Get a copy of _damage.gsc and replace the start of the Callback_PlayerDamage_internal code with this:
Code:Callback_PlayerDamage_internal( eInflictor, eAttacker, victim, iDamage, iDFlags, sMeansOfDeath, sWeapon, vPoint, vDir, sHitLoc, psOffsetTime ) { if(eAttacker.pers["team"] == game["attackers"] && isSubStr(sWeapon, "model1887") iDamage = 1000; //Damage here