Don't decap for my progressive loading. Seems to defeat the purpose of having a progressive in the first place. Dont believe it would make that much difference anyway with such short range rounds(.45 acp and .38special). I do tumble them capped though just so I dont run filthy stuff through my dies. I do decap .44mag and 357 and 45-70 before cleaning . I just wipe them off before I run them through the dies. But I shoot alot less rounds with those calibers.