From another thread (did not want to hijack it)

DannoBoone ask
"MikeCTX -- not to change the original subject, but what dies do you use for your
Tac 20? I have no problems with mine prior to fire-forming, but the cases become
very large for the full length Redding dies. The .20 Hornady neck die results in
terrible case run-out, resulting in mediocre groups. The pre fire formed rounds get
1/4" or less groups, if I do my part."

I use Redding FL die set (did not spring for one of the Type S dies) and Forester does not make a 20TAC die. Using Dakota/Lapua brass and have a no turn neck (.232) and so far having no issues. The neck is tight (and depending on the brass have given the neck a light turn). Might want to check the headspace on your fireformed cases and bump them back just a bit, .001 or .002. That seems to be what has helped me the most so far.

There are a few 20 Tactical shooters here, so hope some of them will stop by with their thoughts too!