that bore looks like it has shot a lot of jacketed slugs sometime in its life. Those early 93's "old steel" barrels were made for cast slugs and jacketed speeds up the wear considerably.
marlin bores of that era have a reputation for being very generous in finished bore size, quality control in the barrel room didnt seem to be their strong point. With that point made & the wear in your barrel that group isnt actually that bad but you may be able to tightenit up by 1/2 with fatter slugs either by bigger mold or up-sizing your existing slugs with powder coating ( wont hurt/wear your bore anymore than already is . If your unfamiliar with PC, go down to the "cast bullet" forum
here is my 30 30 bore. its part of a video of the entire bore but i dont know how to post the video.anyway it was shooting hornady 150 grain bullets well a few years ago but when i couldnt get them i switched to speer which it wouldnt shoot well so i retired the rifle to my gunsafe and only decided to take it out with different ammo today.i used rusty wood .311 bullets made for marlin microgroove although my rifle is a 93 with conventional rifling
