Flared base for sock grip. Stick a rubber on it, band it in place etc.
Rounded some stuff for better printing too.
Clamps on picatinny top rail. Seems to work on ARs.

oem gatalog ul IVAN release readme follows -

"This the the brass catcher Ivan has been using.
The STLs are oriented and scaled correctly.
I have been using some M3 screws and 1/4 - 28 rod to assemble the catcher. The screws are for the rail mount, the rod to attach the body to the mounts.
I drilled the mounts out to .250, and hand threaded the rod into the body of the catcher. It has held up for about 1000 round now.
I printed in ABS, it should work in PLA.
You will need to make a bag. I'll leave creation and affixing the bag to you. If you use fabric, consider using fireproofing spray on it, just in case.
I used some scrap cotton cloth and hand sewed it together to form a pouch. I then drilled four holes in the fround lip of the catcher to sew the pouch on to. You could just use binder clips or whatever is handy."

LBRY Tags: guncad; reloading