At the top end of small bores, but is anyone familiar with this rifle? I’m familiar with the old Herters and their U9 and J9 rifles and see that this rifle is basically a 98 Mauser.
https://www.theoutdoorstrader....-264-magnum.1890140/

I suspect it is basically the same rifle as the early Herters XK3 and was imported in the 1960's. The actions were mfg. by Zastava and bbl were provided by Heym. If it is what I suspect, it was also sold by Montgomery Ward as Model 720EHM and is an intermediate action opened up at the front for long cartridges.

o boy - many moons ago i had one like that- fn deluxe action (side safety) i think the barrel got shot out in a about 400 rds i'd put the value at something like 400 - if the barrel is any good

I don't think any were Belgian FN actions. As I recall Zastave had FN machinery used for the FN 1924 Intermediate actions and modified the actions to not include the thumbcut and generally had lever release floorplates, although the front of the trigger guard was similar to the original FN military action. What is the length between guard screws?

The bolt handle is definatly FN...but Id have to have the gun in hand to make a good guess.

The bolt handles on the Zastava look the same as FN- same curve, flat checkered bottom. These rifles were not Belgian FN's. However, the bottom metal is not the same as found on the Heym or MW Western Field 720 EHM based on the Zastava intermediate actions (at least those I've seen), altho the stock looks much the same.
Again, what is the distance between guard screws and is the bottom metal steel or alloy, is the bolt stop/ejector housing like a 98 Mauser box or is it like the Browning Mauser?
If it is a full length Mauser action, I would guess it is an early Mark X Zastava action. That would also explain the bottom metal, safety and bolt shroud, altho I'm not aware of FW Heym being involved in the assembly of any Mark X actions.