Kim:

No, when doubles are regulated at the factory, they're fired in R-L order. It DOES sometimes make a difference in regulation when firing in reverse order, because you're reversing the barrel heating order that it was regulated with. With some rifles it makes no significant difference, but with others it sometimes does.

A few observations. The kind of double discharge that you mention is part of the learning curve for heavy caliber double rifles, and firing the left first is not a panacea. I see you have a Merkel. Merkels are regulated at the factory firing in normal R-L order, just like everybody else's, and it appears that maybe they're not fired L-R at all. I've seen several Merkels in recent years double discharge when the left was fired first due to burrs on the sears that gave no trouble when fired in normal order.

Further, one of the advantages of a double is instant selection of bullet type (soft in one barrel, solid in the other). To use that advantage, you may find a need to fire whatever is in the right first. If you can't fire either barrel first with no fear whatsoever of a double discharge, that option isn't available in front of game.

Personally, I'd avoid hunting with a double rifle that I felt the need to fire in a certain order to avoid a double discharge. The confidence just wouldn't be there for me. I much prefer to master the type sufficiently that the order simply doesn't matter. The answer is ridiculously simple: all you have to do is keep your trigger finger mounted on the front trigger through the recoil impulse when firing the right first. Most people learn to shoot with the front half of the pad of the first digit of the trigger finger on the trigger. For quite a few folks, that just doesn't work on double rifles, especially with hands that are wet, sweaty, or bloody, and a different technique is the only answer I know of. In my observations of others experiencing this problem though, it does seem a hard habit for many to break. Try placing the trigger in the crook of the first joint of the trigger finger. It won't matter if your hands are dipped in STP, your finger won't slip off.

As for stippling or chequering the front trigger, I suppose it might help some. I've shot quite a few DRs that had such treatment on the front trigger. It's a nice bell or whistle, but I've never noticed it make a difference. I've never had a problem with smooth triggers though.