ok, i found it out:
#define NumOfWeapons 4
short Weapons[NumOfWeapons] = { 830, 767, 788, 809 }; //Sind die Nummern von Intervention, Barrett, WA2000 und M21.
bool SniperRifleIsEquiped = false;
for(int i = 0; i < ENTITIESMAX; i++)
{
if(localclientnum == mw2_entities[i].clientnum)
{
for(int j = 0; j < NumOfWeapons; j++)
{
for(int k = 0; k < 7; k++)
{
if(mw2_entities[i].WeaponNum == Weapons[j] + k) //Weaponnumber (j) + Attachment(k) = Gesuchte Waffe
{
SniperRifleIsEquiped = true;
}
}
}
}
}