Sprinco USA AR 308 M4 Extension Tube XP Buffer Spring
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Extra Extra Power Buffer Spring. The Orange spring is much stouter than
the Red spring. The Orange buffer spring was originally engineered for
the demands presented by .308 / 6.5 CM / .260 Rem, etc., heavy BCG
carbine DPMS Pattern applications using standard 7" Depth M4 extension
tubes and short 2.5" buffers (Including aftermarket "heavy buffers") in
robustly gassed 16” - 18” ML gas carbine platforms, but has been proven
to be a requirement for tuning over gassed carbines of any equivalent
heavy calibers in AR-10 pattern tubes with 3.25" buffers or lesser
calibers (5.56, etc.).