I've taken apart and put back together countless side locks, both percussion and flint. They all operate basically the same but the new locks, as well as the TCs use coil springs instead of the more traditional leaf spring. The first thing that I would do is remove the lock, give a look over to see if you can physically see a cause in the lock itself for a heavy pull. While it's out, give it a good cleaning and then cycle it a few times paying attention to just how much pressure it takes to release the sear from the full chocolate chip cookie notch. This and a little lubrication on moving parts and contact points sometimes is all it needs. I saw a lock on ebay that had the little plunger that bears on the top of the sear frozen. Something like this could definitely effect the trigger pull. Check also, while the lock is out, the trigger and that it is moving freely in the stock. If all this appears ok, then the problem is likely with the sear/tumbler engagement. To address this will require disassembly of the lock and polishing or adjusting of these parts. I hope this helps and let me know if you figure it out.
