Yep, I would go with Thompson for a side lock.1. T/C is about the best all around with the Hawken being the most common. Lifetime warranty and mine happens to be vintage '76 and hasnt had issues to date.
One thing I didnt mention about the T/C Hawken was that its entirely possible (within stock inlet size limits) to get replaceable barrels so one can fling itty bitty .36 caliber to .54 cal slugs with a barrel swap. Futher Green Mt makes a drop ins with different twists so one can use sabots or RB depending. The stock TC barrel with its 1:48 twist is a good learning and general purpose but a 1:66 or 1:72 is better for RB and a 1:20 (or in that general area) is better for longer slugs-sabots.Yep, I would go with Thompson for a side lock.
For in-line I would go with the CVA optima pro.
It is the best bang for the buck and no quirks like a Knight and Hale, Remington 700, and some of the others.