i remember that lab test, a few bolts actually performed worse than the stock one.
for me, that sort of upgrade (powertube, bolt, etc) is an "only if the stock one breaks" sort of upgrade.

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Proud Canadian Baller
Kit: A5, camo job, polished internals, 14" Smart Parts Progressive barrel. Borrowed Opsgear G36 stock. 24oz CO2 w/ remote and slide check. Neat homemade sling. MORE TO COME
Vents Goggles and Multicam