It's my understanding that the "throat" is the combination of leade and freebore, if any.  Am I correct?

My spell checker says that we're both wrong about the spelling of leade and freebore.

JS47 wrote on May 3^rd, 2015 at 11:57pm:


Stockerman,

This can get complicated.  There's a good bit of confusion on the definitions of leade, freebore and throat.  SAAMI says leade and throat are synonymous, which most likely originated when it was not common to find freebore in a rifle.  SAAMI also says the throat and leade are the same as "Ball Seat", a military term derived from cartridges with full metal jackets referred to as ball ammunition.

As noted earlier, leade is essentially the leading edge or sloped (ramped) portion of the rifling lands.  The angle of the ramp is called the leade angle.

Contrary to SAAMI's definition, I agree with the current definition used by many writers and firearm glossaries which defines the throat as the section that starts at the beginning of the chamber transition and ends when the lands are at full height.  Therefore, the throat includes the chamber transition step, freebore if it exists, the transition region from the freebore to leade (if the freebore diameter is larger than the groove diameter) and the leade.  

Since a picture is worth a thousand words, see the illustration below, which describes the Browning .40-65 and .45-90 throats with freebore diameters slightly larger than the groove diameters.  BTW, don't be surprised if some readers disagree with my definitions.

Also, to complicate this a bit more, some experienced shooters consider freebore and bullet jump to be the same.  I.e. if the bullet is seated to touch the leade then there's no freebore by definition.

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QuestionableMaynard8130 wrote on May 4^th, 2015 at 6:31am:


I order my reamers from PT&G and Hugh Hendrickson and thoughs are the terms that they use and that's where I learned them.

So, I can varify those two.

Frank

rr2241tx wrote on May 5^th, 2015 at 10:46am:


Tom, I’m in 100% agreement with you.  My comment stems from discussing freebore with several high-velocity smokeless shooters.  Seating the bullet to touch the lands essentially eliminates the main benefit of freebore when shooting high-velocity loads.  It's the reason Roy Weatherby is renowned for using freebore in his “magnum” chambered rifles, namely reducing the front, higher portion, of the pressure curve.  Of course, to utilize freebore for this purpose requires that the cartridge is loaded for maximum bullet jump.  If this is the bases of one’s understanding of freebore, than freebore or the benefits thereof are eliminated by seating the bullet out to touch the lands.

We BPCR shooters use freebore for other reasons.  Two that come to mind are allowing for more powder capacity and possibly aiding in bullet alignment.

Wayne

marlinguy wrote on May 5^th, 2015 at 10:15pm:


Right click on it  and add it to your dictionary. 

JS47 wrote on May 3^rd, 2015 at 11:57pm:


Speil chuckers are only useful if taken with a large pinch of salt.

--
Aonghas

I don't know whether the freebore in our BPCR rifles actually is tight enough to aid in alignment or not.  It definitely helps with added powder capacity.