zero free bore any advantage
- Thread starter English
- Start date
alf
Silver $$ Contributor
Two reasons come to mind.
One is if you want to shoot nothing but lighter, shorter bullets exclusively. I have a 223 reamer with zero freebore with the intent of shooting only the 40 grain Ballistic Tips.
The other reason is to have the gunsmith throat your chamber to match the intended bullets with a separate throating reamer.
One is if you want to shoot nothing but lighter, shorter bullets exclusively. I have a 223 reamer with zero freebore with the intent of shooting only the 40 grain Ballistic Tips.
The other reason is to have the gunsmith throat your chamber to match the intended bullets with a separate throating reamer.
English: I do prefer zero freebore on my chambering reamers that I buy, depending on the primary bullet to be used and the case neck length. On a case like the 223 Rem. that has a very short neck, you only have .203" of neck length and with any amount of freebore you will use up a good portion of that before erosion develops. In a short time you cannot touch the lands & keep the bullet in the case neck. When spec'ing out my reamers I tell the reamer maker I want "X" bullet to touch the lands with the base of the bullet ( the full shank diameter if it's a boatail) just a few thousandths in front of the neck/ shoulder junction. I did run into trouble one time when doing a 204 Ruger chambering. Set it up with zero freebore, it would not shoot, had my 'smith use a throating reamer to add .060" & there was a very noticable improvement in groups sizes, so sometimes you can get in trouble, but it can be corrected, as Alf said. I've also had chambers cut with zero FB, used shorter bullets when new, then as erosion created a longer throat, switched to longer bullets. That has worked well on some ctgs. One of the reasons I have little use for most factory chamberings: You have no choice on how much FB you will get, and most times it will be overly long.
English said:
Depends on the cartridge.
My 30BR shoots exceptionally well with Zero freebore. My 6PPC likes 45/1000ths.
For these two cartridges, the science/physics have been worked by some very smart people over a number of years.
If there's one thing I've learned over the last few decades it's ... don't mess with success.
As allready been stated , I think it depends on what cartridge and what bullets you want to shoot.
in the slow twist 6BR with any thing from a 55 gr to a 70 gr bullet i would highly reccomend zero free bore.
I really like it..But it really depends on how much powder you want to burn, I had 6BR slow twist with a long throat it shot well and i can see where alittle more boiler room could be of help in a varmit rifle but after having three barrels chambered with a zero free bore i would never change.
my 6BR with zero free bore a example would be a 65 gr hornady v-max is in the neck around 7/8 of the neck or slightly above the shoulder junction, you still can jump the bullet if you want to, I know for sure .010 and my guess would be @ .030+ before you started below the shoulder neck junction. That is just a example so you under stand that the free bore is really dependent on the neck lenght of the cartridge and the bullet you want to use. most of the bullets i shoot in the slow twist 6BR are 65-68gr custom's and i like to be slightly touching to .010 off and the zero FB works good with most any bullet that i would shoot.
in the slow twist 6BR with any thing from a 55 gr to a 70 gr bullet i would highly reccomend zero free bore.
I really like it..But it really depends on how much powder you want to burn, I had 6BR slow twist with a long throat it shot well and i can see where alittle more boiler room could be of help in a varmit rifle but after having three barrels chambered with a zero free bore i would never change.
my 6BR with zero free bore a example would be a 65 gr hornady v-max is in the neck around 7/8 of the neck or slightly above the shoulder junction, you still can jump the bullet if you want to, I know for sure .010 and my guess would be @ .030+ before you started below the shoulder neck junction. That is just a example so you under stand that the free bore is really dependent on the neck lenght of the cartridge and the bullet you want to use. most of the bullets i shoot in the slow twist 6BR are 65-68gr custom's and i like to be slightly touching to .010 off and the zero FB works good with most any bullet that i would shoot.
Also on repeater firearms too much freebore will not allow you to seat to jam length, which many secant ogive bullets prefer, and still fit the magazine.
I have a 6BRX 14 Twist with 0.030" freebore. 58 GR VMax bullet is only about .035 - .050" into the neck. It till shoots good for a varmint rifle. 70 Sierra BK is all the way in the short neck of the 6BRX. Zero freebore doesn't mean you cannot have jump. You can push the bullet in as far as you want. I believe that zero freebore still has a tapered throat leading into the lands. Without checking I am sure the SAAMI drawings show a freebore length and a throat length. I wish I had zero freebore. It isn't unusual a lot of people have it with light bullets. If you have a long freebore and light bullets you may have to barely seat the bullet in the neck to get .010" jump. The bullet manufacturers can recommend a freebore for the bullets you intend to shoot.
Go to the SAAMI website. Look up a cartridge. The tapered throat is almost as long as the freebore. One cartridge I looked at had .155" freebore and .1088" throat before the rifling. The throat typically has a 1.5 degree taper from the freebore to the rifling.
http://www.saami.org/specifications_and_information/index.cfm
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Dusty Stevens
Shiner
The advantage would be getting the correct freebore for the bullet you intend to shoot. Zero freebore means different things in different cases like a 118gr 30cal in a 30br needs zero freebore. A 68gr bullet in a 6br will do fine with zero. Step a 6br up to a 105gr and i dont think youll like zero due to the bullet taking up half the case capacity and being below the neck shoulder junction- neither of which is desirable nor conducive to accuracy or efficiency. So freebore really isnt a style or way of life its a measurement of where you want a particular bullet to sit in the case.
NorCalMikie
Gold $$ Contributor
Zero freebore gives you the advantage of shooting the lightest bullet you can find and going heavier as the throat wears AND, it will, sometimes faster than you expect. Nothing worse than using your favorite bullet that shoots bug holes and before too long, it won't shoot because you can't reach the lands and still have enough bullet/neck contact. Small caliber rounds seem to prefer a short throat compared to larger calibers like 30 on up. H.S. Precision chambers some of their larger calibers (.308) with lots of jump to the lands like .50 +. Some of the bigger stuff, much more.
It allows you to seat some bullets near or at the lands that otherwise would not be seated with enough neck contact.
It prevents you from seating some bullets shallow enough to get the best perfomance from them until enough throat erosion has occurred.
It prevents you from seating some bullets shallow enough to get the best perfomance from them until enough throat erosion has occurred.
SAAMI specs for 30-06 And 300 Win Mag show zero freebore for both. Several others also have none.
It's more seen for cartridges with a greater neck to body length ratio so they'll function reliable in standard length box magazines with a wide range of bullet lengths.
Bullets typically deform less when gently pushed into the throat and then fully into the rifled bore. Excessive freebore allows bullet velocity to increase so they slam into the rifling often deforming them so they're more unbalanced.
Precise bullet starting is akin to playing pool. How precise do you want the cue ball to roll?
It's more seen for cartridges with a greater neck to body length ratio so they'll function reliable in standard length box magazines with a wide range of bullet lengths.
Bullets typically deform less when gently pushed into the throat and then fully into the rifled bore. Excessive freebore allows bullet velocity to increase so they slam into the rifling often deforming them so they're more unbalanced.
Precise bullet starting is akin to playing pool. How precise do you want the cue ball to roll?
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Dusty Stevens
Shiner
Go ahead and get a zero freebore reamer to shoot like a 105gr in a 6br. By the time the throat erodes enough to make a change on any case its time for a new barrel
I'm no expert, but I think you may be on to something with the pressures, especially with the smaller bores. Take the 204R. Mine has an ungodly amount of freebore in the factory barrel. Somehow they shoot amazingly tiny groups with very long jumps to the lands too. My Savage LRPV shoots 32gn VMaxes into the low teens jumping close to .080" I think they cut them long having something to do with being able to load the hot loads to get that advertised 4,000+fps without getting into dangerous pressures. I think the bigger the bore the better for short throats. I have nothing to back this up just my tiny brain no doubt over thinking as usual.
Note most SAAMI specs for chamber length dimensions have a + .015 inch tolerance.
What is the main objective for running hot loads? Exactly, what is a hot load?
The zero length freebore in 30-06 and 300 Win Mag SAAMI spec chambers never prevented anyone from running all sorts of loads in them. Some think belted cases are stronger and therefore suitable to load hot.
There's different opinions about what a hot load is. Those who have fired proof loads 30% to 40% above normal maximum safe PSI levels know the fired case appearance is often a poor indicator of peak pressure. Therefore, all sorts of information will be put in print.
The Flat Earth Society believes the earth is almost a perfectly flat disk with the sun only 3000 miles up. The sun is a giant spotlight moving its beam around the earth. The outer edge, Antarctica, has government agents preventing everyone from going all the way to the edge (south pole) so they won't fall off. And the shortest distance from the Falkland Islands to Australia is to go straight north over the North pole then south. They also reason all the trips by man to the moon are special effects in government controlled movie studios.
I believe some reloaders' reasoning is akin to that of TFES members. Note that Hornady's velocity numbers for their 204 Ruger cartridges is attained with powder not on the market. SAAMI lists it at 57,500 psi with freebore about .090 inch. Compare that to the 308 Win at 62,000 psi with about .160 inch freebore. The 22-250 is 65,000 psi with .060 inch freebore. Therefore, the 204 Ruger is a cool cartridge, not a hot one. If your loads are matching its velocities, their pressures are likely higher than specs.
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Dusty Stevens
Shiner
What ever happened to that guy that was going to somehow prove the earth was flat by flying that rocket made from an old datsun? He was in arizona or cali and was on the news not long ago.
Just found this...
https://www.iol.co.za/news/world/flat-earthers-attempted-launch-crushed-by-gravity-13156589
Shaquile O'Neal joined the Flat Earthers last year after driving cross country and not noticing altitude changes. That was not "slam-dunk" reasoning.
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I just received my 12" Twist cut rifled bbl for my 22/250 .I intend to shoot 53gr V-max-60gr V-max or Nosler BT. This is my varmint/predator long range full soda POP cans rifle. I don't want to turn necks. Can I get no free bore or do I have to get a standard SAAMI chamber if I don't want to turn the necks ?
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