Davet

So, first post, after advice/suggestions please folks. Got an Umarex HK 416A5 (the full size, not Sportsline) and looking to expand number of mags I have beyond the hi-cap that came with it. Ideally I’m after adjustable lo/mid, lo or mid cap mags. Not bothered whether polymer or steel type. I picked up a Nuprol N Mag adjustable to try out. It fits but is very loose - a little bit of wiggling and it drops out. Any suggestions for mags that might fit the bill and be a more secure fit? Thanks…