.257 WBY - 120 Grain Partitions

[TBASTIAN]

After working out some final loads for the 100 grain TTSX and 115 grain TSX in my Mark V, I'm planning to work with the 120 grain Partition again. I'd like for this to be my go-to bullet, but haven't been able to find the right load yet.

Anyone know the OAL that Nosler uses in their ammunition? Also, any pet loads, primers used, and OALs would be much appreciated. Thanks.

 

[Mountain Goat]

I've only loaded for one 257WBY, but it loved the 120gr NPT with IMR7828ssc and a WLRM primer. I don't have my data with me, but I recall OAL to be around 3.20". That is one of the coolest Weatherby cartridges, IMHO.

 

[JD338]

I would guess that Nosler loads to the SAAMI spec. That would be a good starting point.
Do you know how much free bore your rifle has?

JD338

 

[TBASTIAN]

I don't have the tool to measure that JD.

 

[JD338]

take a fired case and slightly deform the case mouth so that it will hold a 120 gr PT. Insert the bullet into the case and chamber it. The bullet will touch the lands and get pushed further into the case.
Carefully remove the case and meaure the COL. Do this 3-4 time to ensure you have an accurate reading. This measurement is the COL to the lands with the 120 gr PT. Back it off .015" and start there for accuracy. Make sure that this COL does not exceed thw magazine. If it does, that your MAX COL will be the magazine.

Hope this helps.

JD338

 

[TBASTIAN]

Great tip. Thanks, JD.

 

[JD338]

Glad to help buddy.
Let us know what your findings are.

JD338

 

[bbearhntr]

TBASTIAN, I played around a little with 120g PT in my .257 bee and was having a real tuff time finding any accuracy until i seated my bullets as close to factory OAL as I could get. 3.160" I believe all weatherby's really like to jump to the lands! I didn't spend nearly enough time on this gun and bullet combo but will give it more attention in the coming months. I never pushed it hard but was finding 3/4" accuracy with 70g of RL25 and Fed 215M primers. I am going to try IMR7828 along with RL22 to see what I can sqeeze out of this gun. I look forward to reading your results!

 

[bob_dobalina]

TBASTIAN, I played around a little with 120g PT in my .257 bee and was having a real tuff time finding any accuracy until i seated my bullets as close to factory OAL as I could get. 3.160" I believe all weatherby's really like to jump to the lands!

I've found the same with my 300 wby

 

[Alaska]

IMR 7828 @ 69.5
Fed 215M
120gr Nosler P
COAL: 3.250"
Vel with 26" Barrel
3375 FPS

100gr Nosler P
IMR 7828 @ 73.0
COAL: 3.160"
Vel: 3655 FPS

For todays WBY Freebore
.224 Weatherby Magnum is .162
.240 Weatherby Magnum is .169
.257 Weatherby Magnum is .378
.270 Weatherby Magnum is .378
7MM Weatherby Magnum is .378
.300 Weatherby Magnum is .361
.340 Weatherby Magnum is .373
.375 Weatherby Magnum is .373
.378 Weatherby Magnum is .756
.416 Weatherby Magnum is .239

 

[TBASTIAN]

Thanks, Jeff.

Loaded some 120 grain Partitions over 64.0 and 65.0 grains of RL 22.

Also, loaded some 117 grain BTSP Interlocks over 68.0 and 69.0 grains of RL 25. We'll see if there's any promise shortly.