The BPS and Ithaca 37 are indeed fine designs. Their major drawback as a basis for conversion to a magnum revolver round, as I see it, is their size. The design scale was predicated upon the dynamics of the 12 ga. shot cartridge. Thus the whole package is about twice as big as it needs to be. IMO, this would make the resulting conversion something along the lines of my Lee-Enfield .22 LR training rifle: an interesting curiousity, but of little practical value when compared to other designs scaled to the cartridge. Given the choice between lugging a 9 lb, 48 " .22 or a 5 1/2 lb, 37" one that shoots as well or better, which would you buy?
The Timberwolf was basically a revised and much-downscaled Remington 870. Most of the revision not related to the size of the cartidge was to make it suitable to the much-higher operating pressures of the magnum revolver rounds and the resulting changes in stress loads on the mechanism.
The result was a 5 1/2 lb carbine with superb handling characteristics and reasonable power in a very compact package.
There are some areas where the IMI design and marketing folks missed their mark badly, again IMO:
The inclusion of the integral optical sight mount to the receiver. It's hell-for-strong, but it compromises carrying handiness at the natural balance point and looks incongruous. Drilling and tapping the receiver for a conventional base and provision for mounting a receiver sight would've been a better way to go. I don't know many knowledgeable shooters who routinely mount optical sights on what're basically short-range utility or defensive arms.
The action must be open to load cartridges. While not really a factor in a field gun, it's a real handicap for an LEO/defensive carbine role. This one really killed them at a time when many LEAs still used .357 revolvers as a service sidearm. It otherwise would've been an almost ideal patrol carbine option with minimal cross-training issues to deal with.
Cost. Maybe the real biggie here. SRP for the Timberwolf was almost 50% more than competing lever action designs in the same general market segment. Most of the people who comprise that segment, as you pointed out, are looking for a "companion" carbine that uses the same ammunition as their sidearm. I'd bet that the vast majority of those to whom this concept most appeals own just the one centerfire handgun. Let's face it: most of the firearms owners in this country have perhaps a single .22 rifle or handgun, a shotgun, and maybe a centerfire "deer" rifle and/or an "all-purpose" centerfire handgun. They shoot them only occasionally and want the most seemingly cost-effective option available within their budgets.
When the practical factors of accuracy, magazine capacity, dimensional criteria, "handiness", etc. are comparable, action type becomes almost irrelevant to most of them when weighed with perceived-value. "If the Marlin will do the same job for $100 less, why should I spend the extra money just to get a pump?"
While I personally agree with you that there really should be a market out there for a slick, handy, ambidextrous pump-action carbine chambered for magnum revolver cartridges, I'm afraid that we're members of a very small niche in a shrinking global market. The capital investment in design, R&D, CNC tooling and programming, marketing and distribution for commercial production of such a product would be immense.
While I don't have the business savvy or the hard data to calculate how many units at what price it would take to hit the "break-even" point, the lack of interest on the part of those in a position to fill that niche inclines me to think that it wouldn't fly on the mass market level.
On the other hand, if you can come up with a design with the right combination of market appeal and practicality of manufacture to attract enough venture capital for a custom or semi-custom outfit to get involved.....
they never make anything I want...
