Making 243 from 308 questions

[Tripplebeards]

Well I found a couple of 308 range brass pieces the other day. I annealed them before trying to run them in my 243 FL die. I squished the two necks all the way down to the shoulders. So I failed. Should I have not annealed the cases first? I gave away all my other 308 brass so I’ll have to wait till I run into some again to experiment.

[Newboy]

i usually try to size in two steps, first to 7mm, then 6. Also, annealing makes them kind of "sticky", in my experience.


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[AntiqueSledMan]

Hello Tripplebeards,

I did some military brass once. I started with a 7mm-08 trim die, then went to a 243 trim die, worked them slowly through each die without annealing them. Finished with a 243 sizer and loaded them with no issues.

AntiqueSledMan.

[Winger Ed.]

I've never changed brass from one cal. to another, but reading a little about it-
when going from larger to smaller, guys talk of the neck getting thicker, and sometimes having to turn them on a lathe to thin it out
so there is enough room in the chamber for the neck to expand properly and release the boolit.

[M-Tecs]

Did a bunch of LC in the 80's. Stepped 7mm than 6mm. After fully sized annealed than had to neck turn. If I did it again today I would neck turn than anneal.

[BK7saum]

I would definitely run them through an intermediate die or two, 7mm08 possibly 260. that said, I'f you hadn't annealed first they may have sized down.

Also, make sure you remove the expander and entire decapping stem when necking down.

[Hannibal]

I've gone from .308 to .243 in one step with LC brass.

A good case lube is necessary. I made mine of petroleum jelly and lanolin. FLS in a .308 die, then FLS in your .243 die. Anneal last. And as others have said, the necks will be thicker. Make certain you have at least .002" neck clearance between your loaded rounds and chamber neck.

As an aside, the reason I necked down the cases to begin with was because I had a .243 that would.shoot. 3/4" @ 100 yds with neck sized brass, but only 1 1/2" with FLS brass. I wanted to experiment with minimal neck clearance. Finally figured out I was over sizing the brass in the FLS die. Oh, well. It was an interesting experience.

[Walks]

I haven't done that in years.

Brass is plentiful in all std calibers. So the only brass I've had to form from another case has been 7mmTCU. And that was going up, not down.

When I first got a .25-06 Whby Vanguard 45yrs ago, after Scope, mounts/rings, dies and 1 box of ammo and some Sierra 117gr Spitzer Boatails.
No money for Brass until the next month. And a lot of Oatmeal and Baloney sandwiches until I could afford to eat.

So I started to neck down some old mixed .30-06 brass. Rem & WW.
Greased up necks and sized down in a Lyman 310 for 7mmMauser, next a .270Win FL die. Last in the .25-06 FL die.
40 cases, didn't lose a single one. Got me through 6weeks before I could buy 6 boxes of Rem brass.

I think the reason I got through without losing a case was patience. And the step down sizing method I was able to use. And I used a finger to apply the old Lyman sizing lube. Not a single winkled neck. I used them for 3 loadings each. Didn't seem to have a neck thickness problem. Still got them somewhere out in my stash.

[Crusty Deary Ol'Coot]

Tripplebeards,

Your problem is the lube!

STP works great, but is the pits to clean from brass and the dies.

Imperial Sizing Wax will solve your problem.

One pass in and out of a .243 die and then, this is very important, turn the outside of the necks to not only true them up, but to assure that they are not overly thick after the forming.

Over thickness of the case neck can cause GREATLY increased pressures, to the point of destruction of the rifle if there is not enough room between the case neck and the chamber to allow for the bullet to be released without excess pressure build up.

I have formed .243 brass from both Military and commercial brass. NO PROBLEM, one pass in and out of the .243 die. Just keep your ducks in a row with the proper lube and turning the necks after forming.

Crusty Deary Ol'Coot

[kaiser]

I have sized .308 match brass to .243 with one pass without a problem by lubing the inside of the case neck with a brush. A word of caution is in order - be sure to “ream” the inside (or outside) of the necks after resizing and reduce your loads by a couple grains of powder, or you will experience some “hot” loads! Also, square up the case mouth for uniformity. I’ve found military brass an excellent source for reforming to.243, since its original design was for the abuses of the M60 machine gun. It usually has a longer service life than most popular brands in that caliber. Oh, be sure to take the crimp out of the primer pocket after that first resizing pass; a one time job.

[M-Tecs]

I have sized .308 match brass to .243 with one pass without a problem by lubing the inside of the case neck with a brush.

What does lubing the inside of the case neck do?

[toallmy]

I use LC brass to form 243 win brass , with one pass through the 243 full length sizing die . When I tried annealing before resizing I had a lot of smashed cases , so now I do my annealing after full length sizing with imperial wax .
A small part of the shoulder is pushed in to the case neck when forming so be careful ( DONUTS ) + they are a little short on OAL .

[cwlongshot]

100%. I will ONLY EVER re form cases using ISW!!

Good luck!

Tripplebeards,

Your problem is the lube!

STP works great, but is the pits to clean from brass and the dies.

Imperial Sizing Wax will solve your problem.

One pass in and out of a .243 die and then, this is very important, turn the outside of the necks to not only true them up, but to assure that they are not overly thick after the forming.

Over thickness of the case neck can cause GREATLY increased pressures, to the point of destruction of the rifle if there is not enough room between the case neck and the chamber to allow for the bullet to be released without excess pressure build up.

I have formed .243 brass from both Military and commercial brass. NO PROBLEM, one pass in and out of the .243 die. Just keep your ducks in a row with the proper lube and turning the necks after forming.

Crusty Deary Ol'Coot

[gnostic]

I make 243's all the time from LC 308 cases. Use a 243 trim die and neck reaming is a must. Neck ream after trim die and then full length size the case...

[Tripplebeards]

I just tried RCBS case lube and greased then pretty good. I have a feeling the annealing made them way too soft.

Turning 270 into 30-06 and 35 whelen is way easier.lol I don’t have any issues with up sizing it's the neck downsizing where I run into problems.

[cwlongshot]

Just buy or get IMPERIAL SIZING WAX!

Once you use it you will see.

CW

[kaiser]

M-tec, lubing the inside of the neck reduces the friction of the decapping pin when withdrawing the case from the sizing die. Another accessory sold by Hornady is a decapping pin with a carbide button incorporated on the stem that negates the need to use lube inside the neck. The idea is to reduce the caliber of the neck of the .308 brass without distorting its dimensions or cause the brass to thicken to the point it causes pressure problems! Going from .308 to .243 will thicken the neck when resizing the brass (going to a larger caliber like the .358 from .308 will not).
After the first firing, normal reloading procedures will work thereafter; however, your new military converted case will not hold as much powder as commercial brands (not a bad thing when it delivers the same velocity with less powder).

[MostlyLeverGuns]

I have reformed 308/7.62 Military to 243 many times. First I full length size/decap in a 308 die WITHOUT expanding the neck. I have used a 7-08 die as an intermediate step, again no neck expand, tho a 260 rem would probably work. I the run the case into my 243 SEATING die, then I size in my 243 full-length die. I have used Hornady Unique for this without problem. The inside of the neck should be lubed when(if) you are pulling the neck expander during the final sizing (Q-tip). Seat a bullet and measure neck diameter with a bullet seated. Smoke or use a Sharpie to blacken the neck and chamber in the rifle, the neck may or may not be too thick. Neck turning or neck reaming is sometimes needed but very often it is not. As said before case capacity will be different and max loads will need to be reworked. Annealing after final forming or after first firing will increase case life and give a more uniform bullet pull.

[GOPHER SLAYER]

I tried it but no matter what I did, the cases were shorter than factory .243 brass. A gentleman on this site sent me a die for the purpose of reszing 308 cases to .243. The cases were still too short. I was able to buy a large amount of .243 cases so I no longer need to worry about it. Those of us who have a .243 remember when the bras was not all that easy to find. Even worse is 6mm REM. I have one of those also.

[M-Tecs]

M-tec, lubing the inside of the neck reduces the friction of the decapping pin when withdrawing the case from the sizing die. Another accessory sold by Hornady is a decapping pin with a carbide button incorporated on the stem that negates the need to use lube inside the neck. The idea is to reduce the caliber of the neck of the .308 brass without distorting its dimensions or cause the brass to thicken to the point it causes pressure problems! Going from .308 to .243 will thicken the neck when resizing the brass (going to a larger caliber like the .358 from .308 will not).
After the first firing, normal reloading procedures will work thereafter; however, your new military converted case will not hold as much powder as commercial brands (not a bad thing when it delivers the same velocity with less powder).

Let me rephrase the question. What does lubing the inside of the neck do to help the OP's issue of "I squished the two necks all the way down to the shoulders."? The above is just basic reloading practice of bottle necked cases.