making 7-300WSM brass. neck turn and trim before or after neck sizing?

[prairieguy]

Gents,

I'm off on a wildcat adventure and looking for some advice.

I want to neck down a batch of Winchester 300WSM brass to use in a 7-300WSM.

Do I trim to length and neck turn before or after I neck down the brass?

Any advice is much appreciated.

 

[Steve Blair]

After

 

[TonyR]

I've made them out of both the 270 necked up and the 300 necked down. In both cases, I necked sized them up or down first then trimmed to length then turned them. The 270 WSM is the easiest place to start and can be done in one step with your neck turning expander. If you start with the 300WSM, make sure your last step before you use the expander for the neck turner is a non-bushing full length sizing die because you want the neck sized all the way to the junction with the shoulder. Bushing type dies leave a little gap at the base of the neck. It also helps if you have some sort of inside neck reamer like a K&M carbide mandrel on the turner because this neck resizing process seems to create donuts that make it hard to get the necks onto the neck turning tool otherwise.

 

[prairieguy]

Thanks for all the information so far.

Couple more questions though.

I intended to use 300wsm brass because I have a pile here on hand and didn't want to spend the extra money to buy .270 WSM brass. Maybe this isn't the best idea.

The reamer has a .315 neck so I want the finished loaded rounds to be .312. I don't have to take much off the case necks, I just wanted to clean them up and make them uniform.

How do I full length size with a non neck bushing die? The shoulder on 7 WSM cases is farther forward on the case so the 7 WSM FL sizer will not reach the shoulder and a 300wsm die won't work either. Is ther any alternative to buying a 7 WSM die and cutting/grinding it down to fit?

Do I still need to do this step if I size up from .270 WSM brass or can I just expand it on a mandrel then run it through a Full length bushing die then move on to trimming and turning?

 

[TonyR]

You can convert 7mmWSM dies to 7/300 by shortening the 7mmWSM die by about 0.040 inches. With the 270WSM, you can expand then turn without resizing but you should trim before turning because most neckturners index off the case mouth so the necks should be the same length or you may cut the shoulder inconsistently. At some point, you will need dies to reload with and shortening the 7mmWSM dies is the easiest way to get them. I bought the Forster set with the micrometer seater and had the sliding sleeve shorted by 0.040 inches also. You will have to check the neck tension but I think a 0.312 loaded neck will be just about right for the Forster F/L sizer without using an expander ball. I use a 0.310 loaded neck in a 0.314 chamber neck and the neck tension is a too little loose. 0.311 loaded neck works better and I think 0.312 would also be fine.