Beeg; since my 219L was of the last year of manufacture, it has a groove mount. The later models were called 219L (for lever) since they have a side lever to open the action.
With the hornet, there is a lot of "meat" around the bore in the chamber area to mount a regular weaver type mount. I would look much farther for such mounts, rather than the old side mounts.
445 super....try that Jet for a while, but be prepared for case head separation. With that long taper on the case, it will never seize in the chamber, but rather tends to back out, flexing the case ...causing incipient head separation.
Three guns were chambered for the Jet...the Marlin 62, a Rem bolt action handgun and the H&R single shot.
The case separation situation caused Rem to go to the .221 fireball after only a couple years with the Jet.
Surprisingly, the Jet doesn't use the common .224 bullet.
You may have the rare individual that doesn't have case separation problems.. I hope you do!
Sorry!....don't mean to "throw cold water" on anything, just wanted to report some common info...
A good website for more info...<www.reloadbench.com