Home Forums Reloading Big Game Rifles Making 308 Win from 243 Win?

Got a question maybe someone can help with. 308 Brass is VERY difficult to find right now and my wife bought me a 308 for Christmas and I have never used the cartridge so I don't have components for it. But, I do have a couple of hundred rounds of once fired Remington 243 brass that my late father shot up. Since the 243 is pretty much based on the 308 Win case I'm thinking of trying to open the 243 brass up. I can find a lot of info on line from going down from 308 to 243 but not the reverse.

All the dies I use are RCBS and I have 6.5x55 and 7MM Mag. I'm thinking I can increase the case mouth of the 243 brass in stages. I plan on taking the expander out of the 6.5 dies and the 7mm dies and use them on 308 dies and go from 6mm to 6.5 mm to 7mm to 30 cal putting lots of lube on the case mouth and then trimming if needed and fireforming the brass. In my mind this should work. My questions are:

Has anyone else tried something like this or am I looking at wasting my time and possibly wasting a lot of good 243 brass?

Would I be better off trying to trade someone 243 brass for 308 brass straight across? I am a little hesitant on this because I know for a fact the 243 brass has only been fired once since they were the factory 80 gr load that my late father used on coyotes but I wouldn't know the status of the 308 brass.

Any advice or input is greatly appreciated.

Good 308 brass is not that hard to find.

I've made 7-08 brass from .243 brass by running it into a .270 die just far enough to expand the neck. Sounds like with a 6.5 and a 7mm die, you're all set to make the conversion.

308 up from 243 is a neck stretcher, might lose a good percentage. Might have to outside neck turn to get rid of the "doughnut". This is good brass and would be easier to neck up.

https://www.grafs.com/retail/catalog/product/productId/73070

Have you tried finding it lately? New brass is out of stock everywhere. If I could simply buy 308 brass I wouldn't have made the post in the first place.

Have a nice day.

Thanks. Was hoping to use what is on hand but may end up going that route. I'm itching to shoot the rifle but hate paying what they ask for loaded ammo right now.

MAC
Yeah, times are tough, but just to help you not get bogged down.....

I would be willing to help you out with some 308 brass.
39 pcs of FC once fired nickle plated 308 brass and
31 pcs of Win IMI new 308 brass
At a reasonable price---no gouging.
PM me if interested.

I've gone the other way without any problem, forming 243 from 308.

It goes much easier if you anneal before forming.

I'd say just try a couple of pieces of 243 in your 308 die, and see what happens. It will probably be fine.

I could trade some military brass that has had the primer pockets swaged so that you can reload it. It’s fired once, cleaned sized etc.
I would trade for .243 brass. I may have some factory 308 brass too. But I don’t have much factory brass.