Should work fine with the game's spetznaz model, I have a working one of my own with pistols. All I did was rename a copy of the original model so I could reskin it, but I didn't change anything other than a few path names in the model and I saw the beretta proxy in there. Here is a cut&paste of one of my working ones with the original model:
class CfgPatches
{
   class DAC_ops
   {
      units[] = {DAC_op1};
      weapons[] = {};
      requiredVersion = 1.85;
   };
};
class CfgModels
{
   class Default
   {
      sections[]={};
      sectionsInherit="";
   };
   class Man: Default
   {
      sections[] =
      {
         "head injury","body injury",
         "l arm injury","r arm injury","p arm injury",
         "l leg injury","r leg injury","p leg injury",
         "medic",
         "hlava",
         "krk",
         "zasleh"
      };
      sectionsInherit=Head;
   };
   class DAC_op1: Man{};
};
class CfgVehicles
{
   class All{};
   class AllVehicles:All{};
   class Land: AllVehicles{};
   class Man: Land{};
   class Soldier: Man{};
   class SoldierEB: Soldier{};
   class SoldierESaboteur: SoldierEB{};
   class DAC_op1: SoldierESaboteur
   {
      scope=2;
      vehicleClass="DAC SF";
      displayName="Spetznaz (G36a)";
      weaponSlots="1 + 16 + 2*4096 + 10*256 + 2 + 4*32";
      weapons[]={"G36a","GlockS","Throw","Put"};
      magazines[]={"G36aMag","G36aMag","G36aMag","G36aMag","G36aMag","G36aMag","GlockSMag","GlockSMag","GlockSMag","GlockSMag"};
   };
};