I am new here so first thanks for the any advise in advance. I picked up a used New England Arms 12 GA Semi Auto and found that the bolt will not stay back if gun is jossled in any way . Just shouldering it as though you were ready to shoot will let the bolt jump forward. I have 2 other semi auto shot guns, a Montefeltro 20ga and Charles Daly 20ga and neither have that issue. I plan to next download a manual for this and a sanitize cleaning even though it looks clean.