I might have a line on a Brno 21 barrelled action in 7x57 (stock cracked badly). What would it be worth as a barrelled action and how tough will it be to find a stock that it can be put into (original or otherwise)?
I'd be looking to change out the bolt handle and go with a single (adjustable) trigger, and possibly switch the safety for a model 70 style.
I think the triggerguard makes it a bit tougher to drop into another stock and being a small ring does complicate the task.

I do not know what the market value is for such a barreled action, but I know that here in the US I would gladly pay at least $500.00, if it is the double square bridge action, and if the bore is excellent. Maybe even north of $600.00, that is a desirable cartridge.

The value in British Columbia may be somewhat less, however, I think there are more of them up there.

There are a number of used small ring sporter stocks out there, I see them on Ebay, and any standard M98 bottom metal should fit, if you are going to use a Timney or similar trigger, you might as well replace the bottom metal, as well, IMO.

Re. the price, maybe this will give you an idea of what someone thinks those rifles are worth:

https://ssaagunsales.com/listing/16662

well .. man, these are worth a ton more in original condition/fittings .. if you can get it cheap, i would strongly suggest having the stock patched up and duplicated .. .. but please don't bubba / model 70 a m21 -- these are worth the effort of getting a set of rings fitted and duplicating the stock

I HAVE A VERY NICE HALF STOCK FOR THE LONGER BARREL VERSION, BUT IT SOUNDS LIKE THAT WITH THE ALTERATIONS YOU ARE PLANNING, THAT YOU WOULD WANT TO REPLACE THE DOUBLE SET BOTTOM METAL AND THEREFORE WOULD NEED A CUSTOM MADE STOCK. I would be interested in the safety shroud and bottom metal should you choose to replace.

I am not familiar with a 7X57 caliber ZKK 691. All the ones I have seen have magazines designed for .243/.308 Winchester size cartridges. I would think some alteration would be required for a 7X57 to work properly through the magazine.

Pat-I HAVE one done up as you describe, bought it from you circa 2009. Mitch and Martini's did all the work and Terry of Reliable rechambered it to 280 Rem.

Shoots superbly and is a gorgeous piece one of many I am now selling due to age and FAR too many guns still.