I recently had an incident which literally made me feel sick to my stomach. Although my rifle was loaded I did not have a cap on it during the occurrence. My rifle is a pat# 4700499 and has what I consider two safeties, the standard thumb safety and the screw feature at the back of the bolt which prevents the bolt travel from striking the nipple when screwed in. I typically keep both safeties in safe position until I am in my stand then unscrew the bolt travel feature. When ready to fire I push off the thumb safety and fire. Recently what occurred was with the gun loaded but uncapped and the bolt screw uncrewed as I placed my thumb on the thumb safety, the bolt slammed forward. Had it been capped it would have fired. I again cocked the bolt and barely put back pressure on the thumb safety and again the bolt slammed forward on the uncapped nipple. There is approximately 1/16 " clearance between the safety arm and the stock in the off position. After carefully capping and discharging the rifle I removed the stock and saw the single screw that holds the trigger block assembly to the barrel had backed out 3 to 4 turns allowing the front of the block to drop and as there is no fastener or locking tang at the rear of the block the 1/16" gap was enough to allow the mechanism to drop far enough to release the bolt if any backward pressure were put on the thumb safety. I truly love my bighorn, have taken several nice bucks with it and will continue to use it. This post is not intended to generate design arguments or procedural arguments. I've hunted for 50 years, I'm also a degreed mechanical engineer. The fact is this happened to me and hence it can happened to others. I discovered the issue with an uncapped rifle and others may not. Of course I loc-tited the screw and made sure the mechanism works properly now and most likely will remove the stock often in the future to insure the block assembly is tight against the barrel. If you have a bighorn or a similar designed trigger block assembly remove the stock and inspect it. Feel free to share this post with anyone anywhere who may use a rifle with this design feature. It made me sick to think of what might have happened versus what did happen. Thank you.