THIS IS ONLY MY OPINION AND MY EXPERIENCE. YOUR RESULTS MAY VARY. I have had a couple of BAD levers installed for about 6 months. Didn't really have any problems with and I personally like the mod quite a bit. But....after I have installed an Adam arms gas piston set and replaced the original upper receiver on my pistol, it developed a problem. During test firing of 100 rds at the range, every 6 to 8 rounds the bolt would lock on the stop. Hitting the Bad lever locked it back up and it would fire fine for another 6 to 8 rds. Well when I got back from the range I didn't have a chance to really monkey with it , so I thought about it instead. Monday I was talking to a friend and he said it is probably the Bad lever. I said I would look at it and check it out. This is what I found, and you may want to check yours: 1. Upon looking at the upper and lower fit up you can see a slight offset between the upper and lower just behind the forward take down pin. My factory bushmaster has it and the original upper on the pistol had the same slight offset in the fit towards the Left side of the rifle. 2. Upon looking at the Aero Precision upper I had just installed, it was more pronounced to the left. I took a closer look at the bolt stop and noticed it was developing a noticeable mark and groove near the right side of the stop inside the lower. 3. I disassembled the bad lever and started checking the fitment of the backing plate. The one that goes behind the Bolt Release. It didn't really appear to be much at first but I noticed I had to pull the Release away from receiver just a fuzz in order to slide the plate behind it. Ah-ha, problem found. 4. On inspection of my bushmaster which worked fine I notice the same marks just less pronounced. I took the lever off and checked the fitment of the backing plate behind the release. I had to move it a lot less but the release was not truly free of resistance. That probably explains the lighter marks on the bushmaster. Neither of the weapons have enough rounds on them to explain the marks. Conclusion / Solution: 1. The BAD Lever backing plate must slide behind the release with NO resistance. Two out of two had to be modified. 2. The original thickness of the lever and back plate when screwed together off the weapon is about .318 at the thick area and about .278 at the thin area near the screw. I had to reduce mine from .318 to .298 to achieve clearance with the AP upper. 3. In order to reduce this dimension you need to screw the two halves together. This it to reduce the ridge of the lever itself so it matches. Using a nice flat file or dremel reduce the thick area. Do it slowly as to not take off too much. Check the fitment of the backing plate to the receiver. Again it should be reduced until there is NO resistance. 4. Once you have the thickness down. Install the lever and check to make sure you have NO contact between the beveled area at the top of the lever backing plate and the receiver. Use step 3 to reduce this area until there is no contact. 5. Once you achieved clearance reinstall the bad lever with new loctite. Again this is just IMHO. There are a lot of guys here with a lot more experience than I.