Thread: .308 into .243?

I have a heap of once fired hornady brass for my .308, how hard is it to make it into .243? Have heard it can be done relatively easy? Thanks

Fairly easy to do. Run it through the 243 Full lenght sized taking your time will yield good results.

A few things to look out for however is the increase in neck thickness and doughnuts that will sometimes form.

Size the 243 brass only until it will chamber in your rifle. Don't just give the brass total resize treatment which may create headspace problems. I used to resize military 7.62x51 brass for my 243 and 22-250 and it worked very well, helping to fill the overgenerous commercial chambers in my rifles.

Got a heap of federal brass.

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.

Have used 308 brass for years in 243, just resize until it will chamber. Just check like with all resizing that splits etc haven't occurred.

Anneal the neck after sizing. If you anneal before, there is a possibility for the neck to collapse. If you don't anneal afterwards, the necks will crack later. Polish the inside of your resizing die to make the resizing smoother. The whole process of resizing brass is fairly straight forward but it is best to do a small batch first to make sure you have every step sorted out.

Easy one to do, annealed or not. Use lube in correct amount and you will wonder if the cases are .243 in the first place...bugger all press arm resistance.

In common calibers it's technically possible, but as others have said unless you are badly short it's not worth it... Also consider the issue of mismatched head stamp, while it's unlikely to get an issue with remaking .308 into .243 in terms of chambering it is a possibility that you may strike issues with picking up a random .308 case and ending up with it stuck in a die or other whoopsies.

I saw a guy with a box of Win .308 ammo half of which was stamped 7mm08. He just hadn't checked and picked up 20 cases off the range and went home to roll up 20 more and never realized the difference.

Gonna flag this idea I think,have a bit of brass on the way. Thanks for the info anyways.

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 .

When I first got my 260 I didn’t have any brass for it so resized some 308 brass, worked fine but I did neck turn it just to make sure it wasn’t to thick.

Works perfectly, you just run it into a .243 die and it comes out .243. That's how Warren Page invented the 243 in the first place.

Theres no trick to it. You can anneal the cases afterwards or some may split in the neck after three firings. But annealing is not rocket science, I just use a candle.