TOTW has T/C style breechplugs properly threaded to fit GM barrels. Just get a barrel and breechplug, install your own underlug, rib and sights. For a few hours work you have a properly breeched barrel for considerably less money than the "drop-ins" and you can get a greater variety of calibers as well. I've put GM barrels on several T/C, Lyman, Traditions and Pedersoli rifles and it really is not difficult. I'd never buy a "drop-in" as you pay for sights I'd throw away, a ramrod I'd also throw away and blueing I'd strip off to brown. I'd rather spend less and get more by putting in a little DIY time.