Lethargy, procrastination and ambivalence - Part 2

August 7, 2022 – The latest shop project, a ramp in need of repair; seventeen years of bearing heavy snow weight, heavy traffic, porcupine gnawing and, finally, dry rot. It took a day and a couple of hours to strip it and pull nails.

Work on the ramp, change out some house trim, restore the pad under the generator, maintain the garden. Lots to do and, fortunately, I like to fix things. Rebuilding a ramp for less than $300 worth of lumber seems much better than a $3,200 bill from a contractor.

The AR 15 project has been pretty much the same. An accumulation of small problems caused serious reliability problems and reliability problems in a firearm slated for self defense is a nonstarter.  A little time spent inspecting and assessing identified the associated problems and only a few dollars were required to implement corrective actions.

Replacement magazines. Yes, it does say 5.56×45…

 

I picked up some 20 round PMAG GEN M3 magazines, both 223/5.56 and 300 Blackout.  The blackout version was priced 90 cents more, $13.49 and $14.39  respectively, although I don’t know why as they are interchangeable. I know the sales pitch, but if you are relying on a magazine imprint to tell the difference between magazines loaded with 5.56mm ammo and 300 Blackout ammo, further training may be needed. Really.

Why did I replace the steel magazines with polymer? Because they tend to not hold up and they tend not to be reliable under extended use. Replacing the steel magazine did not solve the short stroking problem, but it did end the rifle’s inability to feed a round when manually cycled.

Yes, I was an irresponsible gun cleaner…

However, in my defense, the rifle didn’t work reliably even before my neglect.

The rifle was shot heavily in a compressed configuration, which seems to burn off lubrication and, eventually, cover all of the components aft of the chamber with heavy soot. The carrier assembly was disassembled, scoured, lightly lubed at contact points. This step made no functional difference, but it looked a lot better and eased my guilt.

The real interloper

The adjustable gas block locating set screws were loose, or worked loose, and caused the gas block port and barrel port to be misaligned, which diminished actuating gas flow.

Both the port to the gas tube and the aft set screw measured 0.250″ from the face of the gas block to the center of the ports. The measurement from the barrel shoulder to the gas port center was 0.311″. So a 0.061″ gap was needed between the barrel shoulder and the face of the gas block to align the ports.

A 0.061″ pin gauge was inserted between the barrel shoulder and the face of the gas block and the aft setscrew location was marked.

The barrel was spot drilled to securely locate the aft setscrew, barrel and block ports and the gas block.

The original spacer was omitted, primarily because it did nothing. The handguard was left off for the first test rounds for access to the gas block metering screw. Next time I have the handguard off I will removed some material so the adjustment can be accessed without removing the handguard.

After backing out three full turns on the gas block metering screw, a twenty round magazine of 220 grain factory ammunition was emptied without a single failure to feed, jam or misfire. Yes, the magazine was in the rifle when emptied. Someone will asks.

Then the handguard was installed, the silencer was installed and twenty rounds of each type of ammo planned for use were cycled through the rifle. Again, no failures to feed, no jams and no misfires. I did not have to alter the buffer weight or springing, however, gas block adjustment was required for reliable cycling of 200 grain and 220 grain subsonic rounds.

The important point for me is that a firearm was returned to service as reliable and accurate and one gun less in queue for repair.

Handloads shot….

Most projects eventually get done. A railing and this one will be done also.