# US 5,710,389 A · Breech bolt and lock assembly

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- Number: US 5,710,389 A
- Document ID: US5710389A
- Status: Granted
- Kind: A
- Application number: 08/514,884
- Filed: 1995-08-14
- Granted: 1998-01-20
- Earliest claimed: 1995-08-14
- Assignees: The United States of America as represented by the Secretary of the Navy
- Inventors: Michael Canaday
- Web page: https://patentgrep.com/patent/US5710389A

## CPC

- F41A 3/54: Bolt locks of the unlocked type, i.e. being inertia operated
- F41A 3/82: Coil spring buffers (F41A3/80 takes precedence)
- F41A 19/13: Percussion or firing pins, i.e. fixed or slidably-mounted striker elements; Mountings therefor {(F41A19/26 takes precedence)}
- F41A: FUNCTIONAL FEATURES OR DETAILS COMMON TO BOTH SMALLARMS AND ORDNANCE, e.g. CANNONS; MOUNTINGS FOR SMALLARMS OR ORDNANCE

## Abstract

A breech bolt and lock assembly for a gas-operated firearm is provided. The ssembly is contained within a bolt housing which in turn contains a bolt operating spring and a two-part bolt mechanism. The two-part bolt has a cylindrical outer bolt which encloses the inner bolt and firing pin. A second spring operates the firing pin. During firing, the inertia of the firing pin and inner bolt prevents the sudden rearward movement of the discharging cartridge. There is no other locking of the breech, however, the weight of the inner bolt and pin assembly may be changed to accommodate different propellant loads.

## Claims

### Claim 1

A breech bolt and lock assembly for a gas-operated firearm comprising:
a bolt housing having a cylindrical shape;
a first spring contained within said bolt housing;
a two-part bolt assembly having an outer cylindrical bolt slideably positioned within said bolt housing and operated by said first spring and having an inner bolt and weighted pin mechanism slideably positioned within said outer cylindrical bolt and providing an inertial bolt lock; and
a second spring positioned within said outer cylindrical bolt and enclosing said inner bolt and weighted pin mechanism and further urging said inner bolt and pin assembly toward the firing position.

### Claim 2 (depends on 1)

A breech bolt assembly for a gas-operated firearm as in claim 1 wherein said inner bolt and firing pin mechanism comprises a weighted cylindrical firing pin having a pointed center for engaging a cartridge.

### Claim 3

A breech bolt and lock assembly for a gas-operated firearm comprising:
a housing;
an outer bolt contained within said housing;
a bolt-operating spring positioned within said housing and engaging said bolt; and
a weighted firing pin attached to an inner bolt adapted for use with both dual spotter cartridges and reduced propellant single spotter cartridges interchangeably.

### Claim 4 (depends on 3)

A breech bolt and lock assembly for a gas-operated firearm as in claim 3 wherein said weighted firing pin has a pointed center for igniting a cartridge primer.