I’m wondering....Can I make .243 win cases out of .308 win cases I have ? If possible do I put them through the full sizer die or would I need a special forming die ?

Yes you can make 243 from most 308 cases....military cases don't work as easily for me as do commerical cases...the made 243 case will be slightly shorter than trim to length and sometimes you can just lube the 308 good and use a 243 die and get a case to fireform...a 7-08 die works for a inbetween size to make it easier....I annealed the 308 cases I used to make 243 and it seems to ruin less cases in the stepdown....I have HEARD of using a seating die without the stem for a sizing die by some inbetween the 308 and 243 resizing die? I use Imperial lube and just get the case to chamber in the 243 chamber and then fireform....hth..good luck and good shooting-loading!

The intermediate sizing with a 7mm-08 or .260 Rem die is an excellent recommendation. Depending on the brass, you also may have to neck turn or ream internally to bring the neck thickness down. If you don't, the pressures could be very high, IF the loads even fit into the chamber. Also, after forming, trimming, etc., weigh the cases to ensure they're close. Casual pick-up cases can come from very different lots weighing more than ten grains different, heaviest to lightest.
When I was much much younger, I used to make all sorts of cases from .308 and .30-06 match brass which I got for free. No problems as long as I was aware the brass was heavier than most commercial brass.

I would use a great deal of caution here. I remember reading the details of an incident where a 243 Win. rifle "blew up", ruining the rifle and injuring the shooter. It seems that the reloader used 308 Win brass to make his ammunition. One of the cases was thicker and the resizing compounded the problem and caused the neck tension to be much higher. When the cartridge was chambered, the chamber throat further increased the grip on the bullet. When the rifle fired, the bullet was held tightly and the pressure became greater than the action was capable of holding. The receiver and the first several inches of the barrel ruptured sending metal fragments and stock splinters into the shooter. I do not remember the severity of the injuries but I do remember the incident. I think this was in "Outdoor Life" or "field and Stream" back in the late 60's.

Why would you want/need to anyway. Good .243 brass is cheap, and available almost anywhere. Sell your extra .308 brass, and take the money and buy some new .243 brass.
And ditto duckhunter's post.....Grant.

No need to look for a boogyman under the bed but like most hobbies in life, a little common sense is needed. Fire a commericial .243 round in your rifle. When you resize your .308 case, seat a bullet in it and measure it acrost the neck. If it is smaller than the neck of your fired .243 case, you're good to go. If not, you need to turn the necks of your resized .308 cases which is a PITA. (don't ask me how I know)
My take is you should do a few so you can say, "I've done it" and spend $20.00 on a hundred proper .243 cases.

quote:

Originally posted by Oldmodel70:
Why would you want/need to anyway. Good .243 brass is cheap, and available almost anywhere.

In ICELAND, where the OP is at?

Size it down, verify the neck is not overly thick (IE needs to be reamed or turned) and go for it.

Winchester did.

If the .308 brass is new or only once fired (having relatively malleable necks), then it can usually be sized to .243 by simply running through the .243 FL sizer. DON'T over-lubricate the cases as you will find wrinkles or dents in the shoulders if you do. If you have a 7-08 or .260 Rem FL die to use as an intermediate step, that can be helpful, but not absolutely necessary.

Be sure to check the case length once reforming is completed. Trim, if necessary, and bevel the insides and outsides of the mouths.

Since most factory chambers are somewhat loose in the neck area, the reformed .308 may actually fit the chamber better due to its slightly thicker neck walls. Do exactly as Stillbeeman instructs to determine if you need to thin the neck walls. Inside neck reaming is easier than neck turning if you have the proper tool.

Another test is to load a conservative load in a resized .308 case and fire it. If a .243 bullet will not slip into the neck with only finger pressure, then you will need to thin the neck walls.

I use a lot of .308 brass for .243. Never any trouble and the only neck reaming I've had to do was with former military cases (which I no longer use.)

Thanks a lot guys ! I have some Lapua .308win cases that I have only used once and I think it is a shame to throw them away. I’ll borrow a full sizer in 7-08 from a friend and use it as intermediate step and then run through the .243 sizer.