Progress on the AR-pattern blunderbus

[command_liner]

The rear lug is now ready for welding onto the barrel. I started with 1" by 1/2"
hot rolled, bar stock and turned it in the lathe to 0.90". A slight cleanup on the
belt grinder and it fits right in.

Odd AR15 note: The rear lug depth is the same width as the magazine well.

To facilitate positioning, I am making the rear lug way too long. After welding the
lug on, it will need to be trimmed to fit, an easy hand operation. Yesterday and
today I took some good photos of the brute-force nature of the build.

http://www.flickr.com/photos/command_liner/sets/72157623583216070/

NOTE: URL corrected

[Rekrab]

I was just wondering about this project the other day. Good to see you haven't given up on it. Can't wait for the range report.

[command_liner]

Somehow my quick reply from last night did not stick.

Rear lug is on and trimmed down to size. It is not yet finished, and not
yet drilled. The fit and finish on this part is important because it will
determine how snug the upper-lower fit is. So I am hand filing it.

Three more pictures at the URL mentioned above.

Time passes...
I have re-discovered the definition for the term "tedious hand filing".
Or have at least empirically verified the definition. The lower now
mates cleanly with the upper.

My technique was to use a black Sharpie to mark the steel, then
check the fit, then file away the black. Repeat as needed.

Oh, and I drilled and tapped the lower for the handle -- 1/4-28.

[motorhead]

ya run what ya brung. i used to use a sharpie to seat valves.

[command_liner]

When doing mostly custom work, progress can be slow.

But now the upper is mounted on the lower. The upper has been
finished some -- I went over it with a fine radial flap wheel to buff
out all the lathe cutter marks.

The lugs are drilled for standard AR mounting pins. The 80% lower
has the front pin plunger/spring pocket milled out, so now both
pins act just like a standard lower. The non-functional magazine
release is in, as is the non-functional selector switch. A blunderbus
does not have need for a selector or magazine, but hey, they look
cool to my son so what the heck.

After using a 1/4" transfer punch to pick up the holes, I went with a 1/16
drill, then checked for alignment, then used a #3 drill. A second alignment
check showed the front good, but the back a bit off perhaps 0.010. I used
the #3 drill as a mill to bump the hole, then drilled the front to finished size
and checked. The rear was good to go, so that got drilled to final size.
The pieces snap together. The front pin retainer spring hole needed to
be drilled. Mounting that spring/plunger setup is a bit tricky. I used
needle nosed pliers and a very thin scraper to hold the retainer down
while the pin was inserted. This must be the right way to do it, because
the pin head has a flat milled in it, and that flat is oversized just enough
to fit a thin scraper or razor blade.

The trigger guard is in too, so now it is time to work on the trigger,
and refine the mechanism to make a standard AR15 trigger actuate a
percussion cap.

No new pictures. You cannot see the springs mounted inside the
lower, and the pins are not all that impressive. I have a polishing
wheel setup; after polishing the barrel will be good to photograph.

I need some nipples and caps. Due to the have-no-job problem,
buying stuff is not on the top of the can-do list.


Edit:
New picture showing the assembly.

http://www.flickr.com/photos/command_liner/4709549844/