Re: A2 style sights
Any drum will work, if there are finer MOA ones, those might be nicer, but those numbers on there really don't mean anything. What we used to do is put tape on the drum and mark the ranges ourselves after we had enough data. You can laminate it too. You can set it up to start at 100 that way and go to 600+ with a regular 8/3 A2 sight. And you could do it in any caliber you like. We used to teach SDM's to do this.
I think I recall seeing one that was generic and designed to be filled in with your own data, but it was a loooong time ago. If they make one, Brownell's will be where to look.
Hope that helps some.