My .54 is just a flint Lyman GPR with a 32" GM smoothbore barrel fitted to it. So this is definitely a "smooth rifle" and not a fowler. Handling wise, think more like a heavy barreled slug gun (if thinking shotguns) or a rifle with no rifling in it, but it does have both front and rear sights like any other rifle. My loads are:
Light: 55grs FFFG, 3 cards, 3/4 oz #6 shot, 1 card
Heavy: 70 grs FFFg, 2 cards, 6" jute twine nest, 2 more cards, 1.5oz #6 shot, 1 card
PRB: 80grs FFFg, 4 cards, patched .527" ball
I have also been playing with a .515" RB mold I picked up and the load I use with it is 80grs FFFg, and then just the PRB as with any other rifle, skipping the cards. The reason for the cards with the .527" RB was that the patching is so thin that I couldn't find any kind of lube that was sufficient to prevent burn through with the flimsy patch. The .515" RB allows use of standard pillow ticking, so lube is no longer a problem. Accuracy is equal so I will probably stop using the .527"RB.
Just remember that the loads I listed are for MY gun, which has a full length straight octagon barrel that is 15/16" across the flats, so if you end up with a light fowler barrel on yours, it may not be a good idea (or safe) to directly copy them. As to turkey loads for this .54, I would trust the heavy load listed above out to about 25yards, and MAYBE to 30yds if everything felt perfect, but this gun is completely unchoked, so if you have any choke that should extend your range somewhat. I prefer the cylinder bore because I probably shoot more PRB than shot in mine. Don't laugh too hard, but I intend to use this .54 loaded with 80grs FFFg and the .515" PRB this year, and trust the gun to about 65 yds with this load on a turkey size target, but hoping to get quite a bit closer. You said you're in Texas also, so please check your regs for the county you intend to hunt. I am in Waco, McLennan County, and I am allowed to use a rifle during the fall season, but it is SHOTGUN ONLY for the spring season. Now the regs don't say anywhere that I have to use any set shot size, or weight of shot load, or that I even have to fire multiple projectiles out of my shotgun, so I can fire anything I want, as long as I fire it out of a shotgun. So I am legal to use a single PRB this spring. If I decide to use my 13ga, I will have one barrel loaded with #6 shot and the other with a .690" PRB. BTW, if you're ever this way and want to try mine, you're welcome to. And my 13ga loaded with 75grs FFFg and the .690" PRB, or the 65grs FFFg and 1oz of #6s recoils less than my 20ga Mossberg 500, but about the same as the same Mossberg when loaded up to 75gr FFFg and 1 7/8oz of #6s. Now the heavy shot load is above what the manufacturer recommended for mine, but it patterns well so I use it, but worked up slowly. So don't be scared of a larger bore if you decide the .54 is too small for you, after all, it is YOUR money and not anyone elses that you're spending.
If you pass through this way, let me know and I will meet you if my work schedule allows. They get kinda goofy at some times of the year, but I'll try.
Here's a couple old thread that I saved in my favorites for the lists of other shooters loads listed. I hope they help.
http://www.muzzleloadingforum.com/...t/1254027/hl/13ga+loads/fromsearch/1/#1254027
http://www.muzzleloadingforum.com/...t/1137116/hl/13ga+loads/fromsearch/1/#1137116