300 WSM brass to 270 WSM

I size down 7 RM to .264 WM all the time. Not an issue. You do want to use a good sizing lubricant though. I would adjust the die so part of the neck is sized down, and then incrementally size down further and further, while trying the cartridge in your gun as you go. You want to just size it enough that the case just fits, and not over size it. You may see a bit of a false shoulder on the neck, but that is OK. You want the case to have close to zero headspace when you fire form it to your chamber. If you have a standard factory chamber in your gun you should not have to neck turn.
 
b72471 said:
You can do this BUT it's easier to buy 270WSM brass 1X. The quest on turning necks will be a feel when chambering the round, should be no resistance on the neck.
enjoy
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I would rather neck down cases, than pay for cases that may have been fired in an oversized chamber, and as a result might not chamber in my rifle after being run through a standard FL die. As for neck clearance, I want at least a couple of thousands of clearance, not just no resistance chambering a loaded round.
 
Measure the necks of some .270 WSM's that have been fired in your gun. Add 0.001" to estimate the diameter of the neck in your gun. Then compare that number to the size of a loaded round of the resized 300 WSM brass. That will give you an approximation of the clearance you have in the neck. Factory chambers are generally oversized, and having a little extra brass in the neck is not all bad, as long as you have sufficient clearance.
 
tigrr said:
Sizing a .308 down to a .277 will need a neck turning. Unless you want deformed necks when the .277 bullet gets pressed in.
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I often neck down more than that without neck turning, and I have had no issue seating bullets. If the necks are deforming, you either are not chamfering the case mouths enough, or you have too much neck tension.
 
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Tick said:
Can this be done with a single 270 WSM die or do I need a two step process, and will I need to turn the case necks after resizing?
Thanks Tick
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Personally, I would turn before starting and go in 2 steps... 7mm, then 270. I really don't want brass to form at the base causing donuts and the few seconds it takes to thin the neck before starting is miles better then trying to resolve donut problems.

But why not just buy 270 WSM brass? Assume you dont need buckets of the stuff?

Jerry
 
Did a quick calculation. Brass thickness in the neck will increase by about 0.0015". If the 300 WSM brass thickness is 0.015, it will increase to about 0.0165". Most factory chamber necks are going to like this more than they dislike it. But, the proof is in the pudding. Size a couple, seat bullets, and see what you get...
 
stubblejumper said:
I would rather neck down cases, than pay for cases that may have been fired in an oversized chamber, and as a result might not chamber in my rifle after being run through a standard FL die. As for neck clearance, I want at least a couple of thousands of clearance, not just no resistance chambering a loaded round.
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X2 I agree 100% if i do resize it is with new cases not once fired.
 
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