Originally Posted by Scot E
good Info. I was going to mention the collimator but the one I have is an old one and I am not up on which ones are good today. Which do you use, the magnetic one and how is the etched glass setup?
I guess my favorite collimator is the Bushnell Professional Boresighter 74-3333. It provides three adjustable arbors that grab the bore when tightened. They are accurate to within about +/4 MOA, which is OK for most purposes. This model has an etched reticle with a 10x10 grid of 4 IPHY boxes, similar to many other models. The reticle pattern needs to be calibrated, usually by measuring the grid using a mildot reticle scope that you trust. They sure make reticle measurements easy, though. They have a dozen other uses as well.
This Bushnell model also has a removable cap on the back end that allows the instrument to be calibrated if it falls out of cal (usually because someone fiddled with it). Nearly the entire country is out of stock right now waiting for the Bushnell to make more. You can find used ones on eBay.
The magnetic collimators are not very accurate, but are needed for muzzle brakes. I made my own magnetic attachment that is as accurate as the muzzle brake it's attached to.
All the other models from Bushnell, BSA, Simmons, etc., provide caliber-specific spuds that are too small. They fit the bore loosely and are not repeatable.
Alley Supply sells the best bore spuds - very precise fitting - and they can be used with any collimator. The Alley Supply collimators are well made but they do not offer a grid pattern.
I've been developing a new collimator that I hope to put into production soon. I'm working on manufacturing issues right now. The prototypes have been working great.