The Troy M14 MCS will work with all Springfield M1A rifles except ones that feature a rear lugged receiver. The Troy M14 BattleRail however will work with all models including ones that feature a rear lugged receiver.
Troy uses the standard AR-15 barrel thread pitch 1/2×28 TPI for all 5.56 muzzle brakes and flash hiders. Troy also uses 5/8×24 TPI for all 6.8 and 7.62 calibers.
Any QARS rail sections.
No, currently Troy does not produce a .308 handguard that is compatible with the RRA .308 platform. RRA uses a different thread pitch and length on their receivers that greatly differs from the Armalite and DPMS rifle systems.
Yes, Troy BUIS will co-witness with many models of Eo-Tech optical sights such as:
Troy BUIS will also co-witness in the lower third of the optic with these models: