please define free bore

[mrmarmota]

First, let me say that I am a rookie. That said please help with my quandary and don't worry about talking down to me. I need to get this.
I have been looking at several reamer prints by PTG. Not one of them call out a number for free bore or even identify free bore. Lead and throat yes but not free bore. So what exactly is free bore and where does it come from? Is free bore the combined throat and lead?
Thanks in advance. I eagerly await my education.

 

[cdparker]

Here is a discussion on this subject done on this site several years ago.
http://forum.accurateshooter.com/index.php?topic=3747855.0
HTH

 

[JohnHenry]

The freebore for the attached reamer is .025(dimension "a" on the print).

http://www.grizzly.com/products/-223-Chambering-Finish-Reamer/T10175

http://cdn2.grizzly.com/specsheets/t10175_as.pdf

PS: An informative article. http://bisonballistics.com/articles/an-introduction-to-rifle-chambers

 

[mrmarmota]

That certainly clears the water .From where the case neck ends to where the tapered part of the lands start is free bore. In the shaded drawing by JGS free bore is .117.In the PTG /GRIZZLY .223 free bore is .025. Yes I can see that now.
Is there a rule of thumb for how much free bore is required for certain bullet lengths and profiles?

I recently purchased a new 30 BR Robinette reamer from Grizzly # T23216 zero free bore .This was my very first chambering. The barrel is a well used 30 BR that never lived up to its reputation . So I cut the chamber off and rechambered. Nothing ventured nothing gained. I think I did a good job but the result was the barrel did NOT SHOOT ANY BETTER. With zero free bore the seated bullet is very far back in the neck. I am assuming that reamer was designed for 118 Bibs. Totally inadequate for my bullet of choice.115 bergers and 110 hornadys. So now do I go in there with a throating reamer to create the free bore I need ?
I am eager to learn about this. I hope there is more input.
Thanks very much

 

[JohnHenry]

The freebore does not include the length(.015") of the 45* transition from the case neck to the .224 diameter cylindrical (freebore) section on the above 223 reamer print.

 

[yukonal]

So now do I go in there with a throating reamer to create the free bore I need ? Thanks very much

YES.

 

[swd]

Yes a throating reamers is what you need to cut free bore. They're handy to have. Go slow and check often until you get used to them. The feel is VERY light to find your zero and you probably won't feel anything on the tailstock when cutting.

Use the throating reamer to take the neck tension out of a piece of brass to make a seating gage. It needs just the slightest amount of tension to keep the bullet from sticking in the lands.

 

[mrmarmota]

Thanks for the responses. I am new to this game but determined to succeed .I am sure there will be questions.
Does the "throating reamer" need to have the same lead angle as the chambering reamer had?