3D Printed AR15 1200 Round Update: Two Cracks in Unexpected Places (And How to Fix Them)


Gunny McGunsmith


Published on Mar 23, 2020

In this video we try out a few new camera angles, take a look at some more range footage from the AR15, and talk about two cracks which formed in some unexpected places.

Most 3D Printed AR-15's will crack at the buffer tower. This area undergoes a lot of stress due to the recoil spring and buffer tube and has been the bane of many 3D printed lowers in the past. The WWSD2020 style lower here addresses that problem by utilizing a monolithic design.

However, we encountered a couple of cracks along the upper edge of the takedown pin holes. There are a few reasons this may have occured:

1) We could've accidentally over tightened the bolts
2) They just cracked overtime due to the stress on the lower and we never noticed
3) The surface area for the bolt head and nuts are too small and washers need to be used
4) I ran it too hot
5) The threads on the bolts dig into the polymer and cause cracks

Either way, we're going to be repairing this lower with a plastic welder, some JB Plastic Weld, and sandpaper. We'll watch it closely from here on out to see if the cracks reemerge, and in future builds we'll use washers as well as different bolts/pins to see if the issue arises.

As always, thanks for subscribing, commenting and liking! I hope to see you guys in future videos!

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