I did see different tools.
Again: A man built 4 magnificent rifles; he does not know what happened but one of the rifles had a problem. There was nothing suspect about him or the smiths that could not help him but one day he found his way over here.
He wanted to know where would I start when trouble shooting the rifle. I informed him I would start by determining the length of the chamber from the bolt face to the lands. I was not concerned with the length of the chamber from the shoulder to the bolt face because he had 200 fired wildcat cases.
He hoovered over the computer looking for methods and techniques for ways of measuring the distance from the lands to the bolt face. Final he came up with what I would call a contraption.
Anyhow: I took a few of his formed cases and drilled the primer pocket/flash holes out to the diameter of a cleaning rod, I then neck sized his cases to increase bullet hold ( I am the fan of al the bullet hold I can get). Once I secured the biggest, heaves and longest 7mm bullets I had in the case neck I removed the bolt,chambered one of the test cases and then inserted the cleaning rod in the drilled out case head.
And then I started pushing the bullet out of the case, the bullet came out of the case neck and traveled and traveled and finally hit the rifling,
It was about that time I explained his problem to him; too much free bore. He wanted to know how much free bore, I explained to him it did not matter, the problem could not be fixed with a 7MM shooting Time Western or anything H&H or Weatherby. He knew he would have to start over with lengthening the magazine or moving the barrel back etc.. He wanted to know how something like that could happen. I suggested someone decided they could increase the length of the throat to get more powder or they wanted to give the bullet a running start. Giving the bullet the running start decreases pressure.
So? The tool I use to transfer the dimensions from the chamber to the seating die is the same tool I use to determine free bore. I drill out the flashhole/primer pocket, I size the neck for good bullet hold. I seat a bullet, remove the bolt and slide the transfer into the chamber. After that I start pushing.
Pushing the bullet out of the case neck is a rare occurrence. Normally the bullet stays in the case neck and stops at the rifling. Once the bullet contact the lands there is nothing to be gained by showing off. A reloader that can measure the distance from a datum to the case head can measure the distance from the ojive to the case head. The difference is some reloaders believe using ojive instead if datum makes them sound cool.
Me? I always want to start out by knowing the two diameters of the barrel.
F. Guffey