270 wby seating

MT257

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Working on a load with IMR 4350 and 130 accubonds. Started with 68g at 3.25" and got the following group. Was thinking of playing with seating depth to see if it would tighten up. Is 0.02" too much at a time? For reference the circle is a quarter outline.
IMG_0516.jpeg
 
You said you started with a 68 gr load. This is the max load that Nosler lists. Did you try lower powder charges first? If not, you could have passed up a load with a tighter group.

Lots of variables to consider, seating depth is one. Different powder or even a different bullet.

With a freebore of .378" not sure how a tiny bit of seating depth will change things. Suppose you could go in both directions in .005" increments and see if there is a trend.
 
I agree with AZShooter. Weatherby has lots of freebore in their barrel/chamber by design. Messing with the seating depth might not do anything. Adjusting your powder charge could reveal the desired results of shrinking that group.
 
Seating depth made a big difference in my 257. I m at 3.415" oal which runs fine in my Rem 700 action. It too has same .378 freebore as the 270 WB does.

I ve heard lots of guys claim a flat base bullet is sometimes the trick on a long throat WB; don't know I was able to get BT, AB and TMK (Gamechanger) to all shoot good in mine at same 3.415-3.425 range.
 
Working on a load with IMR 4350 and 130 accubonds. Started with 68g at 3.25" and got the following group. Was thinking of playing with seating depth to see if it would tighten up. Is 0.02" too much at a time? For reference the circle is a quarter outline.
View attachment 602144
How close are you to the lands now? For instance, if you are .010-.020" from the lands with the group, I would start seating depth in .005 " increments and see what yields, then adjust accordingly.
 
How close are you to the lands now? For instance, if you are .010-.020" from the lands with the group, I would start seating depth in .005 " increments and see what yields, then adjust accordingly.
I've never tried chasing the lands with factory freebore on wby chamberings. Bullet would barely be in case.
 
I've never tried chasing the lands with factory freebore on wby chamberings. Bullet would barely be in case.
I am in no way implying that you should chase the lands. I prefer to measure CBTO over COAL because it is more accurate and provides a better reference point. I do not have a .270 WBY, but I have a .257 WBY, and yes, I can touch the lands. But I use heavier and longer bullets.

1726419341217.jpeg

(L-R: 110 SGK, 145 Black Hole, and 163 Chinchaga).
1726419550828.jpeg

These loaded with Retumbo/163 Chinchagas .015" off the lands, which is 2.790" CBTO or 3.415" COAL, similar to @MagnumManiac.
 
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I've never tried chasing the lands with factory freebore on wby chamberings. Bullet would barely be in case.
Not as bad as you would think.
The Weatherby Magnums have a long neck, especially when compared to cartridges like the 7mm Rem Mag.

If it were me, I'd try the 7828 powder that you have.
Fastest burn rate I'd use would be in the RL19/4831 range.

Weatherbys whole premise is speed.
The slower burn rate will also affect the recoil impulse. Giving more of a push, instead of a slam.
 
Not as bad as you would think.
The Weatherby Magnums have a long neck, especially when compared to cartridges like the 7mm Rem Mag.

If it were me, I'd try the 7828 powder that you have.
Fastest burn rate I'd use would be in the RL19/4831 range.

Weatherbys whole premise is speed.
The slower burn rate will also affect the recoil impulse. Giving more of a push, instead of a slam.
7828 I ran into a lot of pressure towards max load and no where near the grouping pictured above.
 
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