afterward degrease with alcohol or acetone.
Mix a small amount of metal filled quick setting epoxy or epoxy putty such as JB Weld and put it into the countersink, then gently press the head of the bullet into the countersink, wiping away any excess epoxy with a vinegar soaked paper towel. You can also use acetone, i.e., regular nail polish remover to remove the excess.
After the epoxy or epoxy putty has set, gently tap the bullet and it will fall out of the ram rod (the dry glue acts as a release agent), and you have a perfect countersink that matches the bullet you are using. I often find that doing this halves the group size on repro rifles.
Use good lubricant. All the original lubricants are animal fat or soft grease. Use a proven soft lube like MCM, SPG, or if mixing a beeswax lube use animal fat like pig’s lard or beef tallow if possible as it has a higher melting and vaporization point than vegetable oils like Crisco. This keeps the lube “wetter” and the fouling softer and more is removed by the bullet when shooting.
Use the right load for your bullet. Use the system set up by the late Tony Bagdon to develop a load for your rifle methodically (see
http://www.n-ssa.org/NATIONAL/CONTRIB/bagdon.html .) Bullet skirt thickness varies between Minié designs. I recently sectioned a Lyman 575213 NS bullet and a Lee 575-500M and found that even though the bullets weighed and looked the same the cavity shapes and skirt thickness varied radically. A load that works for one may not work in the other.
Make sure your rifle is properly bedded. You can take off the barrel bands and gently tighten the tang screw; if the point of impact raises several centimeters or a few inches it is not bedded correctly. David Minshall's website Research Press has reprint of W.S. Curtis "Managing The Enfield" at
www.researchpress.co.uk/targets/musketry/enfieldmanagement.htm The rifle musket can be very accurate at long ranges, and can be very versatile on game. I know of one USIMLT member who took a 1500 pound bison at 50 yards with one shot with a M-1855 Harpers Ferry rifle with a 33" barrel using a Wilkinson Improved Picket Mk III bullet with a spine shot, and a 1400 lb. bison with a 54 caliber Wilkinson Improved Picket Mk III bullet from a Dixie Lorenz Jaeger. I also know of an N-SSA member using a M-1863 Zouave rifle that has taken several fairly large whitetail bucks at over 200 yards using a 58 caliber CSA Gardner bullet. I have already posted some of the ballistic data and write ups on for the bullets mentioned above.
Plastic cartridges are also available for the 54 & 58 caliber bullets which greatly help your reloading speed. I hope the information was helpful.
Best Regards:
Greg Edington