06-12-2013, 09:36 PM
Keep The Change Wrote:bwaites,
There are 2 types of 264 LBC bolts with different depths. I just bought one and it is 0.134" deep. I measured it this week.
Is it possible that the wrong type LBC bolt is being used?
That is a basic question and I'm certain this is not the case if LB looked at it, you would think the head spacing was checked with the old and new bolt.
Just thought I'd ask or raise that possibility.
Surely the 0.002" difference in depth from the Grendel Bolt to the LBC bolt would cause these issues. Correct?
There should be enough tolerance in the headspacing to accomodate this.....I think.
LBC itself uses the Grendel SAAMI standard bolt, unless something has changed. That is the the bolt with .136 face depth. (.134 is probably within the tolerance spec).
The .125 face depth bolts were a compromise that started when standard Grendel bolts were scarce. This whole "Type 1" vs. "Type 2" thing started because Black Hole Weaponry initially couldn't get .136 bolts and decided to chamber with the .125 face depth. When they started getting SAAMI bolts, they had to differentiate between the two, and started using the Type 1/2 nomenclature. The rim of the Grendel case is thicker than 5.56, and that extra depth allows a proper extractor geometry.
Some builders continue to use the .125 bolts, but thats because they can get them, not because they are optimal. I have no idea why ARPerformance chose to use that face depth, since there is a SAAMI standard, and someone is going to get hurt swapping bolts and not knowing. A .125 bolt won't close on a Grendel chamber, but a .136 will on a .125 chamber, and thats a lot of headspace difference.
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