Maybe I'm the only one who has experienced problems with the Contender action “popping open,” but I doubt it.   OK, so maybe I have been known to load a little hot.  :fire Anyway, there are several things that can contribute to the action popping open and several things you can do to reduce it (you'll never eliminate it, it's a inherent design weakness).   One of the improvements is a stiffer bolt spring.  I'm referring to the spring that pushes on the locking lugs. Here's a comparison of the OEM spring vs. an Eagle Arms spring vs. a>the spring rate formula.<list=1><*>Eagle Arms -- 0.032” wire thickness, 17 lb/in, 8.7 lb max load.<*>TC -- 0.036” wire thickness, 42 lb/in, 12 lb max load<*>Wolff -- 0.038” wire thickness, 53 lb/in, 14 lb max load. <*>Bellm -- 0.044” wire thickness, 130 lb/in, 20 lb max load. The actual force applied to the locking lugs will also depend on the spring preload -- i.e. the Wolff spring has more preload than the Bellm spring because I cut my Wolff spring longer than the Bellm.    I didn't go to the trouble to calculate the preload for each spring, so I can't give you a number for the actual force on the locking lugs.    My seat of the pants impression is that the Wolff spring is a tiny bit harder to open than the TC spring, and the Bellm spring is a tiny bit harder to open than the Wolff spring. The Eagle Arms spring is definitely too weak.  If you have an Eagle Arms stub I recommend upgrading to the Bellm spring.