Necking .308 down to .243

[Guy La Pourqe]

Good afternoon Gents,

I am getting a Ruger No.1 re-barrelled from 25-06 to .243... only because the .25 burned out, and I have lots of .308 brass and time to neck it down. The only problem is I have never done it before and have only seen it done on YouTube.

I ran the .308 through the .243 sizing die (with the expander removed) and slowly bumped the neck down to 6mm using once fired federal brass. It went through slick as could be... and all the measurements come out fine except the overall length. My info here has the min. measurement for .243 as being 2.035" My OAL after the operation, for five cases at random:

2.018
2.021
2.026
2.015
2.018

Do I need to fire form the brass, or is that too short to safely shoot? Can any of you gurus wade in and maybe help me out?

[Winger Ed.]

There only problem you might have-- which I doubt, is if the case is too short to firmly hold the bullet from dropping down inside it.
For example: look how short the grip range is for a .300Weatherby, and they do all right.

.30-06 and .270s are a little long-ish in the neck anyway, but I've always trimmed them a few thousandths shorter
than the 'trim to' length so I'll never have to trim them a second time.

Something everybody talks about that can be rather important
when going up or down on the mouth diameter is aneling it along the way somewhere.

[farmbif]

ive been resizing 30-06 into 35 whelen and the brass is always short but shoots no problem. I keep it sorted as to how many firings so that each lot is pretty much alike.

[country gent]

General rule of thumb is sizing up necks thin and cases get shorter, Sizing down necks thicken and cases get longer.

I have formed 308 down to 243 and its not hard use a good case lube and a heavy press. It forms down well. While it can be done in one pass I did it in 2 6.5 then 243 and shoulder, this extra step made very good cases. Necks may or may not need turned / reamed depending on how much the necks thicken. Mine required a light turning. to maintain neck clearance on a loaded round when chambered. One plus to this is you can turn for a fitted case in your rifle.

I would try a few cases unannealed and a few annealed and see what works for your brass and set up. If you dont need to anneal to form then anneal after cases are done.

Since between the shell holder and die body brass can only flow up you are compressing the same amount of brass into a smaller space and it thickens and lengthens.

Also work up to upper end loads carefully in these reformed cases as capacity may be slightly less.

Its a fun project and may increase accuracy if you go the fitted necks route. Here you need to know the chambers neck dia and turn to .001 under that for the loaded round. Reaming the necks is also acceptable to thin necks

[ebb]

What country gent said about necks , they can get too thick and cause big pressure problems. I necked down 308s to 260 and had issues but i think mine were too long not too thick.

[Mk42gunner]

Put the expander back in and try a few. It might just surprise you.

I firmly agree with not annealing until the case alterations are done.

Robert

[MostlyLeverGuns]

I've necked LC74 to .243 Win. Two steps - 7mm-08 then .243. I found loaded cases necks with .243 jacketed bullets to be under the SAAMI maximums for neck diameter of the loaded cartridges. Measure neck diameter over a seated bullet to check using quality dial caliper (not plastic) or micrometer to check. I measure the actual length of the chamber (using NOE neck diameter plug) to determine maximum cartridge case trim length. I trim to .005 under chamber length or to the shortest case in the lot (within reason). I have not had problems with shorter cases reducing accuracy, even as short as 2.010". Over length can be a problem, case squeezing bullet in transition from chamber neck to throat, causing high pressure, shorter cases don't do this. Sizing 308 to 243 gives the opportunity for a precise case headspace, as the sizing die can be set to just let the case chamber with a 'false' shoulder holding headspace when cases are first fired.

[skeettx]

I have never had any concerns with the tad bit shorter length.
You may or may not have to neck ream.
Let us know how it all turns out
Thanks
Mike

[243winxb]

New Barrel = New Brass. 308 to 243, waste of time.

No shortage of new brass. https://ammoseek.com/reloading/brass/243-winchester

[tankgunner59]

I have reformed .243 down to 22-250 with no problems. When I asked about it I received several posts that several folks who reformed 308 down to 22-250. The only other steps they used was to anneal the cases and reform to 250 Savage before reforming to 22-250. I trimmed my cases just under trim to length, about .002 under with no problems. They all fired just fine with no difficulties.

[dh2]

years ago I made 25-06 out of 30-06 I did end up with a case mouth thickness issue, for me the resolution was to get 270 Win Brass,
Remington after that made a factory round out of it.
with my line of thinking if you rave any 7mm-08 around it could save some trouble.

[BrassMagnet]

New Barrel = New Brass. 308 to 243, waste of time.

No shortage of new brass. https://ammoseek.com/reloading/brass/243-winchester

Neck turning is a royal pain! Buy it if it is available. Only form when not commercially available.

I formed 100 RP 308 to 243 and the necks were too thick to chamber. I had to neck turn. After neck turning 100 I said "Never Again!"
GI brass would be worse!

[1hole]

First, book "trim-to-length" isn't a specification, it's just a reasonable length to trim to, shorter cases are not a safety problem.

Second, buying new cases is fine if you don't enjoy learning new things; necking .308 to .243 is about as easy as it gets and it will make you a more knowlegable handloader.

The only safety issue with necking down is ending up with a neck so thick the bullets could be a jam fit and that's no good "fit" at all.

I'd suggest you get a box of new factory ammo along with your new rig and fire at least a few rounds to get some known safe necks. Fired cases expand to fit the chamber and spring back about a thousant. You can measure the fired neck diameters against a few dummy rounds of your newly formed necks; if you have a couple thou of clearance you're good to go IN THAT CHAMBER!

As a matter of personal belief, if reforming cases and turning necks is too much trouble why not just shoot factory ammo and delete all the bothersome details of reloading?

[Maven]

"Do I need to fire form the brass, or is that too short to safely shoot? Can any of you gurus wade in and maybe help me out?"

The short answer is you do not, Guy. However, you should anneal the neck shoulder area prior to loading. Btw, I've done this when I had surplus of .308Win. cases to reform into .243Win. After FL sizing with the expander ball in place, I reamed the necks in a Forster case trimmer. I then resized them a second time, expanded them with a Lyman M-die, annealed them, and loaded them with cast bullets. There was never a problem with accuracy or the slightly shorter necks gripping either CB's or jacketed bullets. Btw, I too have a Ruger #1 in .243Win. and it's a tack driver, especially with jacketed bullets.

[brstevns]

Neck turning is a royal pain! Buy it if it is available. Only form when not commercially available.

I formed 100 RP 308 to 243 and the necks were too thick to chamber. I had to neck turn. After neck turning 100 I said "Never Again!"
GI brass would be worse!

Makes me wonder if you ever made any 43 Spanish out of 300 win mag. brass! L.O.L.
Just had to get a dig in.

[243winxb]

SAAMI lists 2.025" as the minimum trim length for a 243 Winchester cartridge. Short necks may allow more throat erosion, same as 55 gr bullets.

For long barrel life, i like the bullets to contact the rifling before the bullet shank leaves the case mouth on FIRING. Single base powder will extend life also. IMR 4350, 4831.

[Maven]

+1 to the above!

[Guy La Pourqe]

Yeah... I found that the case necks thickened up, and that the wall thickness could be squashed back a bit by running it through the die with the expander ball in... but lord, it was tough crank on the press to do it. And I don't want to trim case necks. I went and bought some 243 brass and 'bit the boolit'.

I am in a bit of a pickle with my 45-75 bottleneck though. Brass is unobtanium, and apparently has to be formed from 50 Alaskan. I am absolutely stuck on that one... I will HAVE to form my own brass after my existing stocks for factory brass runs out. Will the same thing happen there, do you think?

[Guy La Pourqe]

Errr - and thanks for all the replies, guys! Have a blessed, Merry Christmas and a very Happy New Year!

[Texas by God]

Isn't the .50 Alaskan based on the .348 Win? Then can't .348 be formed to 45-75?
I have no idea, just throwing that out there- not that a lot of .348 brass is at the LGS, either.

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