the Savage platform is a great option and are quite DIY friendly , all the parts are available from Arrowhead. If you already have a donor action there would be cost saving there ( a large shank would be preferred but not necessary).
A converted .45-70 break action is another choice there are a...
My CVA Scout has a Bergara barrel on it and it came with a radial brake, looks similar to the one the OP posted. It should be able to spin off possibly with a little heat if loctite was used. FYI Bergara uses metric threads.
I haven't found anything that compares to the Lyman 525 home made slugs, and sure beats the cost of factory sabot slugs. It takes a little futzing to find what it likes but once you do you're golden. I limit my shot to just over 100 yrds cuz these are like flying bricks.
I'm using a Savage 210...
I have a 210 savage ( older model) it's a tack driver with my home rolled lyman 525 slugs. Recoil was brutal , I filled the butstock with silicone caulking in layers and it really helped with absorbing recoil.
love these guns.
For that application you could use a CF large shank Savage action and get a .45 cal Brux barrel bolt nose and breech plug from Arrowhead Sporting goods. This has been a DYI for quite a few guys. Get yourself an action wrench and barrel vise to set proper headspace and swap out with a .50 cal...
Remington doesn't typically use a barrel nut so headspacing will be a little more difficult.
Your best bet will be to contact either of the two above mentioned suppliers and get pricing/info for DYI or have it done by them and compare. They do provide everything necessary for a complete...