. 1

TO ACQUAINT CLASS WITH BASIC SYSTEMS OF OPERATION.

PREVIEWPART I - GAS SYSTEM OF OPERATION.

PART II - BLOWBACK SYSTEM OF OPERATION.

PART III - RECOIL SYSTEM OF OPERATION.

GAS SYSTEM OF OPERATION

GAS SYSTEM OF OPERATION

FORCE DERIVED FROM PROPELLANT GASES.

40 % OF THE ENERGY CONTAINED WITHIN THE PROPELLANT IS EJECTED AT THE MUZZLE.

GAS TAPPED FROM THE BARREL TO OPERATE THE PISTON AND TO COMPLETE CYCLE OF OPS.

MAIN COMPONENTS

LOCATION OF GAS VENTIDEAL LOCATION:NO EFFECT ON BALLISTICS.AFTER ABP.

LOCATION OF GAS VENT: NEARCHAMBER VS NEAR MUZZLE

FOULING (UNBURNT PARTICLES).

AFFECT MUZZLE VELOCITY.

WEAPON NOT MECHANICALLY SAFE.

POOR ACCURACY.HIGH RATE OF FIRE.ROBUST PARTS.

FOULING (RESUBLIMATION).

MINIMUM AFFECT ON BALLISTICS.

WEAPON MECHANICALLY SAFE.

ACCURATE FIRE.SLOW RATE OF FIRE.LARGE GAS VENT.INCREASE IN LENGTH

OF CYLINDER & PISTON.

MECHANICAL SAFETYACHIEVED BY LOCKING & UNLOCKING.IN 7.62MM LMG/SLR THE GAS VENT IS

MADE AT 12" FROM THE MUZZLE END.GASES TAPPED AT THIS POINT ARE

1/3RD OF THE PEAK PRESSURE - 07 TSI (965 BAR).

CONTROL OF THE OPERATING ENERGY

DESIRABLE TO CONTROL AND VARY THE AMOUNT OF ENERGY AS PER OCCASION.

VARIOUS MEANS VARIABLE SIZE GAS TRACK.CONTROL VARYING THE AMOUNT OF GAS EXHAUSTED TO ATMOSPHERE.

CONSTANT VOLUME VALVE.VARIABLE EXPANSION VOLUME AT THE HEAD OF PISTON.

VARIATION IN RATE OF FIRE.

VARIABLE SIZE GAS TRACK

VARIABLE EXHAUST

CONSTANT VOLUME SYSTEM

CONSTANT VOLUME SYSTEM

VARIABLE EXPANSION VOLUME

CONTROL OF CYCLIC RATE OF FIRE

TYPES OF GAS OPERATION

SHORT STROKE VS LONG STROKE

GENERALLY DOES NOT MOVE MORE THAN 3”.

DOES A TAPPING ACTION & IMPARTS MOMENTUM TO MOVING PARTS.

EXAMPLE 7.62MM SLR (FN FAL), 7.62MM DRAGUNOV SNIPER RIFLE.

MOVES MORE THAN 3”.

MOVES THE ENTIRE DISTANCE WITH MOVING PARTS.

EXAMPLE 5.56MM INSAS FAMILY, 7.62MM LMG (BREN).

DIRECT GAS ACTION

NO PISTON.GAS PUSHES THE BREECH BLOCK.ALSO CALLED ‘DIRECT IMPINGEMENT’.LIGHT WEIGHT WEAPON & SIMPLE DESIGN.MORE FOULING.EXAMPLE 5.56MM AR-15/M-16 RIFLE..

ADVANTAGES - GAS OPERATIONFLEXIBILITY IN THE RATE OF FIRE.LIGHT WEIGHT.ACCURACY.RATE OF FIRE.

DISADVANTAGES - GAS OPERATION

FUMES.EROSION.CARBON DEPOSITS.BARREL CHANGE DIFFICULT.

BLOWBACK SYSTEM OF OPERATION

BLOWBACK SYSTEM OF OPERATION

THE ENERGY IS SUPPLIED DIRECTLY TO THE BOLT BY THE BACKWARD MOVEMENT OF THE CARTRIDGE CASE, CAUSED BY GAS PRESSURE.

CARTRIDGE CASE ACTS LIKE THE PISTON.ALSO KNOWN AS ‘SPENT CASE EJECTION’

SYSTEM OF OPERATION.

MAIN COMPONENTS

BASIC REQUIREMENTSCASE MUST BE FREE TO MOVE IN CHAMBER.

TAKE UP EXCESS CARTRIDGE HEAD SPACE. PROVIDE THE FORCE AGAINST THE BREECH

BLOCK.CASE MUST BE RESTRAINED IN THE

CHAMBER.WHEN PRESSURE IS HIGH.

MUTUALLY CONTRADICTORY.BASIS FOR DIFF TYPES OF BLOW BACK

SYSTEM.

TYPES OF BLOWBACK SYSTEMSIMPLE BLOWBACK.DELAYED BLOWBACK.BLOWBACK WITH LOCKED BREECH.BLOWBACK WITH API.

SIMPLE BLOW BACKBLOW BACK PROVIDES ALL THE

OPERATING ENERGYMOVENMENT OF CARTRIDGE CASE IS

RESTRAINED.CONTROLLED BY MASS, INERTIA OF

BREECH BLOCK AND STRENGTH OF RETURN SPRING.

.

CHARACTERISTICS OF SIMPLE BLOW BACK WEAPONS

UNLOCKED BREECH.HEAVY INERTIA TYPE BREECH BLOCK.SIMPLICITY.STRONG RETURNING SPRING.USUALLY A PARALLEL SIDED CART CASE.LIMITED ACCURACY IN HAND HELD

AUTOMATIC FIRE.

DELAYED BLOWBACKCERTAIN AMOUNT OF MECHANICAL

DELAY IS CREATED TO ALLOW PRESSURE TO DROP TO A SAFE LEVEL.

THUS A FORM OF RESISTANCE IS GIVEN TO THE BLOWBACK FORCES INITIALLY.

TWO MAJOR TYPES:ROLLER DELAYED BLOWBACK.LEVER DELAYED BLOWBACK.

ROLLER DELAYED BLOWBACK

LEVER DELAYED BLOWBACK

BLOW BACK WITH LOCKED BREECH

BREECH BLOCK IS LOCKED TILL SAFE PRESSURE IS ACHIEVED.

FORCE REQD TO UNLOCK THE BREECH BLOCK PRODUCED FROM GAS PRESSURE OR RECOIL OF BARREL.

ENERGY REQD TO OPERATE THE CYCLE GIVEN TO THE BOLT.

BLOWBACK WITH APIRD IS FIRED WHILE IT IS STILL BEING

CHAMBERED AND BEFORE THE BOLT REACHES THE LIMIT OF ITS FORWARD TRAVEL.

ENERGY PRODUCED HAS NOW TWO FUNCTIONS.TO SLOW AND STOP THE FORWARD MOVING

BOLT.TO PROPEL THE BOLT TO THE REAR.

MASS OF THE BOLT CAN BE REDUCED TO HALF.

DANGERS IN API SYSTEMSEARLY FIRING.LATE FIRING DUE TO HANG FIRE.MECHANICAL OBSTRUCTION IN THE

CHAMBER.HAND CHAMBERING.OVERSIZED RD.

SAFETY DEVICES IN API SYSTEMS

POSITIVE FIRING.HOODED CHAMBER.A DOUBLE LOADING STOP.A HOLDING OPENING DEVICE.

CHARACTERISTICS OF BLOW BACK WITH API

BREECH BLOCK STILL MOVING FORWARD WHEN THE PRIMER IS FIRED.

UNLOCKED BREECH.HEAVY BREECH BLOCK.POWERFULL RETURNING SPRINGS.SPECIAL SAFETY DEVICES.PARALLEL SIDED CART CASE.SUSCEPTIBILTY TO VARIATION IN

AMMUNITION.

MECHANICAL SAFETY IN BLOWBACK

HEAVY BREECH BLOCK.REAR 1/8TH INCH OF CARTRIDGE CASE

MADE STRONG.STRONG RETURN SPRING.LOW POWER AMMUNITION.PARALLEL CHAMBER & PARALLEL

AMMUNITION.SHORT BARREL.BLOWBACK WITH API.

ADVANTAGES - BLOWBACK OPERATION

SIMPLE DESIGN.CHEAP.ROBUST.

DISADVANTAGES - BLOWBACK OPERATION

HEAVY BREECH BLOCK.INACCURATE.SHORT EFFECTIVE RANGE.NO MEANS OF ADJUSTING POWER.FUMES.PRECISION AMMUNITION.REDUCED MUZZLE VELOCITY.

COMPARISON

RECOIL SYSTEM OF OPERATION

RECOIL SYSTEM OF OPERATIONNEWTON’S THIRD LAW.FORWARD MOVEMENT OF BULLET INSIDE

THE BARREL EXERTS AN EQUAL & OPPOSITE FORCE TO THE BREECH BLOCK & BARREL.

THE WEAPON IS PUSHED BACK - RECOIL.MECHANICAL SAFETY: BOLT LOCKED

WITH BARREL.

MAIN COMPONENTS

CHARACTERISTICS - RECOIL OPERATION

FREE FLOATING BARREL WITH SPRING.BOLT LOCKED WITH BARREL.BARREL UNLOCKING MECH.LOCKING/UNLOCKING DEVICE FOR BOLT.

TYPES OF RECOIL OPERATIONLONG RECOIL

BARREL & BOLT MOVE THE ENTIRE LENGTH TOGETHER.

SHORT RECOILBARREL & BOLT DO NOT MOVE THE ENTIRE LENGTH TOGETHER.

CYCLE OF OPERATIONS – LONG RECOIL

1. READY TO FIRE POSITION. BOLT IS LOCKED TO BARREL, BOTH ARE FULLY FORWARD.

2. RECOIL OF FIRING FORCES BOLT AND BARREL FULLY TO THE REAR, COMPRESSING THE RETURN SPRINGS FOR BOTH.

3. BOLT IS HELD TO REAR, WHILE BARREL UNLOCKS AND RETURNS TO BATTERY UNDER SPRING FORCE. FIRED ROUND IS EJECTED.

4. BOLT RETURNS UNDER SPRING FORCE, LOADS NEW ROUND. BARREL LOCKS IN PLACE AS IT RETURNS TO BATTERY.

CHARACTERISTICS - LONG RECOIL

BARREL & BREECH BLOCK LOCKED.BARREL & BREECH BLOCK TRAVEL ENTIRE

LENGTH TOGETHER.EXTRACTION & EJECTION IN FORWARD

MOVEMENT.SLOW RATE OF FIRE.NO FUMES IN BODY OF WEAPON.REDUCED STRESS ON WEAPON.INACCURATE.SIGHTING PROBLEMS - BARREL MOVEMENT.QUICK BARREL CHANGE EASY.

CYCLE OF OPERATIONS – SHORT RECOIL

1. READY TO FIRE POSITION. BOLT IS LOCKED TO BARREL, BOTH ARE FULLY FORWARD.

2. UPON FIRING, BOLT AND BARREL RECOIL BACKWARDS A SHORT DISTANCE WHILE LOCKED TOGETHER. NEAR THE END OF THE BARREL TRAVEL, THE BOLT AND BARREL UNLOCK.

3. THE BARREL STOPS, BUT THE UNLOCKED BOLT CONTINUES TO MOVE TO THE REAR, EJECTING THE EMPTY SHELL AND COMPRESSING THE RECOIL SPRING.

4. THE BOLT RETURNS FORWARD UNDER SPRING FORCE, LOADING A NEW ROUND INTO THE BARREL.

5. BOLT LOCKS INTO BARREL, AND FORCES BARREL TO RETURN TO BATTERY.

DESIGN FEATURES -SHORT RECOIL

HIGH RECOIL VELOCITY OF THE BARREL AND BOLT AT THE TIME OF UNLOCKING.

BLOW BACK ASSISTANCE.ACCELERATOR EFFECT.

CHARACTERISTICS - SHORT RECOIL

LOCKED BARREL & BREECH BLOCK.BLOWBACK ASSISTANCE.BARREL & BOLT DO NOT MOVE THE ENTIRE

LENGTH TOGETHER.EXTRACTION & EJECTION IN REAR TRAVEL.ACCELERATOR EFFECT.HIGH RATE OF FIRE.MORE STRESS ON GUN.PARTIAL FUMES COME INTO THE BODY.MORE ACCURATE THAN LONG RECOIL.QUICK BARREL CHANGE EASY.

NEED FOR RECOIL INTENSIFIERFOR SUSTAINED AND HEAVY RATE OF

FIRE.BARREL,BARREL EXTENSION, BOLT HEAD

AND LOCKING DEVICE SUBJECTED TO FORCE RESULTING FROM HIGH PRESSURE.

ADDITIONAL SOURCE TO ACCELERATE THE BARREL AND BOLT.

RECOIL INTENSIFIER OR MUZZLE BOSSTER.

RECOIL INTENSIFIER

FACTORS AFFECTING RECOIL OPERATIONLACK OF ENERGY – 0.1% OF TOTAL ENERGY.WEIGHT DISTRIBUTION.

INITIAL VELOCITY WHEN SEPARATION OCCURS.

BLOW BACK ACTION.ACCELERATOR .DESIGN LIMITATION.

ACCURACY – MOVENMENT OF BARREL.COOLING – CHANGING/ MASSIVE BARREL.BARREL WITHDRAWAL –SUITABLE IN AFVs.FOULING – MINIMAL(RECOIL INTENSIFIER).FUMES.

ADVANTAGES - RECOIL OPERATION

RELIABLE.ROBUST.SIMPLE BARREL CHANGE.NO FOULING.LITTLE FUMES.SUITABLE FOR AFV’S.

DISADVANTAGES - RECOIL OPERATION

HEAVY.SLOW RATE OF FIRE.NO MEANS OF ADJUSTING POWER.COSTLY.LESSER ACCURATE IN HIGHER CALIBRE

WEAPONS.

LONG RECOIL VS SHORT RECOILCHARACTERISTIC

SLONG

RECOIL SHORT RECOIL

• REARWARD TRAVEL

COMPLETE DISTANCE

SHORT DISTANCE

• EXTRACTION/ EJECTION

FORWARD TRAVEL

REARWARD TRAVEL

• FEEDING FORWARD TRAVEL

FORWARD TRAVEL

• RATE OF FIRE 80 RPM MAXIMUM

200 RPM MAXIMUM

• ACCURACY POOR MORE ACCURATE

• FUMES NONE PARTIAL FUMES

COMPARISON OF SYSTEM OF OPERATION

CHARACTERISTIC BLOWBACK RECOIL GAS

• SAFETY UNSAFE SAFE SAFE• WEIGHT HEAVY HEAVY LIGHT

• ACCURACY INACCURATE

INACCURATE

ACCURATE

• RATE OF FIRE LIMITED LIMITED HIGH• COST CHEAP COSTLY COSTLY