You would want the Medium height TRYBE Optics Advanced Scope Rings.
Yes, I would recommend Extra High Height Rings.
The medium height rings fit a Nikko Sterling 6-24x50 on your Bear Creek Arsenal BC-8
TRO-RR-DX73K-TROHERNG34M
The TRYBE Optics Advanced Scope Rings are made in Canada.
The TRYBE Optics Advanced Scope Rings are not compatible with 11mm dovetail rails. I would recommend the Hawke Sport Optics Tactical Dovetail Rings, found by using the link below:
https://www.opticsplanet.com/hawke-sport-optics-tactical-rings-dovetail-1inch-medium-2pc.html
I would recommend the extra high TRYBE Optics Advanced Scope Rings as they will provide a 1.5" centerline, which is enough to clear a 56mm objective lens on most bolt guns.
The TRYBE Optics Advanced Scope Rings will not fit the SAKO L61R Bases. You will need the bases at the link below and then the rings at the second link below.
https://www.opticsplanet.com/riflescope-mounts-and-bases.html?_iv_parent-gun-make=sako&_iv_parent-gun-model=sako-model-l61r
https://www.opticsplanet.com/talley-detachable-ring.html?_iv_tube-diameter=34-mm
The height of the TRYBE Optics Advanced Scope Rings are measured to the centerline of the rings.
To mount the NightForce NXS Tactical Riflescope - 5.5-22x50mm to a flat top chassis I recommend using the 1.25in high 30mm diameter TRYBE Optics Advanced Scope Rings. These are model number TROHERNG30XH.
I suggest you use the High 30mm TRYBE Optics Advanced Scope Rings.