Military, full-stock style rifles generally use musket caps. The musket cap produces more than adequate ignition for the rifle. Other rifles fitted with nipples that use number-11 caps may obtain better ignition with magnum caps rather than the standard-strength cap. Magnum RWS caps are designated number 55, in contrast to the standard number 75 cap. CCI now provides a magnum number-11 cap that is readily available from most dealers.
Original British target rifles were furnished with platinum-lined nipples. The high pressure generated by the large powder load and heavy bullet rapidly erodes solid steel, stainless steel, Ampco alloy, and other materials normally used in round-ball-rifle nipples. Ceramic lined nipples were produced in Germany, and some shooters have used them with good results.
When the hole in the nipple enlarges, accuracy is lost and excessive gas is blown into the hammer recess. Locks with weak mainsprings may have the hammer blown back to full cock and/or even suffer lock damage. Thus, nipple hole size and the strength of the percussion cap are very important variables affecting accuracy. If the ignition of the powder is not consistent, the velocity of the bullet will vary and shots consequently will string up and down.
The author made platinum-lined nipples with a .032 inch diameter hole into the platinum. For most rifles this hole size is adequate.
The fit of the base of the nipple in the snail or drum is not hypercritical. To minimize the potential of corrosion in the threads through the leakage of combustion products, however, the base of the nipple can be filed or lap fitted much the same as if one were seating a valve. Finally, it should be noted that ignition also is affected by the design and shape of the drilled passages in the breech plug.
Keeping records of your shooting and sight settings is very important. Having to change sight settings three times during a 45-minute relay, as when shooting the NMLRA silhouette match, requires accurate records for each load you are using. Keep a small notebook in your shooting box. Record in it data about the bullet, powder load, percussion caps, ranges, sight settings, location, wind values, and any other values you deem pertinent for quick reference during a match. You will not be able to compete adequately without good, accurate records.
Consistent Support Position
Long-range muzzle loading rifles are notorious for being sensitive to variations in barrel support position. When resting the rifle on sand bags while shooting from a bench, the shooter may notice that the bullet strikes one place when the fore-end of the stock rests on the sandbag, and another place when the barrel is rested on the bag. Most often the best accuracy is attained if the fore-end is rested in the hand and the back of the hand is rested on the sandbag. When using cross-sticks, the barrel must ALWAYS be rested in the same location for each shot.
Butt Plate Drift
A major problem with the rifles fired from the prone position is slippage of the butt plate on the shoulder. The cure is to use contact cement to secure a piece of 80-or 100-grit sandpaper to the butt plate. But in any case, remember that the butt plate must be pulled tightly into the shoulder for each shot.