I just purchased a 17S and it will not feed. I'm at a loss. I have two factory mags and I have tried three different ammo (including match grade). Both mags and all ammo does the same thing. When I release the bolt or rack the charging handle it doesn't go all the way forward. It normally goes about 3/4" short of all the way forward. When it does go all the way it will fire but will not cycle the next round. It is clean, not spotless but clean. Any ideas?