[Navy_Guns]

"The Handloader's Manual of Cartridge Conversions" says you can form .243 cases from .270 cases, and in theory the .308 Winchester should work, too. I've never formed cases before - what does it take? I figure some Imperial sizing wax, a .243 die, case trimmer and an outside neck turning tool?

Can someone please walk me through it?

[Walkalong]

It is real straight forward. Run them through your .243 sizer using the Imperial. Easy enough. You may not need to ream or turn cases. You will just have to take some measurements when you are done.

The .243 is a necked down .308.

[Doug b]

I remember reading a long time back there are issues necking down 7.62 NATO to .243 win.

[cdrt]

You will probably have to inside neck turn them. This came up years ago when the .243 first came out and guys were necking down military brass. Just mike it after you re-size to make sure of the inside diameter. They had pressure issues with the military brass.

I remember one guy who tried this; ended up with a lot of split cases and definite over pressure loads. Luckily, it did not hurt the rifle.

[Doug b]

Cdrt yep this article dealt with a separated case between the neck and shoulder, the neck remained in the chamber and in a hurried follow up shot the Rem.M 760 was able to chamber and lock up and fire.

[Navy_Guns]

Clear this up for me:

As you run the .243 die down on the 7.62 case, the expander ball will go in the oversize case mouth before the case is necked down. Then the die will resize the case neck on the outside. Then when you lower the ram, the expander ball will open up the case mouth/neck to the proper ID (or close to it). I would figure that with the extra wall thickness in the case neck, the OD would end up slightly too big, and the ID may end up to small as well due to the higher elastic/lower plastic deformation when the expander is pulled through.

Which is it, do you need outside turning or inside reaming of the formed case? If the ID is too small, seating the bullet could push back the shoulder, right? If the OD is too big, it may not chamber or could increase the pressures do a dangerous level...

[Doug b]

My clarification 7.62 Nato is not 308 Win. it can be made .243 Win. but is it worth it?

[243winxb]

Navy Guns, a donut MAY form at the neck shoulder junction on the inside of the case neck. This is a ring of extra thick wall diameter metal that comes from the shoulder area. It is reamed out by inside neck reaming. The donut will sometime return ever after reaming. You can tell if its there by taking a fired case and seeing if a bullet will drop into the case the full length . The neck may also need outside neck turning. Loaded neck diameter .276" maximum. The brass over all length will be shorter then normal, no trimming for a while, but will increase throat erosion of the barrel. The erosion happens anytime the bullet does not seal the bore before the base of the bullet leaves the case. You understand the basics from what you said above.

[ranger335v]

Much like the death of Mark Twain, the fears of dangerously thick necks from necking down are greatly exagerated, usually by people who have not done it. Obviously you have to measure the necks of loaded rounds to insure they are not oversize but it is VERY infrequent when making .243 from .308/7.62. Necking down adds little to the final thickness and our factory chambers are usually much to loose for that to matter at all.

However, if you use much longer brass as a donor, such as .270 or 30-06, you WILL have thick necks that need outside turning. If so, don't bother to use an inside reamer, it will only make the necks thinner without any reguard to concentricity, turn the outside to a consistant thickness. And using a file trim die makes cutting longer cases to the right length fast and easy.

I make a lot of my small cases from bulk .30-06 (making .22-250, .243, 6 mm International, 257 R, .308, etc.) specifically so I CAN turn the necks to be concentric and snug fitting in my chambers.

If all someone wants to do is blow holes in targets or game it's hardly "worth it" to form such cases. But, if you want those holes to be close together, it surely can be worth it to make custom fitted brass for loose factory chambers.

In your case (pun) stepping down .308 stuff in a single step with only a .243 FL die works but it's easier to have an intermediate step. Using either a 7-08 or .260 FL die, or both, (no expander buttons are needed) to step them down gently works great.

Much of the GI brass (7.62) is slightly thicker in the walls so you cannot willy-nilly mix the GI cases with .243 cases without care. As with any other component change, your loads need to be developed with the new cases as a base.

Using the expander button in the .243 FL die takes pretty good care of the dreaded doughnut because it expands the extra thickness to the outside before neck turning, if that's needed at all, so it's gone.

It is a good thing to properly anneal the finished necks to prevent premature splitting.

[USSR]

it can be made .243 Win. but is it worth it?

+1. Since .243 Win brass is readily available, sell the .308 brass and buy some .243 brass.

Don

[243winxb]

http://www.huntingtons.com/dies_caseform.html Link to case forming dies for other hard to find brass or wildcats. If you can buy the brass over the counter, buy it.

[MMCSRET]

In 1985 while passing thru Guam on our way back to the States we were given a 55 gal. drum of Mil. 7.62 brass. We formed it to lots of different cal. We found that reaming 243 and then sizing the neck a gain worked very well. It can be necked up to 7.65 and used in 7.65x53 as the case is only 2mm short and will grow on firing.