For an AR-10 chambered in .308/7.62 with a collapsible stock, if it has an AR-15 carbine buffer tube (which is 7” long on the inside) then it needs a 2.5” buffer and we recommend the KynSHOT AR10 2.5” carbine hydraulic buffer “Shorty” (Part# RB5004) and an AR-10 carbine buffer spring, either the JP 308 carbine buffer spring (part# JPS-OSC-308) or the SPRINCO AR-10 carbine buffer spring (color code ORANGE - Part# SPRINCO-25762). If your rifle came with a 2.5" buffer and you have not changed your buffer tube, then this is what you need. This same set up works for other calibers in an AR10, large framed AR such as 6.5 Creedmoor and others.
https://www.blitzkriegcomponents.com/hydraulic-kynshot-recoil-buffer-308-carbine-25.html