Freebore - Leade - Throat - plus some small other thing?

[Taxman1002587]

I am looking at the specification/print of a 6mmBR finishing reamer-immediately after the .272 neck ends there is section .0142 long where it tapers down to the bore diameter of .2435 - then there is section .080 long called LEAD (may mean leade) and finally there is section .200 long called throat. First is there a name for .0142 section - second is the .080 lead/leade = to freebore and finally will the bullet ogive come in contact with the bore exactly where the freebore/leade/lead ends or will it come in contact at some point in the throat. The reason for the question is I have a chance to buy a recently rebarrel 223AI but between its twist rate and its length of freebore (I have seen the print for the reamer used to finish the chamber) I am concerned about the bullet base being significantly below the shoulder.

Thanks for you help and insight.

 

[wapiti25]

You have hit on sore spot of mine, long throated guns. I have ruined a 6mm BR rifle that I built to shoot 100 and 200yd bench rest. The orinal chamber was throated for 65-70gr bullets but I had to turn Rem cases to fit the neck, I got lupua brass and wanted to shoot it as is. I barrowed a reamer that would open the neck up for a no turn chamber but it also long throated it for 105-107 bullets. Their are reamers for more than one end use. I have learned to ask a lot of questions about chambers. My experience is that long throats have not been good to me, even factory rifles have not shot as good with long throats. Think about how you are going to use the gun before you buy and what bullet you want to shoot. You can make the throat longer later but a re-chamber job to shorten it

 

[fdshuster]

The very reason I spec out and buy my own reamer(s). I decide what the main bullet will be that I want to use, seat that bullet in an empty case to the depth I want, usually with the base of the bullet at the bottom of the case neck, and that "dummy" round is sent to the reamer maker, also specifying chamber neck dia. (usually a tight no-turn), and chamber overall length, usually .010" longer than max case length. It's my rifle, I paid the big bucks for the custom barrel, and for the cost of installation, and I'll decide what the critical chamber dimensions will be, not someone else.

 

[SS427]

I wish I had talked to Frank about this before I ordered my custom gun. I wanted to shoot light bullets in a 6BR and the builder cut the chamber to handle that, but I have to seat the bullets with only about .250 of the bullet in the case. With the long case of the 6BR, I would have liked to seat the bullets a little deeper in the case. I suspect the builder did this to give additional powder capacity.

The gun shots great and I suspect I'm okay, but still. Next time I know.

 

[NorCalMikie]

Nothing like having a barrel chambered to "your" dummy round! Or, have a reamer cut to "your" specs. Never mind the "off the shelf" chamber job. Build it the way "you" want it. Just ask a lot of questions before you make your move.

 

[fdshuster]

Otter: The "bad news" for your throat is that, as the throat gets longer/deeper from erosion, you will be forced to seat the bullets further and further out, eventually running out of usable case neck length. As you begin to approach that point, you may want to consider using the slightly heavier and longer flat base bullets, since they will give you more bullet/neck contact, than will the boatails. You did not mention your twist, and that will be a consideration also. The worst combination (IMO) to have would be a slow twist (1-14) with a chamber throated for the 105/107 bullets, and I've seen a few: still scratching my head, trying to figure out, why, who came up with that bright idea?

 

[Joe O]

Good thread,and info.Now I know how to get on the same page as the builder,and send a seated dummy round for each bullet weight I will shoot.
Thanks Frank