Need Some Help Sizing .257 STW

[TwoMore]

if you dont know your chamber length that would be hard to answer, that is a critical measurement , I make my own gauges but most of my rifles are tighter necks. You need to know what your chamber length is , then you will know if you need to trim or not. I would imagine that the chamber is the same as a 7 stw if i remember right my stw is 2.840 trim. but like I said thats a critical measurement
www.youtube.com/watch?v=JKnXJxaAw2U
edit : I re read your post and I think you are talking about the case neck junction. when i neck down it looks the same as yours and when I fire form they form to the chamber

 

[aldeerhunter]

Ok. Thanks. I will anneal, load a few rounds and see what goes.

The Remington 8mm brass must be softer than the Nosler. I have not been able to neck the Remington brass down without collapsing the brass.

 

[TwoMore]

I used to use the 8mm brass on my 7mm stw way back , it did well I necked it first to 30 cal then then the 7 , I just prepped up a batch of bertram 338 edge to 7mm ultra rogue , I necked it to 300 rum first then 7mm rum, it still looks a lil rough on the shoulder lol but it will form good. I have a new hydro forming die coming for that rifle, see how that does All the cartridges I neck down I use non busing dies on forming but I reload with bushings

 

[aldeerhunter]

Two more, I will try that with the 8mm cases. I have a full size 300 win mag die that will step the 8mm down a small amount. What 30 cal die do you use to step the 8mm down?

 

[TwoMore]

I used a 300 WM on the 8mm first

 

[aldeerhunter]

I used a 300 WM on the 8mm first

Great. I will give that a try. I still have about 40 pieces of 8mm Rem. brass that I would like to get some use out of.

Thanks for all of the replies. Now, maybe I can get to some load development.

 

[aldeerhunter]

Just wanted to say thanks again for the replies and advice. I got there following the direction given.

Let me start by saying I am not impressed with the Remington 8mm brass. Seems softer than the Nosler and is harder to deal with.

I had to start by using the 300 neck die. Then I used the .257 full size die which left a doughnut above the shoulder. So, I then used the 6.5 Hornady and then resized again with the full size die .257 die. The bottom photo is the virgin sized brass. The top is the first fired brass and one loaded round.

For anyone interested. I started with 73 grains of 7828 which averaged 3625fps. Once I form the last five roinds I will be ready to work up the load.