Hello:

Is it possible to neck down a 308 to a 243? If so, do I run a 308 case through a 243 die and then trim case length? Or, would I need to neck the 308 case neck down to 7mm, 6.5mm and then finally 6mm?

Thanks,
Ben

Try it, all it will cost is one or two cases. However, you will end up with thick necks, probably, and need to neck turn. Bummer and a lot of work. Buy your .243 brass, it is much more satisfying.

I used to do it all the time but did ruin a case or two. An intermediate die could be a big help. I used a 7-08 die and that guaranteed 100% success.

Quite a few reloaders size their .308Win. brass down to .243Win. Usually you can do it in one step, but as mentioned earlier, be aware of your neck thickness. I make it a point to shun the practice though since I shoot both calibers and have a fear of getting them mixed up. On a day when some cobwebs may remain it's not that dificult to look at the headstamp and grab the wrong cases. Best wishes.

Cal - Montreal

Here is some Lake City .308 brass necked down to .243, loaded with 40 gr IMR4895 and 100 gr [should be 67.5 kpsi], and then forced into the chamber with 100 pounds of force on the bolt handle [the necks were too thick].

pic of the brass



It is a good thing it was in a 98 Mauser and the only gas I felt came out the mag well [no bottom plate or follower were installed]. The gas bounced off the bench and came up and made slight breeze on my face.



I don't know why, but each case got harder to remove.

The last one had me pounding open, jumping on the bolt handle like a pogo stick, and the pounding out the case with a cleaning rod.

If you use a process of dies in steps and some simple annealing it is not only possible but mandatory to size .444 brass down to .243 to get a particular wildcat cartridge. As said earlier you will have to check the necks for thickening.
I make 6mm 30-30 brass all the time from either .375 win or 30-30 brass. I use a 7-30 Waters size die, then a .260 Rem and finally a modified .243 size die and it works out quite well. You may be able to skip..depends on the brass.