DaveHH,
" BQ says that most all bolt failures are caused by problems with that left side slot. " I believe he posted something like this on CMPicon a while back.
I do not see how that can be true. The left lug does not take any load. It is a safety catch if the right lug breaks. If you check the drawings and add up the tolerances, the left lug is to be 0.001" +0.003" farther back than the right lug. The location of the right lug is 1.191" +.002".
Also a GI test bolt only has a right lug. I am sure if you had a receiver that was perfect on the minimum side and the left lug took some load, that would really help the bolt. But designed to do that does not seem to be the case.