Anyone know of a side lock, in line ML. I am nostalgic and love my old sidelocks, but it would be nice to be able to use pyrodex pellets instead of powder.

A side lock inline would be hard to find. As close as you can get is a Thompson Center Firestorm or a Traditions PA Pellet.

These rifles do have a side lock which works the ignition system. They both also have a breech plug that can be removed for easy cleaning. Also they are both "advertised" able to shoot pellets. A lot of times shooters discover after the purchase that they get better luck shooting loose powder or they need to duplex the pellets.

I also have a T.C. Black Mountain Magnum side lock that can shoot pellets. I never have done it, but it is rated for pellets. (maybe I will try a shot or two). The breech plug does not come out. But it is a sidelock.

There are also rifles that work off a hammer system in direct line to the breech. Many of these will not shoot pellets though. In order to consistently shoot pellets, a hot ignition in needed. That would be a 209 primer or musket cap at the least.

If you build an underhammer right you can have a traditional gun that will do it all the only limitation is barrel twist. Lee

compadre - I believe you have your terms mixed up. A sidelock has the lock on the side of the barrel and is usually flintlock or percussion.
An inline has an ignition system which is 'in line' with the barrel. Usually ignition is from a 209 primer but there are other sources used also.
But Cayugad has stated what sidelocks are manufactured which can use pellets.

Why not just shoot powder???