First you purchase a used 700ML, there were over 100,000 sold so It won't be that difficult.
Next you throw away the barrel and stock or give them to someone that can use them
Then you purchase an after market custom barrel for smokeless in 45 caliber.
You then send all of the good stuff to a gun builder that is capable of bedding the action in a new stock, 3rd pillar, barrel install, breach plug head spacing, bolt nose modification, new recoil lug, etc, etc, etc.
Then you send the guy a check for a bunch of money and he sends you your completed gun
You shoot in the 2500 - 3000 FPS area,( you decide) with great accuracy and almost no cleanup required and very safe.
I have 2 savages MZ's where I have already done this custom 45 conversion. They shoot great, just looking for another project.
I am not the pioneer with these builds, just a follower of a bunch of guys that are much more gun build knowledgeable than me.