Originally Posted by
farscott
The Flexi-Tab upgrade involves three parts, the lifter, the bolt carrier, and the bolt. The lifter has a notch shaped like a “U” on the bottom, the bolt carrier has side clearance cuts, and the bolt is notched at the bottom. The parts have been designed to allow such a jam to be cleared but do not prevent such a jam. In other words, you can still jam an 870 with these parts by short-stroking it. In the event that one does encounter a jam, it can be cleared by holding the forearm and slamming the buttstock on the ground. It may be possible to muscle the action open without slamming the stock on the ground, but my experience has shown that "grenading" the butt stock is the most consistent. That method, however, can crack or split a wood stock.
I cannot speak to the Mossberg guns, but the difference in carrier operation suggests to me that the same type of jam is not possible with the 500/590 guns.
As for 870 usage, training is a big deal, and I was taught to run the slide as hard as I can as I am not going to break it. And I also practice clearing the jam as it can also occur if a shell latch fails.