Unlikely. Steyr changed their action lengths over the years; the rails that we produced were for the later production models of the Pro Hunter.
You will need to measure the screw hole spacing on your receiver between screws 2 & 3 (3 & 4 if you have a 6-hole receiver). Here are those spacings for the rails we produce. If your rifle does not match, we will not have a Picatinny rail option.
Short action 3" Long action 3.25" Magnum action 3.45"
That's correct, MPN: PXM252151 is the 20 MOA base.
The difference is cant. The PXM252151, 2nd upc, has a 20 MOA cant.
No, these rails are for magnum actions.
Yes, this will work with that rifle.
No, unfortunately it is not.
No, here are links to the Long Action variation of this rail in both 0 and 20 MOA:
https://www.opticsplanet.com/talley-picatinny-base-long-action.html?_iv_gun-model=steyr-pro-hunter-long-action
https://www.opticsplanet.com/talley-picatinny-base-long-action-20-moa.html?_iv_gun-model=steyr-pro-hunter-long-action20-moa
These should fit your Steyr Hunter Pro chambered in 300 Win Mag, as the inner hole spacing is 2.72".
The inner hole spacing is 2.72".