I may get one,I know they are made to help stabelize slugs or sabots?,but are they a gimmick or do they tighten the groups?Any articles/test written or firsthand experience's? Thanks!

Yes. A friend did some experiments years a go .Most accurate - sabot in rifled barrel
Next sabot with rifled choke .
Next standard slug with rifled choke.
He commented that after using the rifled choke it had screwed tighter and was difficult to remove.

Hmmm,thats good,Thanks!!....anyone else?

i have threaded numerous smooth bore barrels for choke tubes. the tubes improve the accuracy of slugs over the smooth bore by a lot. not quite as accurate and consistant as a fully rifled barrel though.

Thanks,Guess I need one for my Benelli!