light em up

New Member
Jul 13, 2002
I have seen posts before in regards to the freebore found on Weatherby rifles... I do not plan on customizing my rifle like a lot you guys do; however, my question for anyone who would like to respond is: How concerned should I be with the freebore? How much will it affect the rifle's accuracy? I just got the rifle last fall and have been working various loads, but now I am concerned with wether or not I will even be able to get the accuracy at long range distances that I was hoping for with the factory tolerances. Obviously it can't be that big of a factor or weatherby would be concerned about it.. Any responces will be greatly appreciated.
I'll probably stir up some stink but here goes- freebore is generally not good for accuracy. I believe Weatherby does it because they think it increases velocity. Which in actually decreases it- the "open" area (freebore) could allow gas to escape around the bullet and decrease pressure thus decreasing velocity.
The reason this is bad for accuracy is the bullet slams into the lands and can cause the bullet to deform unevenly- canting it in the bore. As the benchrest boys have shown us most bullets shoot the best either in three positions: 1-Barely off the lands, 2- Lightly touching them, or 3-Seated firmly into the lands. When bullets are seated like this they are "pushed" into the lands, hopefully engraving straight and true with the bore.
But to further confuse the situation, I have a Howa factory rifle in .223. For those of you who don't know, Howa made actions for Weatherby for awhile. My Howa has an incredible amount of "freebore." Using the Stoney Point OAL guage and a 55gr Sierra BlitzKing to find the lands, I dicovered that left only the boattail of the bullet in the case neck. Seating the bullet as far out as the magazine would allow the bullet was over .100 away from the lands. The whole point to this windy story is the silly thing is a solid 1/2 MOA rifle and I regularly shoot prairie dogs out to 500 yards with it. So go figure!
To sum it up- shoot your rifle at different ranges and let it tell you if it's accurate or not.
Hope I didn't make it worse....

[ 07-14-2002: Message edited by: chris matthews ]
Hello Light em up

There are two surfaces in the bore that contribute to the length of freebore.
The first being the freebore area, and the second being the throat. The throat area is a variable because of different Ogive's. Depending on the ogive radius and throat angle this will determine where the bullet will actually touch the lands and must be added to the overall length of the freebore also.

Usually the length of the freebore is somewhere in the neighborhood of .5 through to 2 times the diameter of caliber (most factory rifles), however Weatherby rifles are much more than that somewhere around maybe 3 to 5 times the caliber diameter.
Some say the radius venturi design of his cartridges are one of the reason they have such a long freebore length, and the other being a much more influential reason for freebore, throat erosion. His cases and his loads found in a about every manual are higher than other comparable cartridges. The pressure spike is a lot different when you have a lot of freebore and are not placing the bullets near the lands. You will see an increase of velocity because of this, the bullet hasn't hit the lands and the pressure spike hasn't jumped much until your bullet contacts the lands.

Usually the freebore diameter is between .0005 (benchrest) and .002 (factory) bigger than the actual bullet. When using jacketed bullets the pressure behind the bullet will actually deform it a small amount and seal this gap. You wont lose any measurable difference of velocity where this gap is concerned. It happens in milliseconds and the length of the freebore, well you do the math and see if you can come up with any number that doesn't have 13 decimal places after the decimal.

Accuracy of rifles with long freebore lengths generally is not as good as ones with little or no freebore. Like most of the manuals say, (Weatherby rifles) "load the bullet so that it fits into your magazine this should net you the best accuracy" minus about .035 thou to keep your noses from being smashed.

One way around all of this if your looking for paper punching is using VLD style bullets and loading them so that only the boatail of the bullet protrudes into the case past the shoulder intersection.
This will also allow you to utilize a greater case capacity. Longer bullets will get you close to the lands and possibly even touch the lands if you're lucky.

Well good luck with your rifle and shooting.
Weatherby rifles need a long freebore to achieve listed velocities within acceptable pressure limits. Hot loads with bullets seated too close to the rifling will cause pressure spikes. Custom rifles in Weatherby calibers normally have much less freebore and lighter loads should be used.
If you intend on leaving the barrel/rifle as it is then my advice would be to try heavy bullets with a FLAT BASE. A long, flatbase bullet will likely still have the rear section of the bullet in the case while it engages the rifling under fire. This will aid bullet alignment at a critical time. Boattails or short/light bullets will be completely free of the case before engaging the rifling. This is certainly not going to enhance accuracy.
My 2 cents
I have shot a lot of weatherby freebores for over thirty years. I have not found them to be any more or less accurate than any other factory rifle. Some will shoot like a dream and some will not. Just because it has freebore doesn't mean it will not shoot accurately. Best advice is work up your best load for it and if it is not satisfactory then have it rebarreled. But don't give up just because it has freebore. I have and have seen many that shoot extremely well. On average the flat base bullets will be more accurate in the Weathery's but many shoot the boat tail design very well. You just have to see what your gun likes. I build quite a few rifles and do a lot of freebore chambers by request. I can't recall one I have done that would not hold 6" or so groups on the 650 yard target which is pretty good for a hunting rifle. On average they seem to get about 100-150 fps more velocity than the standard chamber. It has been well proven by the military as well as private studies that a freebore chamber on average will not be as accurate at long range as a standard chamber. There will be a slight amount of wobble in the bullet before it hits the lands and this wobble will show up again at long range in a circular pattern instead of a group. The military spend a lot of money to figure this out. For the best long range groups your bullet should touch the lands. But bottom line is if the rifle shoots then shoot it. About three years ago I built a personal hunting rifle in 300 ultra with a freebore chamber just to see what it would do. At the 650 yard target it shoots consistent 3 1/2" groups. I bust pop cans full of water off the target stand with it.
Hey thanks for the info.. I guess I won't get my underwear in a bunch until I have ran enough powder and bullets through the gun that I can't say my problems aren't due to operator error. I guess some flat base bullets might be the next course of action. Its gonne be horrible but somebodies gotta shoot these guns... Ha HA! Thanks again
By the way that was 80% and I can see that is true because with my factory Accumark in .30-378 and a 220 grain J40 Match Bullet I was getting one hole groups at 100 yards. My dad was anyway.
I called Weatherby and asked. I told them I was having problems with SMK's 200 grain in a 300 Wby Mag making anything less than a 3" group. I would get a couple touching, then a really nice "flyer" that helped open up groups. How nice. Had a severe problem with velocitys bouncing around also. They said to try flat bassed bullets, and there was no way possible that the problem could be associated with their free-bore. I also called Sierra, and they told me to try hotter loads. Alliant said it might be the primers, not the powder(R 25). I have tried flat bassed bullets and have shot some nice groups with them. But, Still trying with the SMK's! Possibly its that some companys have trouble changing, regardless if it might be the right thing to do. Us Americans are famous for that! (metric system for example) Good luck! littletoes.
I own a Sako 75 chambered in .300 Weatherby. It has the freebore, but apparently it's not a detriment to accuracy, because this is the most accurate rifle I own ( All my rifles are bedded, but other than that I don't own any custom jobs). I've tried various seating depths and have achieved the best accuracy with bullets seated deeper rather than shallower. When I seat bullets out as far as the magazine will allow, accuracy gets a little worse, but more importantly, I start noticing some signs of increased pressure when using maximum loads.

The statement regarding flat based bullets being more accurate in the .300 Wby seems to be true for my particular rifle. I recall one day shooting 6 three shot groups using the 180 grain Speer Grand Slam, which is a flat based bullet, atop some IMR 7828. Maybe I was just having a great day, but all six groups measured less than 1/2". The very first group made one hole that measured about .15" as I recall.

You're simply going to have to shoot that rifle with various loads to see if it's capable of good accuracy. But one things for sure, freebore does not automatically guarantee less accuracy.
Chris Mathews cogent reply to Light em ups query,I have gone and figured quite a bit about factory rifles and seating out to the lands,Oh the botheration,magazine too short,rounds made about 0001"out of true are way crooked once cycled thru the action,and hell and damnation a bullet sticking in a hot barrel at a crucial moment.If your chamber is true to the bore of your rifle and you work your fired brass to keep the bullet looking straight up the bore very good accuracy can be acheived even with "short"rounds.I do not think ammo made like this would be any use to a benchrest shooter or a long range hunter but it can be way good enough for most "hunting" situations.Bill Morris
I've had a Mark V Synthetic chambered in 30-378 for several years and have found that it's just as accurate as most of my production target rifles.

Seating a bullet to touch the lands is highly overrated unless you are a benchrest competitor.

Also it necessitates a lot of extra care in loading that is not needed for "regular" hunting or Long Range Hunting.

Ignore the freebore issue and concentrate on bullet and powder selection. Then if it won't shoot... Dump it....

Thanks for the info fellas. Just to update on my issue. 101.5 gr of reloader 25 & 180 gr. X bullet b.t. seem to have solved my problem. Its shooting under .5 M.O.A. now. I feel much better. Its gonna be a good fall.
free bore on Weatherby came to solve the problem of powder burning rate in the 50's and 60's there is "gap" in burning rate powder from the slowest available in rifle rate as 4831 powder and the very slow powders of 50 BMJ

to try to keep pressure level acceptable ( pressure increase when bullet force in grooves that name ingraving force in internal balistic and this is because when load are in the land pressure are highter tahn with same load of the land ) and get "Weatherby" velocity , deep free bore help to don't rise the pressure curve over safety level with powder burning rate fast ( for the use )

that because after Norma have develop the MRP powder ( specialy design for Weatherby case load ) and now most company have fill the gap between 4831 and 50 BMJ powder ( H1000 , IMR 7828 , RETUMBO , RL22 and RL25 , VITA N165 and N170 ... )

If you check other caliber European you can see that old calibers ( 7x64 6.5x55 .... ) have very deep throat for the same problem of powder ( design in the beginning of the 20° century ).
I have own a 6.5x57 Zoli rifle ( very inaccurate gun ) with a free bore so deep that a 155 SMK seat out doesn't sucess to touch the grooves .....and CIP chambering are not the best in accuracy ...

flat base are more accurate because they are longer on drive band ( cylindral part of the bullet ) and stay more longer in the neck before to reach ( at least ) the grooves .

so Weatherby rifle are not target rifle and this is not the way to try to compare Hunting rifle accuracy to match/target/BR rifle accuracy .

By tuning the load and good powder they can get good accuracy and far enought to take game .

Good shooting