Home Forums Reloading Big Game Rifles Necking down .308 brass to .243

Due to the shortage of reloading supplies available, I have decided that in lieu of .243 brass, I should just neck down some .308 brass, since I have about 400 just collecting dust.

What concerns me is that I presume the neck will be thicker, because of the necking down, and I have heard on this site that the necks should be reamed to the proper thickness. What tool is needed for this and where can I buy one ?

Also, the .308 brass has been fired four times. Should I anneal the brass first or wait until it has been reamed ?

Since you're going to move the brass a bit, and there is already some work hardening present, I'd anneal before sizing it down.

If you have a 7mm08 die hanging around it would be a good idea to use it as an intermediate step.

You need a way to measure the thickness of the brass, something like a tube micrometer. The tips of caliper jaws don't cut it.

If you do need to make it thinner, I suggest outside turning instead of inside reaming if concentricity is a concern. Inside reamers follow the hole that's already there while they're thinning the brass, and that does not assure the necks are trued up.

Neck turning tools are all over the internet. Sinclair, K&M, 21st Century, PMA tool, ...

Thank you Mathman. I appreciate your advice.

There is plenty of 243 brass available at all the internet suppliers. 308 to 243 is a long way to go. Much better choice to buy 243 brass.

In Canada there is zero supply and U.S. law prohibits me buying it in the U.S. or buying it on line in the U.S.

It's been done before




http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/8545289/Boxer--false_shoulder?

Moby1,

There is a way to measure the neck thickness with a standard caliper and come up with an answer to whether its too thick. After necking down, seat a .243 bullet, then measure the outside of the neck. If the diameter is more than .276", the necks need to be outside-turned or inside-reamed. Outside is better.

Ehhhh.... No it isn't... I've punched mountains of 338 WM down to 264 in one punch.

From my decades of shooting my 308, something is wrong if you have to anneal brass under 20 reloads.

Thanks Mule Deer. That really does make sense and is the way I will go.

If you were working with 4x fired brass, would you anneal before starting the neck down procedure ?

When I tried it this way even using the 7-08 die as an interim step, I caved in a few necks. Running them into the die first and annealing AFTER the sizing worked well for me.

Really a necessity.Same issue with crushing a few necks if you don't.

I've found this concern to be way overblown. There's really very little change even in sizing up or down two calibers. Never had to turn necks (which I despise!) in cases where the major change is the neck. The only time necessary is when you end up with a neck in the body of a parent case, as when going from '06 to 243.

Size one case down, then seat a bullet and measure the OD carefully. If you end up with a smaller OD at the neck than the OD of a fired case out of that chamber, you're fine. You can do that without a tubing mike.

You've got plenty of brass to experiment with, so could try one that's been annealed, and another that hasn't.

I have also found that heavily chamfering the outside of the case mouth can help with necking-down brass.

You might find a .260 die another worthwhile sizing step.

I've necked down a lot of 308 case's to 243 in one pass, always worked. And I don't anneal, ever. But if I had a 7-08 die I would neck to it first. I've done a lot of 30-06 to 25-06 also but always necked to 280 Rem and then down.

In the late 60's on the ranch I simply necked down TW 68's in a Lyman FL die, filled em full of 50 cents a pound 4831 and $2.25 80 gr. Speer rejects and shot em. No reaming or trimming but they did make bolt closing hard though! Shot the same 2 boxes of cases enough to burn the HVA barrel out, sometimes loading them 2-3 times a day, tough damn cases, lotsa ground squirrels then. DO NOT DO THIS NOW!-Muddy

A while back I sized a couple of Lapua 308 cases to 243 and seated bullets in them, and they did not chamber nicely at all in a factory Remington chamber.

Thinner WW brass may have worked just fine.

Moby1, try Wholesale Sports Winnipeg. Remington .243 $33.00 CAD + shipping.

I would like to thank everyone for their responses. I really do appreciate all the advice I have been given. It really does make me thankful for this great website that Rick provides.


Rooney

Thank you for the info on Wholesale Sports. I will give them a call.

the Langley store shows it in stock.

Mule Deer:

Thank you for this info. I just necked down one of my .308 brass to .243 in one pass with a Lee Collet die. With a sierra 80 grain bullet seated, the neck diameter is .274. I did however have to back up and use a small base die to get the cartridge to chamber, as the new .243 chamber is a much tighter fit than the old .308 chamber was. Now I just have to do a few more to ensure I get a consistent measure of less than .276.

Your help has been much appreciated.