The UBAR The UBAR is a 3D printable AR15 lower receiver. It is an evolved version of the U-Bolt Vanguard lower - easier to assemble, stronger, and compatible with a wider variety of AR15 parts. At the core of the UBAR's design is it's simple reinforcements - using hardware store metal parts, it solves the major design concerns that printed AR15 lowers face. Using a U-Bolt to reinforce the rear tower and rod end eye bolts to reinforce the front takedown lug, the UBAR is a contender for the strongest printable AR15 lower design at it's time of publication.

Printed Parts Checklist:

UBAR2 Lower Receiver
	Eight variants are avaliable:
	Four of the variants are the UBAR2, four are the UBAR2C - the "C" designation indicates that the lower has a little extra clearance that is require for some sidecharging/billet/nonstandard uppers.
		
	Both UBAR2 and UBAR2C have four sub-variants - there are high-shelf options and low-shelf options. If you plan on using an FRT trigger, or other device that requires a low shelf receiver, print one of the low shelf models. Otherwise, the standard lowers will be stronger (since lowering the shelf increases a stress concentration in the lower).
	
	For all the high and low shelf variants, there are two sub variants - lowers that have a cutout for the forward assist, and lowers that do not. If you have a forward assist installed on your rifle, print the forward assist version. If you have a sidecharging AR, one without a forward assist, or you removed/plugged your forward assist, you can print the no forward assist version, as it will be slightly stronger.

Hardware Checklist:

Refer to the "Shopping List" section of the build tutorial pdf.

General Print Settings:

This receiver has been tested to work well in eSun PLA+. In any material similar or superior to PLA+, this receiver should work as well.

Note that all STL files are oriented and scaled properly, and changing their scale or orientation may result in your parts not fitting/working properly. Note that you should follow these print settings in order to get the best possible results - changing nozzle size or layer height may cause you to have to hand fit things!

My print settings for PLA+ were as follows:

Walls: I used 8, but you're free to use whatever works best for your setup.
Nozzle: 0.4mm
Layer Height: 0.15mm or 0.16mm
Temp: 230/60C
Infill: 100% Recommended - while the UBAR might not need 100% fill, this ensures that you won't end up hurting the lower if you overtighten anything.
Supports: On/full (tree supports are ok)
Cooling fan: 20% normal, 50% on bridges. Off for the first 10 layers. Keep the fan speed low to prevent warp.
Bed Adhesion: gluestick or hairspray recommended

All other settings can/should be left as default or whatever you know works best with your printing setup