I have been researching on the web for DIY laser colliminator plans, all seem to use keyring lasers but point out that the laser itself is mostly spraying out and not central....... HOWEVER most gun shops have laser bore sighters, they are machined to a half of half a hair to be chambered in the rifles chamber... ie they are a precision laser..... if not then no gun owner would consider using them.
Just think of a hollow nosed bullet but instead of a air chamber in the nose, the bore sighter laser emits from there.
They cost $35.00.
Just bought one am am now heading for the workshop.
I made my Howie Glatter type collimator using the laser from a cheap ($3) "laser pen" and a holographic circle pattern attachment bought on eBay. It is not an easy job though. I removed the laser assembly from the pen and made proper metal housing for it with larger button cells. I also changed the focusing lens too. That was the easy part. Then I made another housing with 1.25"OD and radial grub screws that hold the rehoused laser in an adjustable way and also has a thread for the patters generator. The whole assembly had to be set up on the lathe so that the 1.25"barrel would run perfectly true and the grub screws adjusted unlit the laser spot had no run out several meters away.
Recently I measured the output of the laser to be 2.6mW and it seems to be plenty.
