Personally, I PREFER open hammer SXS's. I hunt grouse with them while my "hammerless" guns have tea parties with my other safe queens. There are several reasons I like them, but the biggest reasons are:
- I can check whether I'm cocked or on safety without taking my eyes off my quarry
- I like the sight picture framed by the hammers on both sides
- repairs to sidelocks are easier than with boxlocks, and easier still with open hammers
- I like the way they look and feel
As already mentioned, Norinco and Baikal offer open hammer SXS's, as does CZ. All of those, though, are coach gun versions with barrels in the 20" range. Be alert if buying a Baikal - they have 2 versions. One of them is built with fully functional hammers. With the other, the hammers are simply cocking levers.
Baikal used to make a full-length open hammer SXS. The wood was common grade and the metal finish was average. While the action was smooth and positive, the wood to metal fit was very poor. The stocks were done in a blond finish. The 12 gauge version was sold under the TOZ-66 model designation, although there was an IZH model designation that escapes me right now. I LOVE THOSE BAIKALS!!!
I originally bought the 16 gauge model, which I immediately fell in love with. Shortly after buying it, I refinished the stocks with a darker brown finish, similar to what you'd expect to see on a Winchester. The work made a dramatic difference in the fit and the overall look of the piece. I've since purchased a 20 gauge model that will be refit and refinished to match the 16. And, I've been keeping my eye open for a 12 gauge. (Anybody got one for sale??

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The one thing they could have done that would have made these guns highly desirable would have been to include removable chokes. I guess that will have to be my next improvement. Still, even as they come out of the box, they're the only full length SXS hammergun that you're going to find that was built for nitro powders.
You can buy made-to-order hammer doubles from most of the premier gun makers, including British, Italian, and Spanish "best" gun makers, but the prices are out of reach for the average shooter ($20K and up). One of these days, I hope to take that plunge but, in the meantime, I'm really enjoying the days in the field with my Baikal hammer doubles.