Patent Publication Number: US-2023142958-A1

Title: Charging handle for sub-caliber upper receiver actions

Description:
PRIORITY CLAIM 
     This application claims priority to U.S. Provisional Patent Application Ser. No. 63/227,211, filed on Jul. 29, 2021, the entire contents of which are incorporated herein by reference and relied upon. 
    
    
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application refers to co-pending PCT Patent Application Serial No. PCT/US21/14953, filed Jan. 25, 2021, which claims priority to U.S. Provisional Patent Application Ser. No. 62/965,048, filed on Jan. 23, 2020; and U.S. patent application Ser. No. 17/684,387, filed Mar. 1, 2022, which claims priority to PCT/US21/14953, filed Jan. 25, 2021, which in turn claims priority to U.S. Provisional Patent Application Ser. No. 62/965,048, filed on Jan. 23, 2020, the contents of each of which are incorporated herein in their entireties and relied on. 
     BACKGROUND 
     The AR-15 and M16 firearm platforms are flexible, enabling reliable firing of many calibers of ammunition. However, ammunition native to the AR-15 and M16 platforms (e.g., 0.223 and 5.56 rounds) are relatively expensive, making regular training exercises with the AR-15 and M16 platforms costly. Sub-caliber conversion kits including a sub-caliber bolt and carrier and a sub-caliber ammunition magazine have recently been developed to address some of these economic concerns. For example, PCT Patent Application Serial No. PCT/US21/14953, filed Jan. 25, 2021, discloses a  22 LR ammunition magazine, bolt, and carrier compatible with a wide range of AR-15 and M16 platforms manufactured to cycle larger ammunition rounds. However, standard AR-15 and M16 charging handles tend to suffer from compatibility issues with the sub-caliber bolts and carriers, and can cause spent cartridges to jam in the ejection port of the upper receiver. 
     Others have proposed complicated solutions to these problems, including telescoping charging handles, but such complicated designs also suffer from significant performance and compatibility issues. A need persists for reliable charging handles compatible with sub-caliber (e.g.,  22 LR) actions for AR-15 or M16 upper receivers, such as the Sig Sauer MCX rifle upper receiver. 
     SUMMARY 
     The present disclosure provides charging handles compatible with hold-open bolt carriers for using low-cost (e.g.,  22 LR) ammunition in a standard AR-15 or M16 upper receiver, such as an upper receiver of a Sig Sauer MCX firearm. 
     In some embodiments, the present disclosure provides a charging handle  10  for an upper receiver UR of a firearm, the charging handle comprising: an elongated stem  28 ; a bolt hook  38  disposed at a distal end of the elongated stem; a head  26  disposed at a proximal end of the elongated stem; at least one latch  30   a , 30   b  disposed in a seating aperture  26   a , 26   b  of the head; and a stabilizer  64  disposed on at least a portion of the elongated stem. 
     In other embodiments, the present disclosure provides a charging handle  10  for an upper receiver UR of a Sig Sauer MCX firearm fitted with a sub-caliber bolt carrier group BCG, the charging handle comprising: an elongated stem  28 ; a bolt hook  38  disposed at a distal end of the elongated stem and including a concave portion  38   a  for contacting a portion of the bolt carrier group; a head  26  disposed at a proximal end of the elongated stem and including at least one seating aperture  26   a , 26   b ; at least one latch  30   a , 30   b  disposed in the at least one seating aperture  26   a , 26   b ; and a stabilizer  64  extending from a bottom surface  28   c  of the elongated stem. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows a perspective view of a charging handle consistent with one embodiment of the present disclosure. 
         FIG.  2    shows a side view of the charging handle of  FIG.  1   . 
         FIG.  3    shows a top view of the charging handle of  FIG.  1   . 
         FIG.  4    shows a bottom view of the charging handle of  FIG.  1   . 
         FIG.  5    shows a proximal end view of the charging handle of  FIG.  1   . 
         FIG.  6    shows a distal end view of the charging handle of  FIG.  1   . 
         FIG.  7    shows a representative exploded view of the charging handle of  FIG.  1    aligned with a sub-caliber bolt and bolt carrier compatible with a Sig Sauer MCX rifle. 
         FIG.  8    shows a perspective exploded view of an upper receiver and standard charging handle of a Sig Sauer MCX firearm. 
         FIG.  9    shows a perspective exploded view of a bolt carrier group and recoil system of a Sig Sauer MCX firearm. 
         FIG.  10    shows a perspective exploded view of a lower receiver of a Sig Sauer MCX firearm. 
         FIG.  11    shows a perspective exploded view of a barrel assembly and gas valve assembly of a Sig Sauer MCX firearm. 
         FIG.  12    shows a photograph of a Sig Sauer MCX bolt carrier croup, recoil system, and charging handle. 
         FIG.  13    shows a photograph of a proximal end view of a Sig Sauer MCX barrel/chamber. 
     
    
    
     DETAILED DESCRIPTION 
     Referring generally to  FIGS.  1 - 7   , the present disclosure provides charging handles  10  compatible with hold-open bolt carriers for using low-cost (e.g.,  22 LR) ammunition in a standard AR-15 or M16 upper receiver, such as an upper receiver of a Sig Sauer MCX firearm. The charging handles  10  consistent with the present disclosure generally include an elongated stem  28  including a bolt hook  38  disposed at its distal end, a head  26  disposed at its proximal end, and a stabilizer  64  configured to slidably mate with spring channels SC 1 ,SC 2  of an upper receiver UR, such as a Sig Sauer MCX upper receiver. 
     The elongated stem  28  is generally sized and shaped to fit over and distally forward of a bolt carrier group BCP within an upper receiver UR of a firearm. The bolt B reciprocates forward and backward within the chamber BAC of the upper receiver UR as ammunition rounds (not shown) are cycled through the firearm; the elongated stem  28  is configured to not interfere with the reciprocating action of the bolt B during normal operation. 
     The bolt hook  38  is disposed at the distal end of the elongated stem  28 , and is sized and shaped to contact a portion of the bolt carrier group BCG as the charging handle  10  is withdrawn proximally from the upper receiver UR. The bolt hook  38  has a height h sufficient to contact an upper surface of the bolt carrier group BCG without interfering with the reciprocating action of the bolt B during normal operation. In some embodiments, the height h is about 3 cm to about 10 cm, for example about 3 cm, about 3.5 cm, about 4 cm, about 4.5 cm, about 5 cm, about 5.5 cm, about 6 cm, about 6.5 cm, about 7 cm, about 7.5 cm, about 8 cm, about 8.5 cm, about 9 cm, about 9.5 cm, or about 10 cm. 
     In some embodiments, the bolt hook  38  includes a concave contour  38   a  on its proximal face. When present, the concave contour  38   a  improves purchase of the bolt carrier group BCG with the bolt hook  38 . 
     In some embodiments, the bolt hook  38  does not include a channel. For example and without limitation, conventional charging handles typically include a channel through which a gas tube feeds to provide reciprocating power to the bolt B from the gas vent assembly GVA. Alternatively, conventional charging handles specifically designed for the Sig Sauer MCX rifle system do not typically include a channel for accommodating a gas tube because the Sig Sauer MCX recoil system&#39;s gas vent assembly GVA directs gas to a piston P that forces an op rod OR associated with the bolt carrier group BCG proximal; the op rod OR includes a bolt hook catch BHC located proximal to the intersection of the piston P and the op rod&#39;s piston junction PJ. 
     The head  26  is disposed at the proximal end of the elongated stem  28  and is configured to enable the user to cause release and proximal retraction and removal of the bolt carrier group BCG from the chamber BAC. The head  26  includes a handle-shaped form. The head  26  may include a single latch  30   a  located on one side of the handle-shaped form, or alternatively may include one latch  30   a  on one side of the handle-shaped form and a second latch  30   b  located on the opposite side of the handle-shaped form. activation of the latch  30   a , 30   b  releases the head  26  (e.g., retracts a catch, not shown) to enable the charging handle  10  to be withdrawn rearward from the upper receiver UR. The one or more latches  30   a , 30   b  may be disposed within one or more seating apertures  26   a , 26   b  of the head  26 . 
     The stabilizer  64  is configured to stabilize the charging handle  10  within the upper receiver UR. Generally, the stabilizer  64  is sized and shaped to fit within one or more channels of the upper receiver UR. In some embodiments, the one or more channels are spring channels SC 1 ,SC 2  configured to accommodate one or more recoil springs S 1 ,S 2  of the recoil system RS, for example when the rifle is outfitted with a standard caliber bolt carrier group BCG. In the specific embodiment shown representatively in  FIGS.  1 - 7   , for example, the stabilizer includes two lobes  64   a , 64   b  extending laterally from the elongated stem  28 . Each lobe  64   a , 64   b  is sized and shaped to slide into and out of a spring channel SC 1 ,SC 2  of the upper receiver UR of a Sig Sauer MCX rifle. The stabilizer  64  may in some embodiments extend below the bottom surface  28   c  of the elongated stem  28 . 
     In some embodiments, one or more wing projections  34 , 36  are disposed on the elongated stem  28  and are configured to slide within lateral channels or along guides (not shown) of the upper receiver UR. Generally, the wing projections  34 , 36  prevent the distal end of the charging handle  10  from dropping too low into the upper receiver UR. 
     In some embodiments, the top surface  28   t  of the elongated stem  28  includes one or more chamfers  29   a , 29   b . The chamfers  29   a , 29   b , when present, may improve slidability of the charging handle  10  as it is inserted and/or withdrawn from the upper receiver UR. 
     Generally, charging handles  10  consistent with the present disclosure improve operability of rifles equipped with sub-caliber bolt carrier groups BCG. Typically, an AR-15 rifle cycles 5.56 caliber rounds or .223 caliber rounds. In some embodiments, the charging handle  10  consistent with the present disclosure operates with a bolt carrier group BCG configured to cycle ammunition rounds other than a 5.56 caliber round or a .223 caliber round in an AR-15 rifle. In some embodiments, the sub-caliber bolt and carrier is configured to operate within an upper receiver of an AR-15 rifle with a bolt carrier group configured to cycle .22 caliber ammunition rounds, such as  22 LR ammunition rounds. 
     An M16 rifle typically cycles 5.56 caliber rounds. In some embodiments, the charging handle  10  consistent with the present disclosure operates with a bolt carrier group BCG configured to cycle ammunition rounds other than a 5.56 caliber round in an M16 rifle. In some embodiments, the sub-caliber bolt and carrier is configured to operate within an upper receiver of an M16 rifle with a bolt carrier group configured to cycle .22 caliber ammunition rounds, such as  22 LR ammunition rounds. 
     Sig Sauer&#39;s MCX rifle typically cycles 5.56 caliber rounds,.308 caliber rounds, 6.8 caliber rounds, or 0.300 AAC Blackout rounds. In some embodiments, the charging handle  10  consistent with the present disclosure operates with a bolt carrier group BCG configured to cycle ammunition rounds other than a 5.56 caliber round, a .308 caliber round, a 6.8 caliber round, or a 0.300 AAC Blackout round in a Sig Sauer MCX rifle. In some embodiments, the sub-caliber bolt and carrier is configured to operate within an upper receiver of a Sig Sauer MCX rifle with a bolt carrier group configured to cycle .22 caliber ammunition rounds, such as  22 LR ammunition rounds. 
       FIGS.  8 - 13    show components of the Sig Sauer MCX rifle platform.  FIG.  8    illustrates the standard charging handle CH compatible with the MCX rifle platform&#39;s upper receiver UR that does not include a bolt hook  38  having a height h of about 3 cm to about 10 cm, or a stabilizer  64  configured to slidably mate with spring channels SC 1 ,SC 2  of the upper receiver UR. The MCX rifle&#39;s ejection port cover RPC and forward assist assembly FAA are also shown in  FIG.  8   .  FIG.  9    shows the bolt carrier group BCG and recoil system RS of the MCX rifle. The recoil system RS includes two springs S 1 ,S 2  arranged side-by-side over respective first and second spring rods SR 1 ,SR 2  and between first and second spring plates SP 1 ,SP 2 . the bolt carrier group BCG includes a bolt B, a bolt carrier BC, and a firing pin FP/firing pin spring FPS configured to cycle 5.56 or 0.300 Blackout caliber rounds. An op rod OR mates with the bolt carrier group BCG and includes a bolt hook catch BHC and piston joint PJ. A firing pin lock FPL, firing pin lock pin FPLP, and firing pin lock spring FPLS are also shown representatively in  FIG.  9   . The lower receiver LR of the Sig Sauer MCX rifle is shown in  FIG.  10   . The gas valve assembly GVA and piston P are shown representatively in  FIG.  11   , along with two barrel options BA,BA′. The proximal end of the piston P buts the piston joint PJ of the op rod OR to drive the bolt carrier group BCG rearward in response to gas directed to the piston via the gas valve assembly GVA with each round fired through the barrel BA/BA′. 
     In operation, the standard charging handle CH of the Sig Sauer MCX includes a catch that mates with the bolt hook catch of the op rod, as shown in  FIG.  12   . The spring channels S 1 ,S 2  and barrel chamber BAC of the Sig Sauer MCX rifle are shown in the photograph of  FIG.  13   .