The big difference your seeing is that conicals are usually a slip fit. That means they are meant to load easy, and then expand into the rifling once fired. Fowling is not as big a problem to them as to say a sabot, although if you will swab between shots on conicals the groups will normally improve.

I shoot a 460 grain .503 diameter No Excuses conicals out of my Black Diamond XR.



This was done at 100 yard off shooting sticks without swabbing. As you can see the conicals hold a real good group. Off the bench rest I can make them do even better, but I hunt off these same pair of shooting sticks and was going to hunt open fields that night and wanted to double check the load. You can see where the sabot hit (which is what the rifle was loaded with prior to shooting the conicals.) it is that smaller hole to the right.

Many people who find a conical that shoots good out of their rifles stick with them for a number of reasons. They are slip fit, so they load easier. They normally are not so fowling sensative. They are usually heavier so you have more down range energy when you hit. And they are actually bigger round. Not by much, .45 caliber VS .50 but still. Plus your not fooling around with the sabots. Also conicals tend to behave better in hot weather when shooting VS the sabot which can play strange tricks when the barrels get hot. (anyone who shoots a lot in the summer knows this).

I guess it is all a matter of choice. I have some sabot loads that shoot great out of the Black Diamond XR also. It is just that when I hunt in certain places, I want to stick as much lead in them and through them as possible to get some blood moving and on the ground in the event they run off......