I hear the term free bore a lot in the benchrest crowd. I think i know what is is but maybe someone here could help me figure out for sure what i means, Also how do you measure your freebore? Thanks Lee
Gunsmithing what is free bore?
- Thread starter skeetlee
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Re: what is free bore?
freebore is very similar to lead in the throat. I think it is most commonly used in association with Weatherby cartridges which allows the bullet to jump a considerable distance before it contacts the lands. This was done to allow some of the chamber pressure to bleed off right after ignition. You could measure the freebore distance in a weatherby chamber by using a rod down the muzzle and measure the difference between a bullet pushed into the lands and the distance from muzzle to the bolt face. You can use this same method on a chamber that was chambered for a standard cartridge, and if the 'freebore' wasn't too great, you can use stoney point or hornady OAL gauges to tell you the distance.
Dave
freebore is very similar to lead in the throat. I think it is most commonly used in association with Weatherby cartridges which allows the bullet to jump a considerable distance before it contacts the lands. This was done to allow some of the chamber pressure to bleed off right after ignition. You could measure the freebore distance in a weatherby chamber by using a rod down the muzzle and measure the difference between a bullet pushed into the lands and the distance from muzzle to the bolt face. You can use this same method on a chamber that was chambered for a standard cartridge, and if the 'freebore' wasn't too great, you can use stoney point or hornady OAL gauges to tell you the distance.
Dave
Re: what is free bore?
think it was a skynyrd song.
or it may be the distance the bullet actually travels before it contacts the rifling.
think it was a skynyrd song.
or it may be the distance the bullet actually travels before it contacts the rifling.
Re: what is free bore?
Hi the free bore as stated above is the distance from the ogive on the projectile to the point that the projectile will engage the rifling. That is the technical way of using the term, the free bore then will change with the length or type of projectile loaded so when talking about it people usualy are talking about the throat in the bore.
from the front of the chamber there is a 45 degree chamfer from the case mouth stepping to the throat/freebore then there is a taper from 1 degree to 4 degrees depending on the specification.
in benchrest the freebore is usualy very short as they run projectiles into the lands and they use short bullets. but for long range benchrest it is also usual to run the projectiles into the lands but we use longer vld projectiles so the freebore has to be longer to make sure the projectile is not to far into the case.
i will give you an example of 2 223 reamers we have, the first is a hunting reamer and it has 25 thou freebore it is designed for a 12 twist 223 shooting up to 55gr polymer tipped projectiles. the other reamer has 150 thou freebore as it is used with longer projectiles up to 90ge for long range varminting or F Class where 80gr projectiles are manditory here.
So you can have a reamer specified with almost any freebore length the Wby cartriges have a long freebore that is up to 200 thou longer than the length the projectile is loaded to so it is past 300 thou in some cases the reason Wby do this is they load to very high pressures and when they began to do so the powders were not as slow as available now that it reduces the engraving pressure substantualy to allow them to load to higher velocity. using the newer powders you can duplicate the older loads `with less pressure and less freebore making the rifle to technicaly be more accurate. most target type rifles shoot the best with the projectiles very clost or into the lands so having the freebore length specified for the rrojectile being used is important.
But factory chambers usualy have a throat longer than required to allow any factory loaded projectile loaded to max OAL to still be away from the rifling to make sure rifles dont blow up. Have a look at a round nose projectile of say 180gr in 30 cal then a match projectile of the same weight in the same chamber the round nose will be closer to the rifling than the match projectile if they are both loaded to the same oal.
Hope this helps
Hi the free bore as stated above is the distance from the ogive on the projectile to the point that the projectile will engage the rifling. That is the technical way of using the term, the free bore then will change with the length or type of projectile loaded so when talking about it people usualy are talking about the throat in the bore.
from the front of the chamber there is a 45 degree chamfer from the case mouth stepping to the throat/freebore then there is a taper from 1 degree to 4 degrees depending on the specification.
in benchrest the freebore is usualy very short as they run projectiles into the lands and they use short bullets. but for long range benchrest it is also usual to run the projectiles into the lands but we use longer vld projectiles so the freebore has to be longer to make sure the projectile is not to far into the case.
i will give you an example of 2 223 reamers we have, the first is a hunting reamer and it has 25 thou freebore it is designed for a 12 twist 223 shooting up to 55gr polymer tipped projectiles. the other reamer has 150 thou freebore as it is used with longer projectiles up to 90ge for long range varminting or F Class where 80gr projectiles are manditory here.
So you can have a reamer specified with almost any freebore length the Wby cartriges have a long freebore that is up to 200 thou longer than the length the projectile is loaded to so it is past 300 thou in some cases the reason Wby do this is they load to very high pressures and when they began to do so the powders were not as slow as available now that it reduces the engraving pressure substantualy to allow them to load to higher velocity. using the newer powders you can duplicate the older loads `with less pressure and less freebore making the rifle to technicaly be more accurate. most target type rifles shoot the best with the projectiles very clost or into the lands so having the freebore length specified for the rrojectile being used is important.
But factory chambers usualy have a throat longer than required to allow any factory loaded projectile loaded to max OAL to still be away from the rifling to make sure rifles dont blow up. Have a look at a round nose projectile of say 180gr in 30 cal then a match projectile of the same weight in the same chamber the round nose will be closer to the rifling than the match projectile if they are both loaded to the same oal.
Hope this helps
Re: what is free bore?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">think it was a skynyrd song.</div></div>
For a minute I thought I was on ARFCOM...
John
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">think it was a skynyrd song.</div></div>
For a minute I thought I was on ARFCOM...
John
