If so, then how come AR and M14/M1A clones work reliably and HK clones don't. It is because they have to be built to much higher tolerances and are more difficult to make. Period. Fluting a barrel properly is very difficult. I have had experienced machinist/gunsmith friends try it with poor results. The PTR91 is no HK91/G3. Don't believe me, go to the clone section of HKPro.com and it is full of people with PTR problems. The G3 is one of the most controllable full auto 7.62 guns available. I've put thousands of rounds on target. Try that with a M14. There is a big difference between actual recoil and perceived recoil. Anyone who thinks that a bolt action gun has less recoil than any autoloader of the same caliber is ignoring the laws of physics. A HK91/G3 recoil can also be reduced by installing a MSG90 or HK21 buffer. Tell that to my black and blue shoulder after spending an afternoon firing 9MM sub-guns. Exactly. I have fired the UMP in 45 and 9MM and they suck. HK wanted to discontinue the MP5 but could not because nobody wanted the UMP. They are truly horrid. The key word here is FELT recoil as opposed to a weapons ability to stay on target. Facts speak for themselves. Do you really expect anybody to believe all these forces buy weapons based on marketing and inertia, not merit? Albania: Albanian Special forces RENEA and the Albanian Police, further procurement for regular armed forces planned. Algeria: Algerian Airborne Commando Division. Argentina: Used by GEOF, Hawk Special Operations Brigade and Argentine Naval Prefecture Australia: Australian Army—2nd Commando Regiment, Special Air Service Regiment, Royal Australian Air Force No. 1 & No. 2 Airfield Defense Squadrons and various Australian Federal and State law enforcement units. Austria: Used by the EKO Cobra anti-terrorist Azerbaijan: Azerbaijan Interior Guard. Bahrain Bangladesh: Army, Special Forces, Rapid Action Battalion. Bulgaria Bulgaria special forces Belgium: Gespecialiseerde Verkenningsploegen (GVP) / Equipes Specialisees de Reconnaissance (ESR), Speciaal Interventie-Eskadron (SIE) / Escadron Special d'Intervention (ESI). Brazil: Brazilian Army special forces and several, state police departments and Military Police (BOPE, Polícia Militar do Estado de São Paulo, Polícia Militar do Estado do Rio de Janeiro) Cameroon Canada: Various police tactical units, RCMP ERTs, Joint Task Force Two (JTF-2), naval boarding parties, Emergency Task Force (ETF Toronto). Ottawa Police Service Tactical Unit. Chile: 1st Battalion Airborne Forces. Unidad Anti-Terroristas (UAT). Colombia: Lanceros, Agrupación de Fuerzas Especiales Antiterroristas Urbanas (AFEUR). Democratic Republic of the Congo Croatia:for the military and police and special police Cyprus: Police. Czech Republic Denmark: Danish police and special forces. Egypt El Salvador: Used by SWAT Finland: Used by the Finnish police, Finnish Border Guard and Finnish Defence Forces. Designated 9.00 KP 2000 (9.00 konepistooli 2000). France: Used by the Groupe d'Intervention de la Gendarmerie Nationale, French Foreign Legion, Commandement des Operations Speciales (COS), Groupement Special Autonome and certain specialized units within the French Army (MP5A5 and MP5SD3 variants). Georgia:for the police and special police Germany: German State Police, German Federal Police, KSK, Kampfschwimmer, Long Range Reconnaissance Company, Feldjäger (military police), GSG 9. The German Army and German Navy also employ the MP5K. Ghana Greece: Police and Greek Special Forces Directorate. Weapons are manufactured locally by Hellenic Defence Systems (EAS: Ellinika Amyntika Systimata). Honduras Hong Kong: Special Duties Unit, Police Tactical Unit, Airport Security Unit, VIP Protection Unit. Hungary: Used by the Hungarian Police, Hungarian Prison Service and Hungarian Ground Forces. Iceland: Icelandic Coast Guard, Icelandic Crisis Response Unit and Special Forces of the National Commissioner. India: Indian Army special forces, National Security Guards, MARCOS and other units. Indonesia: Indonesian National Armed Forces counter-terrorism unit. Iran: Islamic Republic of Iran Army, Iranian police, Takavar. Weapons are manufactured locally by Defense Industries Organization. Ireland: Sciathan Fianoglach an Airm (Irish Army Rangers). Italy: All Italian special forces. Mostly encountered within GIS, NOCS and COMSUBIN. Recently, some Police units like the Cacciatori di Sardegna (a unit within the Carabinieri specialized in chasing and apprehending fugitives in wildlife environments like mountains or forests), and the Polizia di Stato Airport Security detachment of the Leonardo da Vinci-Fiumicino Airport (Rome) have replaced the standard Beretta M12 with MP5-A5 submachineguns equipped with EOTech holographic sights. Jamaica: Jamaica Constabulary Force (JCF). Japan: Japanese Special Operations Group and Special Assault Team Jordan: SOU-17. Kenya: Kenya Police. Kuwait: Kuwait Army. Latvia: Speciālo Uzdevumu Vienība , OMEGA (special forces) and military police. Lebanon: Navy SEALs Regiment Lithuania: Special forces group "SOJ", Police fast reaction team ARAS, police units Luxembourg Macao: Unidade Táctica de Intervenção da Polícia , Grupo de Operações Especiais , Grupo de Protecção de Altas Entidades e Instalações Importantes. Macedonia: Macedonian Special Forces. Malaysia: Malaysian Armed Forces, various special forces units and law enforcement agencies. Malta Mauritius Mexico: The Mexican Army - GAFE and Infantry Officers, law enforcement agencies such as state, federal and military police. Licence produced by SEDENA. Montenegro: Vojska Crne Gore (VCG). Morocco: Royal Moroccan Armed Forces, G.S.I.G.R., National Police Force, Gendarmerie Royale. Netherlands: Netherlands Marine Corps, Royal Marechaussee military police, DSI counter-terrorism unit and several other police formations. New Zealand: 1st Special Air Service Squadron. Niger Nigeria Norway: Norwegian Defence Force (The MP7 is set to replace the MP5), Beredskapstroppen and Norwegian Police. Pakistan: Pakistan Army standard weapon for close range engagements, built by Pakistan Ordnance Factories under license from HK. Spanish Navy special forces (UOE) operators armed with MP5s. A USMC Military Police Special Reaction Team using the MP5N. Panama GAP Grupo de Acción Policial (Group of Police Action) . Policía Nacional (National police) y Servicio de Protección Institucional SPI (Service of Institutional Protection) Peru Philippines: Armed Forces of the Philippines, and Philippine National Police Special Action Force and other police and SWAT units. Poland: GROM, police special units. Portugal: Various military units, including the Portuguese Army Special Operations and the Portuguese Marine Corps Special Actions Detachment (DAE). Also used by law enforcement agencies Polícia de Segurança Pública, including the Special Operations Group (GOE), and the Portuguese National Republican Guard (GNR), Policia do Exército (PE). Qatar Romania: SRI (Serviciul Român de Informaţii) counter-terrorism unit and certain police units. Russia Saudi Arabia: Special Forces Brigade. Serbia: SAJ, UBPOK, Serbian Military Police and several other police and military formations. Singapore: Singapore Armed Forces Commandos, Singapore Police Force. Slovakia: Slovak police and special forces. Slovenia: Police and special forces. South Africa: Various services. South Korea: ROKA 707th Special Missions Battalion, ROKN Naval Special Warfare Brigade (UDT/SEAL), KNP Special Weapons Attack Team (SWAT), ROKCG Sea Special Assault Team (SSAT). Spain: Various units, including the UOE and the Tercio de Extranjeros y de Moreria. Also GOE (Grupo de Operaciones Especiales), GOES (Grupo Operativo Especial de Seguridad), GEO (Grupo Especial de Operaciones), GEI (Grup Especial d'Intervenció (from Catalonia) and SVA (Customs Service). Sri Lanka: Sri Lanka Army Commando Regiment, Special Task Force. Sudan: Manufactured under a license agreement by Military Industry Corporation as the Tihraga. Switzerland: FSK-17, Army Reconnaissance Detachment and several Swiss police departments (including SWAT- Teams) Sweden: National Taskforce (NI), and Piketen, Swedish Police. Taiwan: Republic of China Army and Republic of China Military Police, Republic of China Marine Corps Frogmen, Republic of China Coast Guard and various Police SWAT and special forces. Thailand: Used by the Royal Thai Police. Turkey: Various services. Built under license from HK by MKEK. United Arab Emirates: UAE Special Forces, Abu Dhabi Police SWAT, Dubai Police SWAT, UAE VIP Protection Team. United Kingdom: UKSF, Metropolitan Police Specialist Firearms Command, Firearms units of police forces, Royal Ulster Constabulary, Police Service of Northern Ireland, Special Air Service. United States: The MP5N is not standardized but in limited use with some special operations forces. Also used by many law enforcement departments and federal agencies. Uruguay Venezuela Vietnam: Battalion special police. British Virgin Islands: Maritime Patrol officers as well as armored car guards use the MP5K. My knowledge on this subject comes from firing tens of thousands of rounds through hundreds of different machine guns. The fact is roller locked weapons are as good if not better than almost anything out there. However they are expensive and difficult to produce properly. So, gun manufactures have stayed or moved away from the design for financial not technical reasons. The G36 and the HK416 are much less expensive than roller lock designs and work well.