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Gun Build Series III

Posted by Administrator on 2/17/2015

Click HERE to view or download brochure for the BHAK54 featured in this article.

We use an end mill for the barrel pin hole as the flat end cuts into the barrel without traveling to the side by following the outside radius of the barrel. A conventional twist drill bit will travel and can elongate the hole, potentially causing in and out or rotating movement of the barrel in the front trunnion.

Using large amounts of cutting oil, we then use a precision reamer through the hole, as seen in the next picture, which enlarges the size of the previously formed hole by .005” with a very high degree of accuracy, and leaves an almost honed like smooth surface through the bore.

We cut our own dowels for the barrel pin out of chromium-vanadium hardened drill rod that is .001” oversized and slightly beveled on both ends. These are pressed in with a 20 ton pneumatic vertical press as seen in the next picture, using Never-Seez from Bostik swabbed into the hole to keep the surfaces from galling.

We install the rear sight block next. This is pressed on, and in the following image you’ll see that we use a twist drill for the pin hole. The area removed on top of the barrel where the pin secures the block is relatively small and not as critical as the barrel pin so a twist drill works well for this.

Like the barrel pin, this hole is under sized .001” as are all our pin holes, along with the OD or ID of any pressed surfaces and Never-Seez is always used so there is no galling. You’ll see in the following picture where this pin is being pressed in using a 20 ton pneumatic vertical press, as seen previously.

The next work station is a 20 ton pneumatic horizontal press that is designed specifically to install the barrel components. The lower forearm bracket is installed on the barrel and you see in the following picture where the front gas block is being pressed on next.



The components are aligned properly in their vertical positions with a sliding aluminum block that captures and holds the parts while the ram presses them on. The torque is transmitted to a stop block that goes up into the mag well against the back of the front trunnion as seen in the next picture.
The barrel is turned with elevation changes that act as stops for each of the components and after installing the bayonet lug the front sight is pressed on.


Before pinning the front sight it is sighted in on a bench rest with a laser at 30’ and rotated into the correct position with a torque handle.

After the pinning of these components the gun is now ready for initial assembly and test firing, prior to being stripped, media blasted and Cerakoted. 


In the next and final post on this build we’ll go through those steps right up to QC and packaging.