This is the same my other design except it has a magazine release pin in the front to use with California compliant magazine releases that require a tool to release the magazine.
This is a simple dust cover to protect the fire control group of an AR-15 when the lower receiver is not attached to the upper. The fire control group is basically underneth a cap. The bolt catch is exposed on the magazine side. I designed it that way so I would be able to use a Gun Vault magazine lock with this. This by no means is this an air tight seal, it is just a cover so the major components are not compeletely exposed.
To use the cover:
1) Have the fire selector in safe, which means the hammer is cocked.
2) Install the cover as if you're installing the upper receiver to the lower.
I do not know what is the short/long term effects of the various chemicals used in maintaining the lower receiver has on the materials used in creating this cover. Also please refer to shapeways for environmental tolerances for the material used.
The product is the cover only. The cover cavity is based on having a Geissele SSA installed on an Ed's Tactical Armory mil spec lower receiver.
Due to Shapeways' printers you may have to file the holes a bit so the takedown/pivot pins can go through smoothly. I printed several versions of the model and each time the holes are of different measurements and goes from a circle to an oval. The observed diameters range from 0.256" to 0.244". I have the holes designed as a circular cylinder with a 0.266" diameter, but never was able to get one printed that size. The takedown/pivots should be 0.251+/- 0.001"