so far i've found 3 options. The Williams one for approx $60, the one that Carlsons choke tubes sells for $20 bucks, or one i found in brownells made by Walker for $15 (which is more of a center-finding punch than a fixture). Which one is best/worth the $? Usage will be once every few years. Anyone have on of these tools for sale? My old measure and score center w/ calipers, center-punch and drill apparently isn't as infaliable as i thought it once was, so its time to invest in proper tools.