Paul Leitner-Wise of Leitner-Wise LLC has published a teaser for an upcoming new improved AR-15 bolt carrier called Long Advance Bolt Carrier. At first glance, it may look completely identical to any standard bolt carrier, however, that’s because the changes are incorporated into the cam track geometry which is probably not something you can spot right away unless you compare it to a standard bolt carrier.
The cam pin track shape has been refined which resulted in the bolt opening at 22.5 degrees of rotation as opposed to the 20.7 degrees of the standard mil-spec BCG. According to Paul, this almost 2-degree difference is what allows the bolt to open at a proper time and angle preventing the cam pin from contacting the internal surface of the upper receiver. Here is how Mr. Leitner-Wise describes the Long Advance Bolt Carrier and explains the benefits gained from its design.
Long Advance Bolt Carrier
US Patent Pending
Have you ever wondered why the cam pin on AR style weapons gouges the inside of the upper receiver? Over the years we’ve heard many theories for this; it’s normal, it’s caused by torque, it’s the gas system, it’s the cartridge.
None of those are correct.
While there have been attempts in the past to address this issue from variously modified cam pins to steel receiver inserts, they are all just Band Aids and do nothing to correct the inherent problem.
At Leitner-Wise LLC, this wasn’t good enough – we wanted to know what was going on.
In the end, the cause and solution was simple to identify. The original cam path design, faithfully copied for well over 60 years was drawn incorrectly. The bolt opens too early and the cam pin is able to strike the receiver wall.
By correctly mapping the cam track, we were able have the bolt rotate to a full 22.5 degrees before opening, thus avoiding contact between the receiver wall and pin. The benefits of this modification go beyond aluminum shavings in the receivers of the firearm. Locking and unlocking are smoother, there is less mechanical stress, leading to greater shot to shot consistency and due to a slightly longer unlocking phase, reliable cartridge extraction is improved in faster cycling weapons.
While the improvements are subtle it’s important to note that for the first time since their inception, AR style weapons can operate as originally envisioned.
We currently have ten Long Advance Carriers available for test and evaluation and initial production will commence shortly.
Price to be announced but commensurate with other high quality bolt carriers.
We’ll be following the development of this product and will report about its release. Stay tuned!
Images by Leitner-Wise LLC