Our FX DRS Standard Magazine Models... We have two housing sizes for the DRS standard magazines. The smaller housing (22cal-12shot & 25cal-10shot) 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 in BOTH the Standard and Tactical DRS rifles. The larger mag housing (22cal-15shot & 25cal-12shot) will fit under medium dovetail rings and under the high pic rail adapter ONLY on the DRS standard rifle. The larger housing mags WILL NOT FIT the Tactical DRS rifle. Both of the DRS standard mags can handle pellets and slugs up to 10.4mm/0.41". That is in the 36gr range (22cal) depending on the brand of slugs!
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.