While you are on the site, in your browser find and click "Add to Home Screen" A CGN beaver app icon will then be created to your phone that is directly link to the site.
Note: This feature may not be available in some browsers.
Referring to manufacturers specs is going to be most accurate.
Using a cleaning rod with a tight patch and marking it as it makes a complete rotation should get you pretty close as long as the twist isn't slower than the length of the barrel.