Category: Builds

Back for the second half of the build.

The stripped upper on a bench block preparing to install the forward assist.

Completed upper with the tags for the parts used. The customer is left handed and may run the charging handle from the right side. In that case the use of the FCD Low Drag Forward Assist means less chance of scraped knuckles during a malfunction clearance drill.

A view showing how minimalist this forward assist is.

Before and after of the feed ramps on the Criterion Barrel.

Initial dry fit of the barrel to the receiver. Went back and opened up the right edge of the right ramp. The left ramp was okay. Don’t really want to take the anodizing off the ramps in the receiver as that makes them prone to being damaged.

Prepping the bolt to check headspace. This fixture makes it easy to remove the pin holding in the ejector. The ejector can give a false feel during the headspace check.

Stipped bolt ready to check headspace.

My headspace gauges are on the bottom of the picture. Since this picture I have added a proper 5.56mm headspace gauge. The barrel did pass the .223 Remington GO gauge. It also passed by not closing on the 5.56mm max gauge.

Nicely dimpled by Criterion

SLR Jig to add a second dimple. Why? Because your gas block can’t be too secure.

After the jig.

Cold blued he spot for appearance and corrosion protection.

Used Loctite 620 Bearing Retainer to bed the barrel to the receiver. The bearing retainer will swell slightly, filling any excess space, and lock the the two together improving the rifles consistancy.

Barrel and receiver hand tight. Waiting for the bearing retainer to set up.

Gas Block

Installing the Sionics Mid-Length gas tube.

Just enough of a second dimple for the set screw to dig into.

Original set screw.

The knurled set screw I actually used. In addition to the knurling I also used VC-3 to insure the screws don’t loosen.

Torquing the barrel nut on the Midwest Industries Slim Line Combat Rail to 40 foot-pounds. This is the 15 inch version. I really like that the barrel nut for this line of handguards doesn’t need to be timed to the gas tube.

Torquing gas block set screws to 30 inch-pounds.

Fully assembled gas system.

Testing that the BCG not impeded by the gas tube. It passed with no interference from the gas tube. This will maximize gas tube and gas key life.

Customers choice for a muzzle device.

Hand tight to the crush washer.

Tightened till the marks aligned.

Almost finished. Most of the hard stuff is on.

Even though its probably not needed. I still used the rail alignment fixture to make sure the rails are straight.

Torque tab installed. Keeps the handguard from coming off and prevents over-tightening of the screws.

Setting the torque.

Following instructions.

Assembly complete. only a few more parts to add.

Starting top see what the final product will look like.

This is one of the last parts.

First assembly. Hope the customer likes it. Just have to add a few accessories.

Its not loaded. Just waiting on BUIS from Midwest Industries.

This is how a build starts, with just a stripped receiver. For this build I will be using a receiver with my company engraved on it.

Started with the Low profile Magazine Catch from Forward Controls Design (FCD).

Paired it with a Enhanced Magazine Release also from FCD.

More FCD parts. This time their Augmented Bolt Catch/Release. The pads are a little bit bigger and slightly angled to manipulation more positive.

Next up were the take down and pivot pins. These pins from FCD are .040 longer than normal and made of better steel. It may not seem like much, but that extra length is appreciated when all you have are your knuckles to knock those pins through.

Here you can see the set screw used to capture the spring for the take down pin and the VC-3 from Vibratite. The screw keeps the spring from getting launched into the great beyond, should the customer chose to change the end plate and not realize there is a spring there. The VC-3 is used to keep the receiver extension from possibly rotating during castle nut torquing, or during hard use. It’s not as “rigid” a connection as Locktite type products would be, in that you can still adjust the parts after it has set up.

The receiver extension ready to be installed. I used a castle nut from FCD, which has more and deeper notches allowing for more secure staking. Grease is used in order to get the proper torque value and to prevent galling between the dissimilar metals. The end plate is from Midwest Industries and has a QD socket in it. I like to include this version in my builds so that the option to attach a sling at the rear of the receiver is already there.

Just waiting for the VC-3 to set up overnight, and the packaging for the parts.

Receiver Extension fixture used to torque the castle nut.

Mark from spring loaded center punch.

First stake finished.

Start of the second stake.

Second stake finished, as per the manual. Don’t have to worry if this will come apart under hard use.

Bravo Company Manufacturing (BCM) Trigger Guard. The button head screw for the front is an idea I got from a builder page on Facebook. I think it looks good enough to make it a standard for polymer trigger guards.

Checking the springs on the ALG Defense QMS Trigger.

Trigger and disconnector installed. The grease is on the sear surface. You may also notice how the bolt catch tilts away from the receiver a bit more than normal.

A lot of work since the last picture. Forgot to take pictures a long the way. The hammer has been installed and being tested against the block. For parts longevity avoid dropping the hammer without some sort of cushion. If you let the hammer fall full force against the receiver wall or the bolt catch it can damage them over time. You can use your thumb, foam ear plug, or a purpose built block like I have here, just slow the hammer down some how. This only applies when bolt carrier group is not there to take the blow. Such as this picture when both halves are not attached or when the receivers are “shotgunned”. Most AR rifles should not be damaged by dry firing in an assembled condition, like used for reinforcing marksmanship fundamentals.

The pistol grip is also from BCM it is the MOD 0 version since the end user has small hands. This will manipulating the controls a little easier.

The safety you see here is not the permanent one its just a place holder until the ambidextrous one comes in.

After the addition of the Magpul CTR stock the lower is finished. I will cover the build up of the upper receiver in another post.