I know of one that failed after less than 100 rounds of factory LBC ammo, but that was probably a manufacturing defect. 6 years or so ago, I tracked down info on every broken bolt posted here or on ARF.com, and all but the one above had broken with handloads.
Almost always in these cases, its because there is a bad extension/bolt match, where the extension and bolt aren't square to each other,most often exacerbated by near max handloads.
There is no doubt that the bolt is weaker than the 5.56 bolt, it simply doesn't have as much metal in it.
Although your posted max loads are correct, that doesn't mean those are YOUR barrels max loads. Your barrel may not tolerate anything close to max, especially if there is a bad extension, which has been noted to be an issue in many situations.
Its been a while since we had a batch of broken bolts, and it would be interesting to know if both were from the same batch, which might indicate a heat treat issue.
Almost always in these cases, its because there is a bad extension/bolt match, where the extension and bolt aren't square to each other,most often exacerbated by near max handloads.
There is no doubt that the bolt is weaker than the 5.56 bolt, it simply doesn't have as much metal in it.
Although your posted max loads are correct, that doesn't mean those are YOUR barrels max loads. Your barrel may not tolerate anything close to max, especially if there is a bad extension, which has been noted to be an issue in many situations.
Its been a while since we had a batch of broken bolts, and it would be interesting to know if both were from the same batch, which might indicate a heat treat issue.
You seek escape from pain. We seek the achievement of happiness. You exist for the sake of avoiding punishment. We exist for the sake of earning rewards. Threats will not make us function; fear is not our incentive. It is not death that we wish to avoid, but life that we wish to live. - John Galt