I use a sizemaster to install the primers the first time. On This machine you can bottom out the primer. It has a bottom. The grabber and 9000 just float the hull in the priming station. It has no bottom to it. So it much more difficult to get that last bit of primer flush with the bottom of the hull. Lucky for me I started out reloading the 410's on the sizemaster. I picked up the 9000 because my demand for reloads grew over time. I have to do the same thing on the 28 ga. STS's as well. If I want to use a Win. primer. Its a PITA to get the primers in them. Good Luck on reloading the 410 bore. As mentioned its worth it in the end. break em all jeffOr run your batch with win209 without powder or shot and inspect for primers sticking out of the hull a fraction.