AR Lower-Receiver Build: Bolt-Catch Installation

by
posted on October 13, 2015
dsc_0234.jpg

Since the rifle I’m building is destined for hunting, precision accuracy is of great importance, therefore, sharing it with one of my NFA-registered lowers is not a good idea, given the loose tolerances that will develop resulting from frequent attachment/removal of the upper and lower halves. Therefore, a better idea would be to build its own designated lower, figure a way to tighten the tolerances between the receivers and to minimize separating the receivers once they’re together.

The lower starts with a receiver I selected a stripped variant made by Spikes Tactical, along with a DPMS lower-parts kit for the remaining components necessary to complete the project—barring a few substitutions. While Towsley recommends installing the trigger group first, Grazio and I opted to knock out the more difficult task of installing the bolt, as he and I loathe setting roll pins and approach it with the same degree of disapproval as Jake and Elwood have for Illinois Nazis. The necessary parts and tools are listed below:

Parts
Bolt Catch Bolt-Catch Pin (the smaller of the two roll pins in the kit)
Bolt-Catch Plunger Bolt-Catch Spring (easily confused with the disconnector spring, although the disconnector spring is wider on one end)

Tools
Small hammer, plastic and brass tipped preferred
3S pin holding punch (optional)
3/32-inch roll pin punch
Brownells Bolt Catch Pin Punch (optional)
Painter's tape

Mask the area in front of the bolt-catch housing with painter's tape to minimize marring your receiver unnecessarily. Insert the rolled pin into the pin-holding punch, or hold it with needle nose pliers as you start it into the rear side of the pin hole, tapping lightly with the hammer to start it in the hole. Place the spring in the hole centered under the bolt catch and follow with the plunger. Install and push down on the bolt catch to compress the spring and insert the Brownells Bolt Catch Pin Punch from the left to act as a slave pin.

Using a slave pin to hold the bolt catch in place as you drift the bolt-catch pin in place partially makes up for not having a third hand to complete the irksome task.

This tool is machined to allow using it from the left side as a slave pin or to remove an installed bolt-catch pin by driving the pin out to the rear. Without, it you risk scratching the finish on the receiver. Towsley punctuates his point saying, “Trust me, I speak from experience and have gotten very good at touching up the marks. But they will always show, so not scratching the finish is a much better option.”

Using the 3/32 roll-pin punch and hammer, drive the roll pin into place, using it to push the slave pin out. Insert the pin deep enough so that it is of equal depth on each side.

There are few things in the world more evil than roll pins. Proper roll-pin punches and the Brownells Bolt-Catch Pin Punch made this portion of the build significantly less time-consuming.

Function Check
For now, make sure the bolt catch operates smoothly and does not hang up or bind. You will test it further once the upper is installed. Though it’s not difficult as it is time-consuming and potentially frustrating, with installation of the bolt catch out of the way, I’d like divert from the order of Towley’s piece once more. The next entry will cover what I consider to be the second most challenging aspect of building an AR lower: installing the dreaded pivot pin.

Latest

handgun with bullets and magazine
handgun with bullets and magazine

Review: Tisas PX-9 Gen 2 Pistol

The Wonder Nine gets reimagined with a new 9 mm from SDS Imports.

Why We Need to Encourage New Shooters to Get Training

When we can, we need to tell the new shooter that they really need to learn to walk before they can run. And then we need to help them find the kind of training that will give them the basics of safe gun handling and marksmanship.

First Look: BulletSafe Vital Protection 3 Vest

The BulletSafe Vital Protection 3 (VP3) Vest is a new and significant addition to BulletSafe’s impressive collection of life-saving products.

AAC Suppressor Brand Relaunches

Advanced Armament Company (AAC), known as “The Silent Authority” and pioneering leader in firearm sound suppression since 1994, has restructured and relaunched.

Is the .357 Magnum the Best Option for Personal Defense?

Time and data have also unquestionably revealed that when compared to these semi-auto-pistol cartridges, the .357 Magnum does a better job at stopping bad guys.

First Look: Viridian Weapon Technologies HS1 Hand Stop Laser

Viridian Weapon Technologies is rolling out a game-changing hand stop laser, the HS1, which is now available with an infrared beam.

Interests



Get the best of Shooting Illustrated delivered to your inbox.