My semi-custom COAL gauge, is this fully accurate?

[c1steve]

I did not fully trust the measurements I was obtaining when trying to determine the exact COAL on my 260 bolt gun. I then used a Hornady OAL gauge, but drilled and tapped the base of a SMK 142 to 10-24. I used the threaded rod in place of the plastic Hornady rod.

The photos below show the system, which should be very accurate. Only problem is that my COAL measures 2.975, which is longer than expected. Any comments welcome.

The mags I am using are Alpha Type 2, which are 2.985 ID. If I used AI mags, I would have to reduce the COAL to approximately 2.875.

 

[Gray]

Re: My semi-custom COAL gauge, is this fully accurate?

should work fine, why were you not getting accurate measurements with the original setup though?

 

[pcschwenke]

Re: My semi-custom COAL gauge, is this fully accurate?

FYI, I made something very similar. It works fine and it's very repeatable.

 

[MALLARD]

Re: My semi-custom COAL gauge, is this fully accurate?

you can determine your ideal COAL from doing tests on paper. What your doing may not give you the type of results that a paper tests will

 

[c1steve]

Re: My semi-custom COAL gauge, is this fully accurate?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Special Delivery</div><div class="ubbcode-body">should work fine, why were you not getting accurate measurements with the original setup though? </div></div>

I could not tell if I was jamming the bullet into the lands or not. I preferred to be able to move the rod and bullet in and out to obtain a better feel for the correct position. In retrospect, a judicious amount of pressure and the using the tool correctly probably was giving me an accurate measurement.

I tried a second method, that was giving me too short a measurement. For my other calibers, I will probably just trust the Hornady system. Thanks to all for the advice.

s