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Your extractor is grinding against the Inside Diameter of the 2 o'clock barrel extension lug, and you can clearly see the interference.
Bill Alexander said this was one of the issues he encountered when setting up production specs for .50 Beowulf and 6.5 Grendel, since we are trying to get an articulating bolt/extractor/barrel extension profile meant for the smaller case head of the 5.56 to work with a larger case head.
Things that would never show up with a 5.56 rifle even with tolerances going out of a certain range, like they do when heat-treating the extensions after the feed ramps are broached, will show up for larger case head cartridges if you don't control the processes and tolerances more closely.
In the case of the larger case head cartridges from a production standpoint, you have to make sure that the inner diameter of the barrel extension lugs does not waver on you with the heat treat outside of a very tight range. This is something the home builder can't really control and does not even have the tooling to measure.
Extractor snap-over during going into battery is part of the dynamic mechanical engineering that gets overlooked in a market where people have struggled to even correctly name the static dimensional differences on Grendel bolts, chambers, etc. One of the biggest enemies to achieving smooth snap-over is the presence of the O ring around the extractor spring. There is already a buffer inside the extractor spring meant to assist consistent spring tension under full auto fire. The O ring was added as a band-aid after SOCOM was having FTExtract malfs with M4A1s and KAC QD suppressors, as well as Mk.18s running suppressed.
The AR15 should operate smoothly within the ideal cyclic rate range with a relaxed extractor, and not need an O Ring to help with extraction on guns that are out of timing/extracting early during residual case pressure/obturation in the chamber. Those issues should be addressed at the source (gas system).
Bill Alexander said this was one of the issues he encountered when setting up production specs for .50 Beowulf and 6.5 Grendel, since we are trying to get an articulating bolt/extractor/barrel extension profile meant for the smaller case head of the 5.56 to work with a larger case head.
Things that would never show up with a 5.56 rifle even with tolerances going out of a certain range, like they do when heat-treating the extensions after the feed ramps are broached, will show up for larger case head cartridges if you don't control the processes and tolerances more closely.
In the case of the larger case head cartridges from a production standpoint, you have to make sure that the inner diameter of the barrel extension lugs does not waver on you with the heat treat outside of a very tight range. This is something the home builder can't really control and does not even have the tooling to measure.
Extractor snap-over during going into battery is part of the dynamic mechanical engineering that gets overlooked in a market where people have struggled to even correctly name the static dimensional differences on Grendel bolts, chambers, etc. One of the biggest enemies to achieving smooth snap-over is the presence of the O ring around the extractor spring. There is already a buffer inside the extractor spring meant to assist consistent spring tension under full auto fire. The O ring was added as a band-aid after SOCOM was having FTExtract malfs with M4A1s and KAC QD suppressors, as well as Mk.18s running suppressed.
The AR15 should operate smoothly within the ideal cyclic rate range with a relaxed extractor, and not need an O Ring to help with extraction on guns that are out of timing/extracting early during residual case pressure/obturation in the chamber. Those issues should be addressed at the source (gas system).
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