I have 4 Leatherwood Malcolms: one of the long scopes which I just got (it came with a rifle and I've not used it yet), two 3X, 17" scopes and one 6X, 18" scope. The optics are very good. As noted, the mounts are not precision. However, the intended purpose/use for the scope comes into play. My 3 short Malcolms are all mounted on black powder cartrige rifles used for hunting. The mounts were sufficiently precise to allow for easy sighting in and they have held their zero. The scopes have not fogged up while hunting in the rain. I have been very happy with them.
I also have an MVA scope used for black powder cartridge sihouettes. It is far and away a better rig, especially the mounts. But this sport demands much precision.
For hunting and/or general shooting with a muzzleloader, the Chinese Malcolms are perfectly adequate. I've had absolutely no problems with them and the mounts have more than sufficient adjustment for normal ML ranges with roundball.
Note that the short Malcolms use a Unertl style mounting system whereas the long scope uses a Malcolm style mount. Either one will work for muzzleloaders.