I've been trying to figure out if these are 2 separate conversion kits, or if the Achtisson is a modified Ceiner design, so what's the story? Do they use the same mags?

Atchisson is the original, has a rectangular fire pin face, like a 10/22. The Ceiner is basically an Atchisson, but has a round fire pin.

JAC bought out Atchisson, and resumed manufacture under his name, with a few changes. I do have the Atchisson, needs main spring, weak from age, and same for the Mag spring.

I found it at a garage sale back in '87 I think, don't think I paid over $15-20 for it, came with a 30 round mag. I think the fella had passed, and family was selling all his misc and reloading stuff in the garage sale.