Curl

I grew up using shotguns with hammers, several of them.

When hunting, ie when you expect to shoot, I carried both hammers cocked. I cocked each one separately with my right thumb on the 12 gauges. The hammers were two heavy to cock together. If one tried to cock both at once it is quite likely one may have "gotten away" from one perhaps firing the shotgun.

On a nifty little .410 both hammers could be cocked at the same time by the right thumb quite easily.

Have not used a double rifle with external hammers but the principle should be the same.

If you wait until the bird flies to cock it will be gone.

'Hammered' double rifles are real nostalgia but slower on a reload.