A quick way to measure distance to the lands is a cleaning rod with a flattened jag tip or 1/4 wooden dowel. Insert the rod/dowel in the muzzle until it touches the closed bolt. Mark the rod/dowel even with the muzzle with a piece of tape, place the tape as square as possible to the muzzle just barely contacting the face of the muzzle. Repeat this process with your chosen bullet pressed into the lands (i.e. drop a bullet into the chamber and hold it in place with a pen or pencil) and mark the rod/dowel with another piece of tape at the muzzle. Measure the distance between the two leading edges of tape and you have your max COAL for that bullet given where the bullet engages the lands.
You don't mention whether the factory rounds were the same bullet as the reloaded rounds. Remember, chambers don't actually care about COAL, they care about the distance from the base of the cartridge to where the diameter of the bullet engages the lands.
The above method will allow you to determine the relating COAL when that particular bullet engages the lands.
