10-15-2013, 06:45 PM
It seems to me that WB is treating the symptom, rather than addressing the cause. The Half moon marks mentioned are quite likely from extractor pull. This is consistent with a bolt that is unlocking early. The usual suspect in such a case is an over-gassed condition, which is a common occurrence in the Grendel. Increasing BCG mass will dampen the reaction to the high gas pressures, but it can come back to bite you, if you decide to try different loads. For the cost of the two H3's you can install a quality adjustable gas block, which would likely resolve the issue. This way, you don't increase the reciprocating mass, which is a win, in my book. The other principal advantage to the adjustable gas block is that it offers the capability of tuning virtually any load you care to feed your thunder stick.