I found with my rifles they often pin them exactly at 5 rounds maybe a little less it's a pain in the ass but you need to depress the rounds in a magazine a bit more
That appears to be the case with mine. All the mags must of been pinned a little too tight. I tried a mag pinned from the floor plate and it works completely. Thanks.
The mags that came with the gun have that standard side rivet. My old mag has that long fin on the floor plate.




























