6PPC measured freebore diameter ?

[Boyd Allen]

As near as I can tell, using the pressure ring of a bullet that was reduced a little at a time (You don't want to know.) as a plug gauge, my freebore ID is about .2436" with comparable drag in the chamber and between the anvil and spindle of my micrometer. I know that this is larger than the dimensions of some chamber drawings, but I also know that no one ever chambered with a drawing, and that even if a reamer were to be dead nuts on print, that the chamber will be a bit larger. So....how many of you have actually plugged the freebore diameter of a barrel that has been chambered with your reamer, and what does your experience tell you is a good number for the actual measurement. I should add that a gizzy that was cut with the same reamer was p 2-3 tenths larger than the barrel that I measured, for whatever reason. Perhaps the setup, and bushing fit were not as carefully done. In any case, I am glad that the barrel's dimension was smaller. Thanks,

Boyd

 

[Don]

As near as I can tell, using the pressure ring of a bullet that was reduced a little at a time (You don't want to know.) as a plug gauge, my freebore ID is about .2436" with comparable drag in the chamber and between the anvil and spindle of my micrometer. I know that this is larger than the dimensions of some chamber drawings, but I also know that no one ever chambered with a drawing, and that even if a reamer were to be dead nuts on print, that the chamber will be a bit larger. So....how many of you have actually plugged the freebore diameter of a barrel that has been chambered with your reamer, and what does your experience tell you is a good number for the actual measurement. I should add that a gizzy that was cut with the same reamer was p 2-3 tenths larger than the barrel that I measured, for whatever reason. Perhaps the setup, and bushing fit were not as carefully done. In any case, I am glad that the barrel's dimension was smaller. Thanks,

Boyd

Seems very typical and right in the sweet spot to ensure accuracy, not so small in diameter that the reamer would not cut a large bored/lapped barrel but not so large as to cut an excess diameter freebore that would allow alignment problems.

Most use pin guages (Deltronics) to measure freebore dimension cut in barrel.............Don

 

[Mike Bryant]

Pin gages would be the easiest way to measure freebore diameter. You can get Deltronics pin gages in .0001" increments with whatever diameter median you want. Specify the middle pin diameter and you'll get twelve up and twelve down in size from that. I have pin gages for .22's and 6mm in .0005" increments to check neck diameters. It would be nice to have a set in .0001" steps for a .262 neck so you'd know exactly what neck diameter the barrel has. But, probably not very necessary unless you try to run very tight clearances. My last reamer has a .244 freebore after I measured the bullets I was using and had .2435" diameter bullets with a reamer that had a .2435 freebore diameter. I haven't seen any difference in accuracy by going to the larger freebore diameter. I think having the correct reamer/ die combination will help a shooter more than nit picking details. I had the privilege of shooting next to Gene Bukys at Phoenix. He shoots very hot loads. He basically told me that with the right die, you could shoot hot loads until the necks come off if you have the right die chamber combination without getting the click at the top of the bolt stroke. If you get the click, that's a sign that you don't have the correct die for your chamber. For most of my shooting career I shot using Wilson neck size dies and seaters at about 3250 fps. No brass problems, only when you are getting beat by guys shooting the upper loads do you come into problems with having to have the correct die chamber combination. The last set of Deltronics pins I bought were about $125 give or take. It's been awhile since I bought a set.