I purchased 4 pre-assembled magazines for the Kriss Vector directly from the Kriss website and have had multiple feeding issues with them.
Issue 1 (affected only one magazine). Could not load more than 14 rounds into magazine. Taking the magazine apart revealed that the follower was catching on some excess plastic on the top of the lower magazine extension. I used a nail file to remove some material which corrected this problem.
Issue 2 (affected 3 magazines). Feeding failure when 15 rounds left in magazine. The follower would not advance until something would jar it loose, it would then snap up due to the spring tension. Usually ended up with an empty chamber and would have to use the charging handle to feed the next round. This issue is caused by the follower getting hung up when moving from the magazine extension to the original magazine. I dismantled the magazines and saw a small white mark in the plastic that indicated to be where the follower was catching. I used an exacto knife to remove some material to clear up the path for the follower. This cleared up this issue all together.
Issue 3 (affecting 3 magazines). I’m having a feed issue on the second to last round, every time, on 3 magazines. The second to last round is held slightly low causing it to get smashed between the feed ramp and the bolt. The projectile gets pushed further into the casing creating a stubby looking bullet (see photo below). I have dismantled the magazines and can’t find anything obvious blocking the follower. I talked with another Kriss Vector owner who recommended storing the magazines fully loaded to loosen up the spring a little bit. I’m giving it a shot, but don’t think that will do it. The local indoor range allows shooters to use pistol caliber carbines, so I’ll be heading over there again soon.
All mags working great at my last range trip. Ran all 4 mags 3 times each and didn’t have a single issue. I guess loosening the springs did the trick.