The neatest answer for those using the Javelin, Kapita and Sentinel (not compatible with the Spartan 300).

This adapter is designed to be bonded into wooden and synthetic stocks providing the ultimate synergy between the Spartan system and Rifle.

Requires your stock to be machined to take the adapter.

◦Made from 7075 grade alloy.
◦Lightest weight option for all those serious mountain hunters.
◦Represents our most discreet option.
◦Designed to take the Javelin, Kapita and Sentinel.

Classic Gunsmith Adaptor