I believe brownells sells two different devices to measure a chamber the first is an Overall length gauge and second being head space gauges.

Thanks Paul....I've never done this before so am checking for when (Lord willing) I can get into reloading.  I've heard that you try to space the bullet out so its within a couple thousandths of the rifling.  Is that what you understand?  Thanks again.

this is a case of numbers, remember every little bit counts. You want your loads a close as you can get.

It sounds like you are trying to check for the overall lentgh of the loaded round in relation to bullet seating depth, not headspace. If this is correct, do an internet search for a Hornady Lock-N-Load.  Hornady (formerly Stoney Point) makes a headspace guage also. The pictures on the package's pretty much show how they work. I have the O.A.L. tools and they are very easy to use. You will have to buy a modified case for every caliber you want to use it with.

You don't want the bullet any closer than .020" from the riflings.  Too close will build up higher pressures.  You can take a dummy shell and bullet and blacken the bullet w/ a black majic marker and keep seating the bullet a little at a time till the bullet shows no sign of the rifling touching the bullet.  I'd then go another .020" from there.  If you have a magazine that the live rounds needs to fit inot make sure it is seated enough.  I have a 30-06 that has a magazine and seating the bullet .020" from the riflings won't fit in the magazine.  I seated the bullets far enough to make sure they'll always fit in the magazine.  My Encore is set-up .020" off and it likes them that way.  Just remember that the shell is only going to be set-up for that rifle doing it this way.  It's not recommended to swap from one rifle to another (high pressures can be an issue).  Stoney Point does have the guage, but you'll need each individual caliber case accessory for the calibers you intend to reload.  It's not a bad idea, but I never load to the max and load only for a particular rifle in each caliber (don't have 2 rifles in the same caliber).

Resize(neck size) a fired round just enough to keep a new bullet in the caseing (finger tight) with no primer or powder then insert in chamber and close bolt.

the bullet will be pushed to the rifle threads then CAREFULLY remove the round from the chamber and measure ...you have the over all length and you can measure it for all the different bullets you use then simply load your ammo a couple of .001's shorter....more acurate and cheaper that a over all length gauge.

That's great advice - thanks!

david something I failed to mention, buy you a current reloading book and READ and UNDERSTAND before you even think of starting.

good luck

Yes...you're absolutely right.  I've had manuals for years, and they need to be updated. 

I've been studying this stuff for a long time but never had the time to get the equipment and get going.  Headspace is always something that has thrown me, especially for belted magnums.  Hopefully in the next few years I'll have the opportunity (if Obama doesn't mess things up and/or they every catch-up with primer and powder production) to start.

You guys are great. - thanks for all the help.