I've got a 686P with the original black rubber grips and have an HKS 587-A speedloader. When I first tried it out it did hang up on the grip. Upon closer inspection, I noticed that there was a tapered end on the aluminum center shaft of the speedloader next to the little roll pin. That tapered end hit the cylinder locking pin and left the speedloader plastic body in a position where it interfered with the grip. So, I filed that extra 3/16" off the speedloader shaft and now it works much better. If you didn't know that the speedloader had the tapered shaft end you wouldn't be able to tell that it has been modified.

Just a thought...