I’m at a loss

[Mad Professor]

I bought a TC with a Mag Spark type primer adapter and found it was removable by a hex (Allen) wrench inserted down through the nipple.

This is correct. There's a hex shape in there and the appropriate sized tool should take it right out.

I have removed several of these by unscrewing them with an Allen wrench as was stated above.

Glad someone has current experience and/or remembered how they install

I bought one of those many moons ago. When I found out what a PITA it was I never ended up using it. It's sitting in the back of drawer someplace with other ML parts. I couldn't remember how it got tightened.

I didn't chuck it, as if for some reason the sources of #11 caps dry up, at least I'll still have 209s as an option.

I always carry a candle with me when hunting, and wax around the nipple/cap to keep out moisture.

 

[Omega Vision]

There is good reason why the former owner upgraded to a livelier spark system with this particular make / model.

I had one. You are going to need a hotter nipple and hotter caps. I also recommend real blackpowder.
FFF Goex is what I used and it would help this entry-level, factory-poor igniting rifle out the most.

I used to shoot the charge out every morning after a hunt and again every evening after a hunt. I paid $50 for this like-new gun because I saved it's life after my hunting partner almost wrapped this gun around a tree trunk after a hang-fire and miss of a nice eight point buck. So I reached for $50 in my wallet and he bought a T/C Encore the very next week.

Don't ever trust this rifle 100% to shoot correctly, unless you live in a dry climate. I live in the middle of the Great Lakes region and humidity soars here. BTW..... I sold this gun for $50 about 2-3 years later. I now only have one caplock these days and it's a 32" brassy, percussion wall hanger. All my others are modern, hidden igniters. My favorites are the T/C Omega / Knight Vision