SYNCHRONIZED SPLIT-BOLT BREECH CLOSURE FOR FIREARMS
US20260146813A1
2026-05-28
19/338,432
2025-09-24
Smart Summary: A new breech closure mechanism improves the operation of firearms using high-pressure cartridges. It features a split-bolt assembly with two parts: a front half that handles loading and firing, and a back half that works with a spring. When a cartridge is fired, the front bolt moves backward while the back bolt moves forward, helping to keep the breech closed for a moment as the bullet exits the barrel. This design enhances the performance of automatic firearms compared to older systems, which often used simpler mechanisms. Overall, it offers a more efficient way to manage the forces during firing without adding complicated parts. 🚀 TL;DR
Abstract:
A synchronized split-bolt breech closure mechanism improves blowback operation for higher pressure cartridges. The mechanism includes a split-bolt assembly with a front bolt half for feeding, chambering, and triggering a cartridge, and back bolt half connected by a variable separation spring separation distance, initiating from an open bolt configuration, where upon cartridge ignition the rearward recoil force on the front bolt half is synchronized with the forward momentum of the back bolt half driven by the main action spring, closing the separation distance which momentum transfer maintains breech closure over a brief interval for the bullet to exit the barrel. The mechanism provides a basis for automatic blowback firearms with enhanced performance over prior art systems, such as the one-piece bolt low pressure blowback of the Thompson M1A1 45 ACP rechambered for the intermediate pressure 50 caliber Action Express, without complex transverse friction or gas-operated closed rotating bolt breech mechanisms.
Applicant:
Interested in similar patents?
Get notified when new applications in this technology area are published.
Classification:
F41A3/74 » CPC main
Breech mechanisms, e.g. locks; Mounting of breech-blocks; Accessories for breech-blocks or breech-block mountings Obturating or packing devices for gas leak prevention in breech mechanisms
F41A3/22 » CPC further
Breech mechanisms, e.g. locks; Bolt action, i.e. the main breech opening movement being parallel to the barrel axis; Rigid bolt locks, i.e. having locking elements rigidly mounted on the bolt or bolt handle and on the barrel or breech-housing respectively the locking elements effecting a rotary movement about the barrel axis, e.g. rotating cylinder bolt locks hand-operated the locking being effected by rotating the operating handle or lever transversely to the barrel axis
Description
BACKGROUND OF THE INVENTION
The invention is a new type of firearm automatic breech closure firing device synchronization control of a blow-back initiated mechanism.
During the World War II era the US War Department explained the fundamentals of small arms bolt action, semiautomatic, and automatic operation. U.S. Pat. No. 1,131,319 Breech Closure For Firearms by Commander John Blish introduced the bimetallic friction-delayed blowback Blish Lock mechanism; which was then engineered by General John T. Thompson founder of the Auto-Ordinance Company to manufacture the 1921 Thompson submachine gun chambered for the low pressure 45 ACP cartridge.
The Blish Lock bimetallic friction-delayed blowback mechanism complexity was reduced somewhat with the 1928 Thompson.
Current firearm high pressure breech closure mechanisms are generally gas-operated closed rotating bolt breech complex mechanisms.
The 1942 Thompson M1A1 manufactured by Auto-Ordinance and Savage Arms features the most simplified automatic blowback operation, shown in FIG. 1, which upon triggering from an open bolt releases the bolt to slide forward by means of an action spring and chamber a round. Upon seating the round the bolt chambering surface presses against the the rear of the chambered cartridge, whereupon the fixed firing pin fires the primer providing breech closure inertia long enough for the explosive ballistic pressure to propel the bullet out of the barrel before significantly overcoming the bolt and action spring inertia blowing the bolt back to recycle another round.
Thus the prior art of simplified blowback operation has been limited to lower powered cartridges, such as the 45 ACP, due to the heavier bolt and greater action spring tension inertia required for breech closure of higher powered cartridges.
SUMMARY OF THE INVENTION
The invention synchronized split-bolt momentum breech closure mechanism, shown in FIG. 2, facilitates a higher pressure cartridge blowback operation by means of the front half of the split-bolt performing the feeding, chambering, and triggering of the cartridge; which resulting explosion reward recoil pressure on the bolt chambering surface is synchronized with the forward momentum of the back half of the split-bolt driven by the main action spring. The front and back halves of the split-bolt are connected by a separation action spring, so that when fired from an open bolt as the front half of the split-bolt makes contact and triggers the round the back half of the split-bolt is still traveling forward closing the separation distance compressing the separation action spring transferring its forward momentum driven by the main action spring until impact synchronized with rearward traveling recoil momentum.
Thus by means of a variable separation action spring tension and distance, the synchronization of momentum between the chamber explosion rearward recoil force on the bolt chambering surface with the forward momentum of the back half of the split-bolt from the main action spring can be adjusted or tuned to create breech closure time enough for the bullet to leave the muzzle of the barrel before significantly driving the entire split-bolt assembly back to recycle another round.
The invention synchronized split-bolt momentum breech closure mechanism therefore creates the platform for semiautomatic and automatic blowback mechanisms to support higher pressure cartridges without the prior art more complicated transverse friction-delayed sliding breech lock and gas-operated rotating breech lock mechanisms.
For example, the one-piece bolt blowback operation of the M1A1 45 ACP caliber could be rechambered by means of the invention synchronized split-bolt momentum breech closure mechanism to fire the intermediate pressure 50 caliber Action Express cartridge.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the prior art simplified automatic blowback one-piece bolt 1, fixed firing pin 2, cartridge chambering surface 3, action spring 4, cartridge recoil force 5, and action spring force 6.
FIG. 2 shows the invention split-bolt front half 1, back half 2, firing pin 3, bolt chambering surface 4, hammer and pin 5, frame contact surface 6, split bolt separation action spring 7, split-bolt separation spring clip 8, main action spring 9, split-bolt separation distance 10, recoil force 11, and combined separation and main action spring force 12.
DETAILED DESCRIPTION OF THE INVENTION
The invention synchronized split-bolt breech closure operation initiates from the open bolt configuration. Triggering the split-bolt front half 1 and back half 2 forward motion driven by the main action spring 9 results in the configuration of FIG. 2 wherein the lower triangular lobe of the hammer and pin 5 has made contact with frame surface 6 and rotated the hammer about its pin striking the firing rod 3, igniting the primer and main charge exponential rise to peak ballistic pressure over typically five ten thousands of a second, as described in U.S. Pat. No. 1,131,319, generating recoil force 11 acting on the cartridge chambering surface area of the bolt 4. The rearward recoil momentum is met by the forward momentum of the split-bolt back half, which closes separation distance 10 set by split-bolt separation spring clips 8 attaching the separation spring 7 and main action spring 9 to the back half of the bolt. The impact of the trailing back half of the split-blot with the front half generates synchronized momentum breech closure until the bullet leaves the muzzle of the barrel.
Synchronization of colliding rearward recoil momentum and forward split-bolt momentum converts significant total momentum energy into transverse mechanical energy and heat.
Synchronization timing is tunable by means of the several variables of the split-bolt separation distance, separation spring compressive tension and length, main action spring compressive tension and length, and total weight ratio of split-bolt front and back halves.
Thus the invention synchronized split-bolt breech closure mechanism introduces a firearms engineering capability for intermediate pressure cartridges in greatly simplified blowback operation form over the prior art friction-delayed and gas-operated closed rotating bolt breech mechanisms. For example, the invention upgrades the one-piece bolt blowback operation of the M1A1 45 ACP caliber to facilitate a synchronized split-bolt momentum breech closure for the intermediate pressure 50 caliber Action Express cartridge.
Claims
1. A synchronized split-bolt breech closure mechanism for a firearm, comprising: a. a split-bolt assembly having a front bolt half and a back bolt half, the front bolt half configured to feed, chamber, and trigger a cartridge, and the back bolt half connected to the front bolt half by a variable action separation spring; b. a split-bolt separation spring clip configured to maintain a separation distance between the front bolt half and the back bolt half; c. a firing pin and hammer assembly operatively coupled to the front bolt half, wherein the hammer contacts a frame surface to rotate and strike the firing pin, initiating cartridge ignition; d. wherein a rearward recoil force from the cartridge explosion acts on a chambering surface of the front bolt half, synchronized with a forward momentum of the back bolt half closing the separation distance, thereby generating a momentum breech closure sufficient for a bullet to exit a barrel before the split-bolt assembly recoils to cycle a subsequent cartridge.
2. The mechanism of claim 1, wherein the split-bolt assembly is configured to operate in an open bolt configuration, initiating breech closure upon releasing the trigger mechanism.
3. The mechanism of claim 1, wherein the front bolt half includes a cartridge chambering surface and fixed firing pin; which front bolt half is separated from the back bolt half by a separation action spring, the forward momentum of which by means of a main action spring is synchronized with the rearward recoil momentum such that the impacting surfaces operation maintains breech closure during the brief interval of cartridge ignition and buildup of ballistic pressure through bullet exit.
4. The mechanism of claim 1, wherein the variable main action spring and split-bolt separation spring tensions and lengths are fixed to the split-bolt front and back halves by means of clips, with individual weights of the split-bolt halves and their weight ratio calibrated to synchronize the forward impact of the back bolt half with the rearward recoil force on the front bolt half, facilitating support for intermediate pressure cartridges.
5. The mechanism of claim 1, wherein the synchronized split-bolt breech closure mechanism is adapted to replace a one-piece bolt blowback system originally applied to relatively low pressure 45 ACP cartridges, enabling a firearm to fire a higher-pressure cartridge; such as the intermediate pressure 50 caliber Action Express, without requiring relatively complex transverse friction-delayed or gas-operated closed rotating bolt breech locking mechanisms.
6. The mechanism of claim 1, wherein the split-bolt assembly is configured to operate by means of the prior art closed bolt breech closure mechanisms, such as U.S. Pat. No. 7,562,614.
Images & Drawings included:
Sources:
- United States Patent and Trademark Office - verify current appl. status at the USPTO↗
Recent applications in this class:
- » 20130014634 2013-01-17
Sealing ring and propellant charge cartridge - » 20070028756 2007-02-08
Seal, in particular for caseless ammunition