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Developing Loads for Muzzle Loading Shotguns (Part 2)

posted May 23, 2010, 5:01 AM by Peter Lucas   [ updated Dec 17, 2012, 9:23 AM ]

    Part 2 of this Article deals primarily with developing a "heavy" load which is intended for hunting medium to large birds.   As discussed in Part 1, the light "equal volume" loads will generally produce both acceptable velocities and good patterns in most muzzle loading  guns. For example in a twelve gauge gun, a 1oz. load with an equal volume of black powder (approximately 68 grains) will produce velocities of approximately 1100 feet per second.  Heavy loads with equal volume of powder and shot, however, will generally produce inadequate velocities for hunting. A load with 1 1/4 oz of shot with an equal volume of black powder (approximately 82 grains) will produce velocities of approximately only 920 feet per second.  The obvious solution to the inadequate velocities of these heavier loads, is to increase the amount of powder.  The problem is the effect which increasing the powder charge have on pattern density.

   The almost universally true rule of thumb is that any change in ratio from equal volume loading will affect the pattern. Shooting more powder than shot will, in most guns, will tend to decrease pattern density.  Conversely, using less powder than shot, by volume, will tend to increase pattern density.  There is also one very large caveat to this rule, as you increase the amount of powder, at some point you are going to produce patterns with a dough-nut hoe in the center.


    Normal shotgun patterns will have a bell shaped distribution of shot in the pattern. That is to say that on average the pellet density in the center of the pattern is greater than at the edges of the pattern. The average pellet density gets progressively less dense as distance from the center of the pattern increases. The top illustration on the right shows the typical bell shaped distribution of shot. The greatest density of pellets is in the center of the pattern with increasing lower pellet density as you move towards the edges of the pattern.  The lower pattern on the right illustrates the classic “dough-nut hole” pattern.


    The two shotgun patterns reproduced on the right illustrate two important points about patterning. First, as you increase the powder charge in relation to the shot charge, you are likely to encounter a situation where the wads are blown through the shot pattern leaving a void in the center of the pattern.  Second, it is important to shot a sufficient number of shots and average the results when testing new loads. Both patterns were fired with exactly the same load from the same gun. In this case both patterns were fired with a Pedersoli SxS with improved cylinder choke tubes. The load was 3 drams of Pyrodex with 1 1/8 ounces of number 9 shot. The wad column consisted of two felt wads over the powder and one thin cardboard over the shot. The “dough-nut hole” pattern did not occur until the fourth shot of the test string. Had I only fired one or two test patterns this load, the problem would not have been known. Generally, I shoot a minimum of five test loads and average the results in attempting to determine pattern density.


    When you encounter the “dough-nut hole”, conventional wisdom is to either slightly reduce the powder charge or slightly increase the shot charge.  This usually will solve the problem. Alternatively, modifying the wad column can also eliminate the "dough-nut hole."  There are a variety of competing theories regarding what changes should be made the wad column when dough-nut holes begin to appear.  I have had success eliminating dough-nut hole patterns by attempting to increase the quality of the gas seal between the powder and the shot.  This can be done is several ways; such as using using a felt wad below the nitro card or using two nitro cards as apposed only one.  Other suggestions include using several (four or more) over the shot cards rather than nitro cards.  Decreasing the thickness of any cushion wad sometime also helps.

    Another technique which increases pattern density and can help with dough-nut holes is the use of a buffer in the shot column.  The period books indicate that bone meal was used as a buffering agent as early as 1830.  Bone meal is still readily available at garden supply stores. Lead shot will tend to settle to out of a bone meal/lead mixture due to the dramatically different densities of bone meal and lead.  Consequently, it necessary to devise a method of loading which insures that the bone meal and lead are mixed when the gun is loaded. My method is to pour a small amount of bone meal down the bore first and then add the shot.  By agitating the gun prior to ramming home the over shot wad, the two components are mixed together.

    For guns that have interchangeable choke tubes, increasing the amount of choke constriction can also eliminate dougnut holes.  In the book The Mysteries of Shotgun Patterns by George G Oberfell, and Charles E Thompson, the authors argue that the choke constriction is not directly related to the production of dough-nut hole patterns.  Instead, the authors postulate that the blown or dough-nut hole patterns are the product of naturally patchy patterns produced by open chokes. My experience is to the contrary.  I have found that when dough-nut hole patterns appear increasing the choke constriction can help to normalize the pattern distribution as well as increase pattern density.   

    Finally, using a shot cup, either paper or plastic, will often eliminate dough-nut holes.

     Turning back to developing the hunting load, I start by selecting a powder charge which will produce velocities of at least 1100 feet per second. (Consult a reliable table of velocities if you do not have access to a chronograph.)  For hunting I generally use homemade felt wads, so I start with two felt wads over the powder and one felt wad over the shot as my wad combination. Assuming that you are not producing dough-nut hole patterns, it now only a matter of making sure that you have adequate pattern density.

    In selecting your load, pay attention to the maximum safe load recommended by your gun's manufacturer.  Some recommended loads from older sources are well beyond current manufacturer's recommended maximums.  An example comes from V.M. Starr's book "The Muzzle Loading Shotgun; Its care and use."  V.M. Star was a gunsmith in Eden, South Dakota and was considered to be one of the experts on muzzle loading shotguns.  His book was really more of a pamphlet at only 11 pages.  The entire text has been reproduced at http://castboolits.gunloads.com/showthread.php?t=2605   The book is undated, however,  I have a copy signed and dated by the author.  The date on the signature is 1954.  For a 12 gauge gun, Starr recommended a heavy load of 3 3/4 drams of Fg black powder and 1 1/4 of shot.  3 3/4 drams of black powder is approximately 102 grains of black powder.  This abov
e the manufacturer's recommended load for both the Pedersoli and Beretta shotguns.  So be careful about how much powder and shot you load in your gun!

    Since your velocity is going to be lower than most modern loads, for hunting I generally use slightly larger shot and greater pattern density as compared to a modern gun.   For early season pheasant hunting, in a modern gun I typically use a 1 1/4 ounces of Number Six Shot with an improved cylinder or light modified choke. With the muzzle loader I use 1 1/8 ounces of Four Shot, 90 grains of powder, and a modified choke.  I also tend to be more selective on the shots which I will take with the muzzle loader.  For late season pheasants, I put the muzzle loader away.

    Increasing pattern density is easy if you are shooting a gun with interchangeable choke tubes.  Low pattern density can usually be cured by simply using a tighter choke (just like a modern gun). 
In addition, using a tighter choke will sometimes eliminate the dough-nut holes from the pattern.  Using felt wads with tighter chokes can be a real advantage. Since felt wads are flexible and do not have a memory, they can be easy pressed through the constriction of a full choke. 

    If your gun does not have interchangeable choke tube, your are going to have to attempt to increase the pattern densities by changing the wad column.  Unfortunately,  every gun reacts differently to changes in wad columns.  However, changing the type of wad, adding a shot cup or tweaking the powder charge will frequently improve pattern density.  Finding a powder, wad and shot combination which works best in your gun is largely a matter of trial and error.  In addition, some guns will simply not produce adequate patterns with heavier loads.  In that case, go back to the lighter loads.  A one ounce load of Four Shot moving at 1100 feet per second will consistently kill pheasants as long as you are selective in your shots.



The pattern illustrated above has a typical bell shaped distribution of shot


Shotgun pattern with a “Dough-nut Hole”







 

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