I will try to help as much as I can. I have a stainless Omega and have shot Pyrodex Select, Tripple Seven ffg, American Pioneer ffg, and Black Mag'3 powders using plastic sabot bullets. Some of the sabot bullet combinations load with some difficulty in the T/C barrels as they tend to be a little tighter than some of the imports but that also helps to make them deadly accurate. I got very good results with Pyrodex and Powerbelt bullets in 295gr. and 348gr. weights. I usually load from 80 to 100gr. of powder. I have not shot any 150gr. powder loads as I find no reason to use that much powder. I hunt elk and the 90gr. loads with Black Mag'3 and a 300gr. bullet shoot completely through and elk at 100 yards. I suspect you will not be able to get all the synthetic powders but Pyrodex will do quite well although it is very dirty and will require a swab between shots. Most use a spit patch and run it in then flip it over and run again. You may be able to reload after only one spit patch. I personally use a very wet patch with t/c #13 and then run a dry patch after. Pyrodex is very corrosive so the rifle must be cleaned well with hot soapy water after shooting and I lube the barrel with Ballistol although many use bore butter (which I do not recommend) and many use standard firearm lube which I think is OK if you do a real good job removing it before you shoot again. Petroleum oil seems to make a mess with black powder if you do not get all the oil out before shooting again. I have not seen a lot of plastic build up however I do not shoot a lot before cleaning the rifle. If many sabot/bullet combinations are run (like 30 to 50 without cleaning) it is possible some plastic may be left in the bore. There are shotgun cleaning chemicals specifically for plastic removal. Acetone will work but may be difficult to find and must be followed with other cleaners to get it out and also a protective oil as acetone will make the metal subject to rust as it removes all the oil also. The ascorbic acid based powders like:Black Mag'3, American Pioneer and Goex Pinnacle are much less corrosive to steel although they will attack brass. On an Omega that is not a big problem. Hope this helps. Forgot to address break in. I ran 200 passes in the bore with JB bore paste on a patch over a brass brush to speed up the break in process. You can shoot patched round balls as a break in or solid lead conicals to smooth up the bore. The plastic sabots will not do a decent job of smoothing the bore. The Omega bore is pretty well machined and mine was very smooth to start with but most will require a little break in.
