Thread: .308 into .243?

Originally Posted by caberslash

Better results if you run it through a 7mm08 or 260 Rem die first.

Shoulder to neck angle on the 243 is pretty steep compared to the 308 so I would also anneal the brass first.

As mentioned, necks may come out a bit thick, but might be OK in a factory chamber.

Not worth the effort considering how plentiful 243 brass is.

Simple enough to check whether it's okay to chamber in your rifle . A comparison between the outside neck diameter of a fireformed case and a necked down case with a bullet seated will give you the answer . I'm sure others will be able to give you a safe difference in neck diameters to take into account any variations in brass thickness . It's difficult for me to say as my last 243 allowed for around 0.002" neck expansion using Lapua brass , which is pretty tight.

I've never had to neck down to 243 as brass has always been readily available, as stated by @caberslash . Given the current climate, things may well change .