I posted a long time ago about having this problem. i got several replies and ideas, replaced some parts, which made it slightly better, but did not cure it. i am an A-1 grade procrastinator, so nothing ever happens fast here. it kept bugging me, so i kept looking at it. i finally decided to replace the locking lug. which i purchased, and was shipped to me. when i took it out of the package, i discovered that it was over sized, and was going to require fitting. THIS IS WHERE MOST PEOPLE SHOULD STOP, AND TAKE THE GUN AND PART TO A GUNSMITH! always trying to do things myself, both because i have had trouble with gunsmiths (and every other repair facility i have used) and because i am so damned fussy, that few can actually make me happy. i started by measuring my old block. i decided that i was going to keep the tolerances as tight as possible, so slow, stop and check was the order of the day. which actually turned out to be 3 days. i slowly hand lapped the width, until it would fit into the receiver. then i started on the thickness. and finally, i had to lap the taper, where the lug fits into the bolt. i kept everything to as close to zero clearance as possible, and still have things move. after i got everything to actually move, though very tightly. i used a new piece of brass, and plasti gauge (used to check clearances in automobile engines) to check and make sure i did not have alot of headspace clearance. it showed .002" clearance using this method. which i know is not the right way, but purchasing go, and no go gauges to use once seemd like an excersize in futility. so i took it out and shot it. on the first shot of every step, i held the gun away from my body, and pointed it into a soft sand bank about 20 yards in front of me. i started at the lowest load i could find (7.0g AA2 with a 350g cast bullet & fill) and shot 3 of those first. everything seemed to work fine, so i went to the next higher step, which was beginning load for trapdoor. all which worked fine, i kept increasing the load until i reached as hot as i have ever fired thru this gun, which rattle the teeth of my poor departed dad. the lever never even thought of popping open once. while i would not advocate everyone to run right out, and start filing, grinding, or even lapping (on an actual precision lapping plate) their own locking lug. IF you are very skilled, very mechanical, very patient, very careful, AND MOST OF ALL, VERY LUCKY, it can be done at home. but, for Average Joe, if your having troble with the lever popping open, i would suggest you take it to a QUALIFIED GUNSMITH, and have him look into this as a possible fix for your gun.