Originally Posted By AKzgalore:
I'm a little confused about the buffer spring differences—should any exist, that is—between that of the mil-spec AR-15 platform, and the loosely-defined LR-308 ensemble of parts. If you have a standard rifle-length extension tube, can you use a ".223" marked rifle buffer/action spring with a .308 upper? The ".308" marked springs I see are mostly all for A4 carbine-length extension tubes, not for the full length of a rifle-length tube...any clarifying distinctions possible here at all folks?
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No... you must use 308 length recoil springs and buffers with the longer 308 BCG.
I other words , the 308 BCG is 3/4" longer than a AR15 BCG so it requires more travel in AR buffer tubes
To be more specific... and in a 308 sized AR ( LFAR .. Large Frame AR )
NOTE the various parts do not interchange.
Typical AR15 carbine buffer.... 2.5" buffer length, 308 carbine spring ( DPMS carbine Pattern )
A5 / Armalite length buffer tube ( 3/4" longer than a AR15 carbine buffer tube ) .... 3.25" buffer.... and you can use a variety of 308 rifle length recoil spring ( Armalite carbine pattern
AR15 rifle length buffer tube... 308 rifle buffer, about 5.2"-5.3" long ( shorter than a AR15 rifle length buffer ) .... 308 rifle recoil spring.
This link shows the differences between the to dominant carbine patterns...
https://www.ar15.com/forums/industry/PSA-when-did-you-guys-switch-the-buffer-system-length-on-the-PA10-/301-286585/