Lines of Effort
The jig is up!
Dedicated to the good citizens of the City of Brotherly Love.
Effort Bloomberg is the AR lower built of plastic bricks. It is likely dependent on Efforts Thumbhole or Woodstock for reinforcement of the rear upper lug pin and the location of the buffer tube. If Effort 22 succeeds, the magazine & trigger wells can be used from that effort. The most difficult part of this effort will be the location of the trigger pins and safety without drilling; a one-piece trigger pack can be used, but is rather expensive. This effort may use commercially available magazine wells, such as the Colt 901 AR adapter, or the aftermarket H&K G36 AR mag adapter. We have modified an AirSoft G36 AR magwell from Evike; the CO2 fittings have been chopped out and a Cammenga magazine fits.
Happily, as of 18 June 2015, Effort Bloomberg is suspended due to the efforts of Boris, of Shovel AK and Iron Glock fame:
The Fruity Ghost
How to modify an AirSoft mag well - bandwidth intensive
Our $35 safety, and why a standard AR safety won't fit.
A discussion about non-matching holes.
Blocking of the full-automatic sear well must be completed for all designs submitted. This can easily be done by gluing in parts spanning the width of the receiver, even if we discover the rest of the lower does not have to be glued. In a commercial lower, it is not easily convertible because the trigger well has to be extended in order to fit an auto sear; ie, the lower has to be drilled or milled. As we are an additive manufacturing process, we need to make sure that once assembled, an auto sear cannot be easily added to the firearm - hence, that section of the lower receiver must be glued.
One of our ongoing concerns has been how to line up the 5 holes on the lower receiver - the two upper lug pins, the two fire control pins, and the safety. Plastic bricks have defined dimensions, and what if one of our holes was off by 0.2"? It wouldn't work. However, glue does not have a defined dimension. We have to build a jig, and place the 10 bricks with holes in the correct place on the jig. The rest of the receiver is built around those 10 parts - 5 on each side. If two layers don't quite meet, ABS cement or another suitable expoxy is used to fill the gap.
Here is version 3 of the jig, courtesy of the Musician. Some tips. The squares are exactly one inch or 2 centimeters. For the love of God, after you print the jig, measure the square. If it doesn't measure exactly one inch (2 CM for the furriners), tear up the jig and print another one - this time scaled at 100%. The line on the right? That would be the top of the receiver. If you build higher than that, your upper is not going to fit very well.
Some dimensions, courtesy of Elmgrove.
In this thread, there's a nice illustration:
A rough draft from the Virginian:
Bricks superimposed on the design.
The Virginian's proposed method of attaching the buffer tube.
Given the ubiquity of the AR magazine, there are numerous AR magazine adapters for various conversions, even in the AirSoft world. Below are actual metal adapters:
3 AK/Galil AR magwell adapters from Texas AK Designs
H&K G36 converter
You could cut the top off a Redi-Mag
Too expensive? Cut the top off an AirSoft ICS Read Mag System from Evike.
As of September 2013, Colt is now selling the magazine well adapter on their website - for $294!
It comes w/ a standard AR buffer and spring too!
In addition to the above, any of the magazine wells or other devices considered in Effort California will also work here.
Are you looking for the Bloomberg cupcake?