FREEBORE ON WEATHERBYS

[light em up]

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.

[chris matthews]

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.

[Varmint Hunter]

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
VH

[Long Time Long Ranger]

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.

[light em up]

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 [img]images/icons/grin.gif[/img]

[Nighthawk]

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.