Load Development Methodology - .257 WSM

[JMRhino]

Hi all.

I am hoping to leverage someone's knowledge and experience to help advance my load development methodology for a non-SAAMI wildcat cartridge. Specifically, this is for a Kimber 8400 with a 23" Pac-Nor 1/10 barrel chambered in 257 WSM (not to be confused with 25 WSSM). I had this built back in approximately 2005.

I have achieved fair results with RL22, IMR 4831 and most recently MagPro with some TTSX monos. I don't believe that I have reached the ceiling yet for any of the loads. I used to use some software titled "Load from a Disc" but it doesn't appear to be supported anymore at least for the platforms that I use. Absent software, I compared other similar type cartridges in terms volume, bore diameter, and projectile BCs to get me in the ballpark. Is it reasonable to compare to a cartridge like 257 Weatherby Mag and adjust for case capacity to create a starting load?
E.G. - If the Weatherby case has 12% more capacity, can I reduce the theoretical starting load for the 257 WSM by 12% and be in the same starting range? Is Ramshot Hunter or RL19 is too fast? My supply of RL22 is nearing its end...

Guy - I believe that I read your article and saw a previous post about you trying Hunter with a 244 REM. That seems to be a relatively similar comparison in terms of high powder volume to bore size but not necessarily charge weights. Were you happy with the results?

Ultimately, I am pleased with what I have accomplished so far but it's been painfully slow and many trips to the range. I am curious if there is a more efficient way of doing this other than buying more software. If not, that's ok too. I think that my current loads behave more like a 25-06 on steroids which ain't bad. I have only killed 2 whitetails at approximately 150 yards with this rifle and 115gn NOS BT and the terminal performance was excellent; however, I don't think that distance is a true test of its capability.

Since I was operating in uncharted waters, I believe that I stayed conservative in all of the loads and didn't experience significant pressure signs other than primers starting to flatten out a little on one of the loads. I don't remember exactly which one without my notes in front of me.

Example Loads/Velocities:
1. Norma Brass
58 gns RL22
NOS 115 BT and NOS 110 AB
AVE Velocity - 3200 FPS
Average group (3 shot) - 1"

2. 60 gns IMR 4831
80gn Barnes TTSX
AVE Velocity - 3679 FPS
Average group (3 shot) - .9"

3. 63 gns MagPro
100gn Barnes TTSX
AVE Velocity - 3300 FPS (seems a little slow)
Average group (3 shot) - .9"

Sorry for the lengthy and tedious post and please humor my glamour shot. Have a good weekend and stay safe.

Respectfully,
JMRhino

 

[wvbuckbuster]

No experience with this but want to say that is a nice-looking rifle.

 

[salmonchaser]

One of the beautiful things about hand loading, rifles and particularly wildcats, there is a little bit of witchcraft involved. My 338 Jarrett has slightly more case capacity than the 340 Bee. Should be able to exceed max loads for the 340. I can but not by the same percentage the Jarrett exceeds the bee in case capacity. I still get better velocity than the same load in a Bee.
When I want to try a new powder in the Jarrett I start at the low end of 340 bee without issue. How do your existing loads compare to 257 B data?

 

[JMRhino]

No experience with this but want to say that is a nice-looking rifle.

Thanks. It has a good looking stock. It started out as a Kimber 8400 300 WSM with French walnut that I won in a local big buck contest. I already had a 300 WSM so I modified it to the 257. I also have a Kimber 8400 in 270 WSM of the same era that has tiger stripes in the “classic” walnut stock. Great stock trigger too. That one is a shooter with factory fed premium w/ 130gn NOS BT. I hand load for it but it’s not really necessary.

 

[JMRhino]

One of the beautiful things about hand loading, rifles and particularly wildcats, there is a little bit of witchcraft involved. My 338 Jarrett has slightly more case capacity than the 340 Bee. Should be able to exceed max loads for the 340. I can but not by the same percentage the Jarrett exceeds the bee in case capacity. I still get better velocity than the same load in a Bee.
When I want to try a new powder in the Jarrett I start at the low end of 340 bee without issue. How do your existing loads compare to 257 B data?

257 B? I’m not tracking. So sorry.

 

[salmonchaser]

257 B? I’m not tracking. So sorry.

257 WeTherby

 

[JMRhino]

Ah. They’re close but maybe 100 fps slower depending on the load. The 115 NOS BT with RL22 were about identical at 3200fps but I feel like the 100gn TTSX should be faster.

 

[JMRhino]

I put a new Trigger Tech trigger in my Kimber 8400 chambered in 257 WSM so I thought this was good opportunity to gather some data. The first group was high after replacing the trigger, so I merely brought it down a few inches. I'm content with the velocities and ES/SD. The 80gn TTSX load was part of the second half of the target not shown here. I think that I have more capacity and velocity to be found but I think that I'll pause here as I am close to the whitetail season. Just thought I'd share...

 

[Blkram]

Looks like you have a winning combination for whitetails out as far as you are comfortable shooting.
Best of luck!

 

[RL338]

I run those 100gr TTSX in the mid 3500’s out of my 257 Wby , death ray on deer.
You’ll like that bullet on your whitetails.

 

[filmjunkie4ever]

With the advent of the 25 Creedmoor (1-7” twist, 130-135 grain high bc bullets, etc) it would not surprise me to see a .257 PRC or .257 WSM type cartridge along the same vein. Looks like you’re already ahead of the curve. That Kimber is beautiful.

Wildcats in my experience are a law unto themselves so to speak. Basic rules apply but pressures, powder charges, accuracy nodes, brass life etc. will leave you scratching your head a lot of the time.

I had a .257 Norma-Weatherby Magnum for a few years that was nothing short of a Pain in the @$$. In short, there was a 15-step process to trim and form full length .308 Norma Magnum brass down to a shorter version of the .257 Weatherby Mag. As far as I can tell, I had the only one to ever exist.

The rifle was gorgeous, built in the 1950’s on a Springfield 1903 action, Bliss Titus barrel, Canjar set trigger, etc. But after all the money invested it was basically a hot loaded .25-06 with no easily modified commercial cases to form from. And it shot 1.25-1.5” groups on its best days, if I held my mouth just right.

I eventually had it rechambered to .257 Weatherby Magnum and then traded it to a cousin for something else I wanted more.

 

[JMRhino]

I run those 100gr TTSX in the mid 3500’s out of my 257 Wby , death ray on deer.
You’ll like that bullet on your whitetails.

Yep. I think it's a good combo and I may be able to get another 100FPS put of mine. I progressed slowly in development as there isn't much data on the wildcat. I found decent numbers all around and then stopped. I shot a few whitetails with it years back from 150-200 yds with 115 NOS BTs with great terminal performance. I am new to the coppers.

 

[salmonchaser]

The more I play with the quarter bores, the more I like them. Bonded and mono bullets do nothing but make them better options for a wide range of hunting endeavors.

 

[JMRhino]

With the advent of the 25 Creedmoor (1-7” twist, 130-135 grain high bc bullets, etc) it would not surprise me to see a .257 PRC or .257 WSM type cartridge along the same vein. Looks like you’re already ahead of the curve. That Kimber is beautiful.

Wildcats in my experience are a law unto themselves so to speak. Basic rules apply but pressures, powder charges, accuracy nodes, brass life etc. will leave you scratching your head a lot of the time.

I had a .257 Norma-Weatherby Magnum for a few years that was nothing short of a Pain in the @$$. In short, there was a 15-step process to trim and form full length .308 Norma Magnum brass down to a shorter version of the .257 Weatherby Mag. As far as I can tell, I had the only one to ever exist.

The rifle was gorgeous, built in the 1950’s on a Springfield 1903 action, Bliss Titus barrel, Canjar set trigger, etc. But after all the money invested it was basically a hot loaded .25-06 with no easily modified commercial cases to form from. And it shot 1.25-1.5” groups on its best days, if I held my mouth just right.

I eventually had it rechambered to .257 Weatherby Magnum and then traded it to a cousin for something else I wanted more.

Sounds like an interesting cartridge. My 257 WSM is my only "wildcat," but it has been pretty predictable so far, however, I also don't push the limits too hard. My barrel for it was made and chambered by PacNor and I have been very happy with it but when made back in about 2005 it was throated pretty tight. I originally used RL-22 but since I am running low with it, I have tried to expand my options and have tested MagPro and IMR-4831. Thinking about tinkering with Magnum, Grand and Hunter in the Ramshot brand or some RL-23? I am in no rush since I have enough loaded to shoot deer for years in this and other cartridges. Cheers.

 

[xphunter]

H-1000 used to be my go to powder for the 6.5 WSM (Leopard) with 130's