Free App for Firearms Enthusiasts

Gunsmithing expert Fred Zeglin, longtime RMOWP member from Montana, has announced the release of the free GaugeGuide app. He tells RMOWP, “This is the very first, and at this time the only app available to help folks know which headspace gauges will work for any given cartridge. There are many gauges that interchange or cross-over from one cartridge to another to safely measure or establish headspace in a gun.”

Correct headspace is important for function, accuracy, and safety in firearms, he says, adding that headspace gauges are used to insure that the chamber is cut to the correct length and that when a round is chambered it will function as designed by the maker. Zeglin recommends having the headspace checked any time you buy a used gun.

Zeglin operates 4D Reamer Rentals LTD, which rents gauges and reamers to gunsmiths throughout the U.S., and he has published two books that deal specifically with firearms’ headspace, in addition to several other books and DVDs on various aspects of firearms. Zeglin has been building custom hunting rifles for more than 30 years and has taught firearms classes for the National Rifle Association and other organizations.

The free app can be downloaded at: or from the blog section of 4D’s website, You can buy Zeglin’s books and DVD’s in the online shopping section of the website or through