An effective way to knock it out is with a canon, prefered on the platform saddle of a paracer. Build a trap (a row of foundations and pillars) and let it agro you. Let him glitch against the pillars as a teammate is ready to fire the canon.
For some reason, after the latest update, X-rock elementals (haven't checked other variants) are no longer tameable. Whenever you knock them out, they don't eat and don't have a taming bar. Forcetame also doesn't affect them, so I believe it's a glitch
To tame these turret soakers I’d recommend getting four metal gates 5 pillars 3 ceilings and 3 walls. For the trap and the pillars are supposed to prevent the golems rocks from hitting the cannon. AIM FOR THE HEAD