In choosing a size of shot for a large bird like turkey, you first have to understand that if the gun you have ordered comes with a cylinder bore, ( ie. it has NO choke ) the range at which you can reiably take a turkey with a single shot is restricted to under 30 yards, and probably less than 25 yds.
That having been said, It is the weight of each pellet that transfer's energy, and not the velocity. You are not going to get 1300 fps out of a Black Powder shotgun unless you use a very unbalanced load, with lots of powder, and very little shot! So we don't recommend even trying to obtain the speed of modern shot shells.
I recommend #5 shot, but many people get good results using #6, and some use #4 shot. All have done extensive patterning of their guns and loads before settling on a load combination that works in their PARTICULAR gun. You are going to have to put in time on the patterning boards with your gun, no matter what recommendations we give you. Every gun is different. Every Shooter loads his gun differently, and I am not speaking only of components. Its often the loading technique of the shooter that determines what works for you, and not for me.
You need to know that Black powder loads in shotguns are measured in DRAMS. A dram is equal to 27.5 grains of black powder. Most shotguns of 20 gauge and larger work best with FFg powder, rather than the smaller FFFg powder. But try both. Some guns shoot FFFg powder better.
I found that using a good 1/8" card wad over the powder to seal the bore from the powder gases works the best in my gun. Others here use felt wads, and other kinds of materials. I tried the others, and fire my gun over a chronograph to see what was giving me consistent velocities, and settled on the card wad for my gun. Your gun may be different. The only way to know is to test it over a chronograph.
Read the V.M. Starr article in Bob Spenser's Black Powder notebook to get a good idea about what loads to use for what game.
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70 grains of powder is only 2.5 drams, which sounds like a light load until you check the boxes of 20 ga. shotgun shells at your local gun store and find out what " dram Equaivalent " loads they are selling in 20 ga. 65 grains is about a 2 1/4 dram load, and it is no slouch, either.
One of the old rules of thumb you will find mentioned here is, " much powder, poor patterns; less powder, better patterns." You will get a denser pattern using a lighter powder charge in relation to the volume of shot you use, than if you try to increase the velocity by adding more powder under the same volume of shot.
Lastly, if you review the posts, you will find recommendations for combinations of components, powder to shot, being 50:70, 50:80, meaning that if you use 50 grains of powder, you should use a 70 or 80 grain volume measure of shot. Others describe the proportions as 3:4, 3:5, 3:6 etc. Basically, you will find that you can maintain one powder charge and increase the number of pellets that pattern on your target by increasing the volume of shot you load in the gun. I don't know anyone personally who shoots a load that is twice the amount of shot by volume to the amount of powder, but there is probably someone out there who swears by such a load. If you are experimenting on your own, start with a 50/50 load, that is, an even volume of powder and shot, and then increase the amount of shot by 1/8 dram increments. That would be about 3.5 grain of powder as you make an adjustment to you powder measure. YOu can ov course increase the amount of shot in any kind of increments that you like, but I think you will find a load that patterns the best in your gun quickly by doing this kind of testing.
Eventually, you will want to get away from newspaper, or plain wrapping paper for your testing, and try your load on a Turkey target consisting of the head and neck of a turkey. You can actually find these on the internet to down load, and copy. You want to have a consistent pattern that will put a minimum of 5 to 10 pellets in the head and neck of the target, in order to insure a kill. Of course, only one pellet in the brain is needed to kill a turkey, but it is amazing to most turkey hunters how much punishment a turkey can take and still be flopping around, if you are lucky.
I like to recommend the larger sized shot becuase they carry enough energy at 25 and 30 yds to penetrate bone, and cartilage to reach the spine, or brain. At very close ranges, any shot will do that job. But when you get to 25 yards, and further, the shot that is 7 1/2 or smaller just runs out of gas to kill a turkey cleanly. Now, I have killed dove with #8 shot at 35 yds, but this is a much smaller bird, and that one bird was hit in the head by one pellet. Does the word, " luck " come to mind? It did to me that day! :rotf:
