Lower Receiver Transfer Bar for Last Round Bolt Hold Open
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The original AR15 'Mil-Spec' lower receiver's last round bolt hold open feature does not function properly when modified to accommodate handgun cartridges and magazines, such as 9 mm×19 mm, .40 S&W, .357 SIG, .45 ACP, Glock, Sig Sauer, Beretta, Smith & Wesson, and Hekler & Koch, requiring manual bolt operation after the last round is fired.
Innovation Solution
The design incorporates at least two cavities in the lower receiver, with a transfer bar fitting into one cavity and a hold down into another, where the hold down overlaps with the transfer bar to secure it in place, allowing the transfer bar to be pushed up by a magazine bump to catch the bolt and hold it open until a release button is activated, enabling proper function with various handgun cartridges and magazines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the lower receiver is modified to accommodate handgun cartridges and magazines, then the firearm can use different types of ammunition and magazines, but the last round bolt hold open feature does not function properly
Solution Approach 1:
The patent introduces a transfer bar as an intermediary component between the magazine bump and the bolt catch mechanism. The transfer bar receives the upward force from the magazine bump and transmits it to the bolt catch, enabling the last round bolt hold open function to work with handgun magazines that have different internal geometries and bump locations
Solution Approach 2:
The patent divides the lower receiver into multiple cavities (first cavity for the transfer bar, second cavity for the hold down) to accommodate the new components. This segmentation allows the modification of the lower receiver structure to support handgun magazines while maintaining the bolt hold open function through properly positioned components
2Adaptability or versatility
If the lower receiver structure is modified to work with handgun magazines, then versatility is improved, but the original integrated bolt hold open design no longer functions
Solution Approach 1:
The transfer bar serves as a mediator that connects the magazine's last round bump mechanism to the bolt catch. It translates the upward movement from the magazine bump into the proper motion to engage the bolt catch, restoring automatic bolt hold open operation without requiring manual intervention
Solution Approach 2:
The hold down component is pre-positioned and secured in the second cavity to maintain the transfer bar in its proper position. This preliminary positioning ensures that the transfer bar is correctly aligned to receive the magazine bump and transmit the force to the bolt catch when needed
Data Source
AI summary
An apparatus and method for creating the apparatus that holds a bolt open after a last round is fired from a magazine is disclosed. A lower receiver may include at least two cavities. A transfer bar may be configured to fit into a first cavity of the at least two cavities. A hold down may be configured to fit into a second cavity of the at least two cavities. At least a portion of the hold down may be configured to overlap with at least a portion of the transfer bar to hold the transfer bar in place. The transfer bar, when a final round is fired from a magazine in the lower receiver, may be pushed up by a bump in the magazine to transfer upward movement to the transfer bar that catches a bolt and holds the bolt open until activation of a release button.