Colt OKs the Cobra and Agent for limited use with +P. How old is your gun? If it is an early one (the Cobra has been around since 1950) with the grip frame the same length as the grips themselves, it should be very limited. If it has the shorter Agent grip frame with a skinny barrel and unshrouded ejector rod (1966-72), or is a post-1972 version with the heavy barrel, shrouded ejector rod and shallow-sloping front sight, you have a little more leeway. BTW, I have a post-1972 Agent with the factory add-on hammer shroud, to which I added Eagle Secret Service grips. Although the juncture of the bottom of the hammer shroud and the grip frame stings my hand a bit when shooting, it is one of my favorite compact revolvers.
I agree about the sharp-shouldered wadcutter bullet shape being a good idea, but the target wadcutter load would be lucky to get 600 fps out of a two-inch barrel. I would think that would cancel out the advantages of the bullet shape. Get the velocity up, seating the bullet further out of the case if necessary, and it would work a lot better. It is also fine for the first load to carry in the gun, but would make an unsuitable reload, IMO, especially with speedloaders.
