please explain

[SPM]

Hey men, I thought I had a handle on this freebore stuff but maybe not. My 6br reamer has a .060 freebore and it will basically shoot up to 70gr bullets, and if I want to shoot heavier bullets I would need more freebore right? So my question is how can you have a chamber with zero freebore?

Thanks,

SPM

 

[JayIdaho]

Freebore is the cylindrical section, bullet diameter or a couple thou more, between the end of the neck and where the leade begins. If the leade begins at the end of the neck, you have zero freebore.

 

[Cheechako]

We need to get our nomenclature correct.

Most reamer grinders will call freebore and lead the same thing, although on most reamer prints it is labeled as the lead. The tapered portion in front of the freebore/lead is the throat.

To your question SPM. No, you do not necessarily need more lead for the longer bullets although it is certainly the preferred way to go. You can simply seat the bullets deeper in the case. Most shooters will have their reamer ground to accomodate their favorite bullet but most other bullets in that same weight range will work almost as well.

It is possible to have a chamber with zero lead but it will only work with certain bullets, such as bore-riders.

Ray

 

[SPM]

Thanks guys, and this may be a stupid question, but how do you know what bullets work with zero freebore? SPM

 

[Cheechako]

SPM

A bullet seated in a zero lead chamber would have to seated such that only the ogive portion would extend beyond the case neck. With most bullets this would not be very practical. Possible, yes. Probable, no.

On the other hand, a bore-rider type bullet has two diameters. The base is groove diameter and the front is bore diameter. Many bullets that are unusually long for their caliber work best as a bore rider.

A photo of a cartridge with a bore rider type bullet follows. The bullet is seated such that it will work in a typical chamber with a reasonable lead. If used in a zero lead chamber the bullet would have to be seated deeper in the case, so that the larger diameter portion is inside the case neck.

Confused yet? This is harder to explain than I had anticipated.

Ray

 

[Cheechako]

SPM

Gunamonth is correct. There are many custom chambers that have little or no lead. My own 6PPC reamer is ground with only .030" lead. These types of chambers will usually have long throats with angles as little as 1/2 degrees in order to accomodate the bullet.

On the opposite side of the coin, there are many custom chambers with a great deal of lead. As an example, again, my long range 300 Short Ackley Magnum has a .300" lead to accomodate the 210 grain Berger VLDs.,Weatherby rifles can have a lead close to 1/2 inch in length but it is for a different purpose - to reduce pressure.)

However, keep in mind that these chambers are custom, most often for Benchrest rifles, are made for one or two custom bullets, and are not your average hunting or general shooting firearm. A lead in those is typically in the range of .100" to .150" with throat angles of 2 to 2 1/2 degrees or more.

Ray

 

[SPM]

Men, thanks for the replies. It all makes sense to me now. You guys keep it up and I will graduate from dangerous to mediocre.

Thanks again,

SPM

 

[Cheechako]

SPM

If you get to mediocre you'll be way ahead of most of us.

ray

 

[chino1969]

SPM

If you get to mediocre you'll be way ahead of most of us.

ray

Ray,
As usual, you always bring something interesting to the table. This is the first I've ever heard of or seen a bullet known as a bore rider. Thanx for sharing the info.
Chino69

 

[Cheechako]

chino

Bore rider, or two diameter, bullets have been around a long time.

Most artillery projectiles are bore riders. .50 BMG match shooters use them a lot. Nosler used to make them for some of the big caliber long bullets like the 300 grain .338. I'm sure that some of the "modern" bullet designs include them also although I don't keep very up to date on that stuff.

Ray

 

[JayIdaho]

The nomeclature is truly confusing but Ray has it figured out. This is from the Winchester website:

"The 5.56mm and .223 Rem chambers are nearly identical. The difference is in the "Leade". Leade is defined as the portion of the barrel directly in front of the chamber where the rifling has been conically removed to allow room for the seated bullet. It is also more commonly known as the throat. Leade in a .223 Rem chamber is usually .085". In a 5.56mm chamber the leade is typically .162", or almost twice as much as in the 223 Rem chamber."

Freebore is not mentioned.

 

[Stonewall]

A good example of a "bore rider" is the original 140 gr Winchester .264 Win Mag factory load . The 100 gr factory load was quite short and the rifles made were throated for this. The 140 gr round has a smaller diameter in front of the neck that allows this bullet to be seated father out and still work well in that original short throat.
Glenn