For an initial cleaning in order to get any packing oils/greases out of the rifle it won't hurt a thing to use a standard solvent like Hoppes, Shooter's Choice, etc to get it all clean. THEN I would swab the bore with de-natured alcohol to remove any petroleum residue before shooting it the first time. Petroleum residue & black powder residue can gum up, which is why people caution against using non-natural products................but for the initial receiving cleaning, you want to remove any packing residue as well.

After that, I use a 50/50 mix of Simple Green & water for cleaning after shooting, and I use a CLP product (FP-10 or Mili-tec) for preservation after cleaning. But I ALWAYS swab the bore with de-natured alcohol before shooting to make sure no petroleum residue is in the bore when I shoot.

Your load ought to work well out of this new rifle, though I might suggest trying the 300gr Shockwaves/SSTs as well..................they give me GREAT accuracy out of my Knight.

As far as bore prep/break-in goes.....................I recommend working 6 to 10 patches of a bore paste like J-Bs, Flitz, Iosso, etc through it before shooting. This will knock down any rough edges in the bore - which is what break-in is supposed to do, and what plastic sabots will never do. A lot of folks have a problem with this; but I know doing so, made my Knight and a cap & ball revolver much better shooters. If you had more time, you could do the same thing by firing a couple dozen lead conicals or patched round balls thru the gun.....................but the season is upon us and the paste will NOT hurt.