Okay: I am going to assume the Fowler will not be choked. It also sounds like you are going to use it mainly to shoot birds, with shot, rather than using it with a ROUND BALL.
First, Read Bob Spenser's Black Powder Notebook, for information on shot loads. He has his own article at the top of his list, and in the second column at the bottom, is another article by V.M. Starr, who many consider the father of modern smoothbore and shotgun shooting. V.M. was one of those old masters who kept the practice of Jug Choking alive long enough for it to catch on with shooters in the modern age.
http://members.aye.net/~bspen/index.html
You are still going to have to measure the bore of the 20 gauge when it arrives. You need to know that its a .620, or .610, or .625, or whatever, before you order wads. You can use "20 gauge" wads if its .610, or .620, but if its .600, or .625 or bigger, you will want to get either the next smaller gauge wads or the next bigger gauge wads, respectively.
My 20 gauge barrel miked out at .627, almost 19 gauge, so I ended up buying 19 gauge wads. No big deal, but without the proper wads, particularly the OP wad, and the OS cards, my velocities and patterns(? :shocked2: :cursing: ) were both eratic, and well under what I had expected for the powder charge used.
Jim Rackham, a member here, bought a new 20 gauge Fowler, from member Mike Brooks, and worked up his loads using only OS cards. He puts in his powder charge, then 4 OS cards, with some lube between the #3 and #4 cards, then his shot charge, and then 2 OS cards. He pokes off-center holes in the cards, to let air pass through them, rather than turning edges as they are seated in the barrel. This stops the " dieseling" that new smoothbore shooters experiencing trying to get their wads down the barrel.
I go one step beyond, or different than Jim, and omit the grease between the 3rd and 4th cards, but use a greased cleaning patch on my jag when I seat the 2 OS cards on the shot charge. This:
(1)lubes the entire length of the barrel in front of the charge, protecting the bore from rusting during long waits while hunting. It also
(2)allows the wads and shot to slide over the bore, rather than rubbing against them, and leaving lead deposits in the barrel. And, of course, its there to
(3) soften the powder residue for easy cleaning between shots.
I am shooting a 70 grain charge of FFg powder and 1 oz. of #5 shot for shooting large birds, like pheasants, and for turkey, If I go. For dove and other small birds, I am using the same charge but #8 shot. If its a windy, blustery day, I will change to #7 1/2 shot for better patterns. I may also be reducing that powder charge down to 65 grains after I do some more patterning with the gun.
Because of some pictures posted today showing the improvement to patterns by using a shot buffer consisting of " Jiffy " brand corn mix, I am going to begin testing that buffer in my gun to see if I can't tighten up the patterns from my cylinder bore gun even more. If it works, I will mention it here, too.
Don't expect velocities similar to what is obtained using smokeless powder cartridges in choked barrels. You are not going to get those velocites, and high velocity tends to blow open the patterns quickly because of the lack of choke. To get killing power on a bird at 30 yards and beyond, with a BP shotgun of any kind, you have to use heavier shot sizes than you would with a modern gun. The larger shot pellets carry pellet energy longer and deliver it to the target well.
But, don't expect your gun to be a 45 or longer yardage gun. I have seen men using modern guns with extra full choke break targets-- and, yes-- shoot at pheasants out at 60 yards and longer, and occasionally bring one down-- But any cylinder bore BP shotgun or fowler should be considered a 25-30 yard gun MAX! You have to know your yardages, and you have to choose short range shots to kill game. Because of the shorter ranges, the larger shot sizes do very well, and the fewer pellets does not leave large holes in the patterns at these short yardage distance.
A Black Powder fowler should be patterned at 25 yards, then checked at 20 yards, and again at 30 yards to see what happens to the patterns at these distances. Inside 20 yards, your real problem is NOT blowing the bird into swiss cheese. ( I purpose hold a bit to one side or another to hit close birds with the side of my patterns, and not the center). ( Oh, if you do mangle a bird, they still make great "Stir-Fry Pheasant!" Don't throw the bird away.)
If you find a load that still patterns tight at 30 yards, go back to 35 yards and check the pattern there, also. Now, put a steel can out at that longest range, and fire a shot at it. See if the pellets are penetration the can, or just bounding off. If the pellets bounce off, I would reduce the yardage for that shot size until I find a distance where the shot penetrates the can. Or, of course, you move to a larger size shot.
For comparison, one oz of # 8 shot has 410 pellets in it; #7 1/2 Shot has 350 pellets; #6 shot has 225 pellets; and #5 shot has 170 pellets in the ounce.
The nice thing about shooting any ML shotgun or fowler, is that you can customize the load with each shot fired. For instance, for a 20 gauge, you can use 1 1/4 oz. and that will give you 212 pellets to fill your pattern almost as well as you get with that 1 oz of #6 shot.
PLEASE, don't try to make your 20 gauge fowler into some kind of magnum shotgun. Its not. :thumbsup:
