12g bore sight adapter

I wanted to use my 9mm laser bore sight on my 12 gauge to help set up a sight. So I built an adapter to drop it in so I didn't have to buy another laser sight. I included the Solidworks file, which can be adapted to yours. There's 3 extrusions named, main is for the width of the sight and set to 10mm default. The thru hole is for the laser to go through, mine is smaller but I have a thin tool I poke through it to get the laser out, you may need to change it's width depending on what you want to use to retrieve it. Last mine has a bit of a step down so there's a third one that's called secondary taper. if yours doesn't have that just suppress it or make it the same as main. 

It fits pretty well in the barrel, not loose but not tight, and the ridge on the bottom allows it to be extracted as well. Print how you will, personally I printed it ‘upside down’ with the top of the ‘shell’ and the bottom to make sure the hole for the laser was as accurate as possible, I also did it with no supports as I could clear any mess and didn't care about looks.