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About LRI's M700 External Bolt Release

Posted by Chad Dixon on

It's one of the most popular receiver upgrades available for the M700: The side bolt release.

The LRI release is 100% machined from bar stock 4130 chromoly steel.  We choose this material because it offers the perfect balance between hardness and durability.  These parts are not as simple as one might be initially lead to believe.  Impact forces applied to the bolt stop's lug surface must be considered.  That energy has to be channeled to the receiver itself.  

This is where our product starts to distinguish itself.

First, our bolt stops are wider than most.  This is offer a broader impact surface to the bolt lug.  Doing so reduces the risk of the bolt's lug becoming peened and damaged during its service life of hundreds of thousands of rounds.  For this reason our bolt stops cannot be installed at the popular canted angle that elevates it above the stock line.  The decision boiled down to two choices; convenience of installation or reliability.

The balance of hardness and toughness of the bolt stop has to be measured against the hardness of the bolt's lug surface.  Too soft and the bolt stop begins to deform.  Too hard and we run the risk of damage to the bolt or the bolt stop failing due to fatigue.

Next, the small retention pin of any bolt stop is the worse possible component to transfer the impact energy to.  The small pin means it will fail violently in a short amount of time.  The challenge then becomes how to transmit energy through the bolt stop directly to the receiver with very little collateral abuse to the pin.  

Instead of a round hole in the part, we turned it into an ellipse.  Our bolt stop is built so that it will float forward and aft by a small amount.  Doing so means the impact from the bolt head is transmitted directly to the receiver.  The pin has one job;  to keep the part from falling out of the receiver.

To finish the part we contour the outside to match the radius of the action.  When properly installed, it finishes with a clean and professional installation.

The external bolt stop is nothing new.  They've been around for years as a popular upgrade.  Many smiths have taken to the idea that using an altered set screw instead of a pin is a way to offer a cleaner presentation.  Doing so certainly does allow the hole feature to be "blind"-meaning that you cannot see it from the top side of the action when the rifle is fully assembled.  

We agree that this does offer a more visual appeal, however it carries with it some additional risk.  If the pin was ever broken, there is a strong likelihood that it will become stuck in the hole.  Your gunsmith will now have a nightmare to contend with because there is no way to access it from the other side.  

Drilling the hole all the way through both sides allows for much easier removal and it is why we encourage the installation with a through hole.  While we've never experienced a failure to date, the thought of having to remove a broken and seized .0625" heat treated pin from an expensive action is a job no machinist or gunsmith relishes in taking on.

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