First thing, I am NOT an expert on the DE by any stretch. For some reason, it's almost impossible to find information on Red Dot sights used on the DE. I have now tried two; the Bushnell "First Strike" and the Burris "Fastfire III". Exhaustive testing? Nope. Actually buying one and shooting it, not simply repeating advertising or word of mouth? Yup.The First Strike was first up and it worked great for 16 rounds; thought I had it made. Round #17 cracked the glass, BUT it was still usable. Not real clear, obviously, but the dot was still there, and it shot to POA. Sent it in to Bushnell and got a card back about a week later saying that they'd received it and were waiting for a replacement. Excellent service IMHO.
After considerable research, decided to try the Burris. Installed it and fired a magazine, re-tightened the screw, shot another magazine, tightened the screw, another magazine, re-tighten, and yet again. Another magazine, and this time it held for the rest of the 50 rounds. Stayed sighted in, stayed put and no problems. Granted, that's only 50 rounds and also consider that my load is "only" 22.8 grains of H110 and the Berry .44 plated HP. Simply put, that's my limit and I will NOT shoot that load in my Super B Hunter. Once was enough on my arthritic shoulder and wrists. I have no idea how many shots it would/should take to consider it "good to go", but I'll keep plugging away at it and keep you posted, if anyone is interested.