Gun Jammed up Today - how concerned should I be

[TreeDoc]

How were you holding the gun, Fabs? Sounds silly but I have had people do this frequently with polymer framed guns. It's even happened to me with my Glock when single hand speed shooting. Magazine is low on weight so mass changes and the recoil operation does not function as advertised. Add in a marginally stiff hand hold and the recoil is absorbed even more and you end up with a short stroking slide and an FTE. Just one possibility.

Diliberately dump a magazine full down range while consciously maintaining a very stout grip on the gun and see what happens. It could be a function of the ammo not generating enough blow back due to mild charges in addition to my thoughts above. Cleaning might help but it's an H&K and should digest any crappy ammo dirty or not.