These are built to work with actions tapped for 8-40 screws. I believe your Bergara is as well but I would recommend checking with that manufacture.
Yes. You will need to use the short action NightForce One Piece Rifle Scope Base (MPN:A146). It will include the required hardware to mount to your receiver.
I would recommend using the Evolution Gun Works Picatinny Scope Mount for Thompson Center short action rifles, which can be found by using the link below:
https://www.opticsplanet.com/egw-thompson-center-encore-picatinny-rail-scope-mount.html?_iv_action-length=short-action
Please email us at techsales@opticsplanet.com with details of your rifle so we can further assist you.
Yes, this rail should fit the Bergara HMR Pro.
While the Mauser M18 uses Remington 700 mounts, these rails specifically will not fit because they are drilled and tapped for #8-40 screws and standard Remington 700 mounts are drilled and tapped for #6-48 hardware.
All of these rails come with #8-40 screws.