Our FX DRS Slugr Magazine Model... The DRS Slugr Magazine (22cal-12shot) is the same size/height as the OEM mag and will fit under any of the scope mounting options - dovetail, low or high pic rail adapters on BOTH the Standard DRS and Tactical version rifles. DRS Slugr mags can handle pellets and slugs up to 12.5mm/0.5"in length! That is in the 42gr range (22cal) depending on the brand of slugs! When you're done loading these mags, gently tap the mag on the bench to fully seat the slugs. That will assure they stay put until you chamber them.
We designed the DRS mags with a snug friction fit on the barrel to hold it in place. We oversized the grippers a bit to prevent a loose fit and to account for the tolerance we've seen between different rifle barrels and breech wells. You'll need to firmly pop the mag into the breech with your palm the first time. This will allow the grippers to conform to the barrel and after a couple insertions the fit will give a nice easy snap in and work great.