I've been playing with this one with interesting results. Many years (decades, actually) ago I had a British rifle in 360 2 1/4 and a Sempert and Kreighoff in 9.3x57R(360) and the proper 200 grainish bullets were not generally available. I had a Lyman 366408 mould which is 250 grains and a gunsmith friend undertook the task to reduce it in weight. Suffice it to say it was quite an effort and the result came out at more like 175 grains. Well, those rifles are long gone but a new one showed up. The 175 grain bullet shot surprisingly well but I thought the original 200 grain might do better. Accurate moulds offers several .366 diameter bullets and I picked a 200 grain plain base to try.  The dual cavity mould casts well and to spec. I tried a couple of loads that had shot well with the 175 grainers and ended up with a 1.8 inch group at 100 yards with the iron barrel sights and my old eyes. At this point I have to admit that this single shot hammer rifle is attached to a single shot hammer shotgun - it is a Swedish Husqvarna cape gun on a Lefaucheux action. Perhaps it is no wonder that this same gun was made from 1895 to the 1940s. If it ain't broke, don't fix it. The Swedes didn't and I'm sure it served them well.

You probably know about this site but there are some loads for your cape gun. Nice gun you have!

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Now that I have a 33  I thought I might expand on how I load for it and the 17C for your edification and amusement (probably more for the amusement of a lot of you!). The bullet I'm loading is from Accurate mold 368196B and is cast in 1 to 20. It is sized to .366 and lubed with Javelina. The brass is DWM 9.3x72R cut to 57mm and annealed. It is minimally sized in an RCBS 9.3x72R die 'cause I had that set on hand. After seating a Federal large pistol match primer the neck is expanded with a Lyman 9.3 M die just enough to be able to start the bullet. I'm using 13.5 grains of SR 4759 dropped from my old RCBS Uniflow powder measure (with 4759 you must use the large throated spout!) with the micrometer adjuster (one of the best gadgets I ever got) set to 381 (YMMV). I visually inspect the loaded block with a small LED flashlight. Next an .060 Walters fiber wad is added flush with the top of the case and by habit I always seat the tapered side in the neck first. For seating I use an RCBS 38-55 die 'cause I had that set on hand, too.  I set the bullet straight in the M recess and run the ram up until the bullet is half seated then lower it slightly, turn the case about 180 degrees (another old habit) and finish the seating. My OAL is 71.1mm which puts the bullet just at the rifling. With a rolling block you need to be sure the cartridge seats easily so that the block fully closes so the hammer won't drag on it and change the blow given to the firing pin. Aim and fire. That's about it.

Thanks for the update! Wondered how the 33 was doing for you, and if you'd been shooting it much? Mine has been sitting, as I continue to debate the tang sight holes. I'm sure I'll eventually do it, just tough to start putting holes in the tang!

I would use just a bit more powder, a magnum rifle primer, and a reasonable crimp on the bullet. No wads or anything else in the case. I would also try a harder, slightly bigger, bullet. 
Your vertically stringing group just begs for better ignition and more pressure. 

A nice day for testing at 200 yards yesterday but unfortunately my good eye didn't go along with the plan. I was using the ASSRA 200 yard targets with the orange center and may have to dig out the black center ones for increased contrast. 10 shot results were not great but were able to show that the 200 grain bullet is tipping a bit at that distance with the 5744 and 4198 loads that I had. I'm a little leery of increasing the charges as the velocity is already in the range I want for Cowboy Silhouette. Also, the 5744 load looked like it might actually benefit from a slight reduction, tipping and all. However the 178 grain bullets from my old cut down Lyman 366408 with 5744 did well which leads me to have great hope for my nice 176 grain ones from my new Accurate mould once I get my brass polished and annealed. Interestingly the 178s and 200s shot to the same place on the target. I have a 9.3x57 Mauser that shoots 232, 250, 270 and 286 grain bullets all to the same point of aim. Maybe it is something about 9.3s.