Making 243 from 308 questions

[country gent]

I have only formed a little 308-243 0ver the years. My one 243 is a tight necked chamber with .267 neck so all brass for it must be turned. Several things need to be watched when doing this, 1) neck wall concentricity. resizing can cause uneven wall thickness. 2) neck wall thickness can thicken sizing down making rounds tight to chamber and no release room when fired. Sizing down thickens the neck sizing up thins the neck. 3) Depending on shoulder angles neck dias and body tapers of the 2 cases brass can shorten or lengthen.

There is a set amount of brass in the parent case resizing this the brass flows to make what is formed with that brass. cases can lengthen since the brass can only move forward, sides and base are fixed sizes.
Necks can be addressed by reaming or turning. reaming thins the neck to a safe thickness but dosnt correct the wall thickness variatiions. Neck turning with a special tool and mandrel corrects the wall thickness and wall thickness variations to a very close wall thickness. Neck turning needs to be done carefully to avoid the dreaded doughnut at the shoulder neck junction. Some of my best wildcat cases were both neck reamed and turned. Necks were reamed in a die by hand .002 small sized on the turned mandrill and neck turned to size. This gave a neck wall thickness needed and a variation of .0002 on thickness.

[uscra112]

Don't anneal first. I did .308 to .243 many years ago in one pass, using RCBS lube. Have never used the Imperial wax, even for much more drastic reforming. Just a dumb swamp yankee who doesn't know better I guess.

Remove the expander ball and stem from the .243 die. Expand to .242 ID using a Lyman M die. Then turn the neck OD to fit your chamber and to true up the neck wall thickness.

[15meter]

I'll contradict all the "must" neck turners. It's rifle specific, I've got a Remington 700 that shoots better with Hornady 308 brass single pass re-formed with a standard Redding .243 sizer. I've been doing this since the rifle was new 3000+ rounds ago with zero pressure signs.

Try it, then measure to be sure that it is not too tight before neck turning.

I use Imperial as lube and anneal after forming. Anneal before and it is too soft and collapses as the OP noted. I've annealed half way through a conversion if it takes multiple steps but never before I started.

I used 308 converted brass in a match Saturday with the rifle shooting right about a minute of angle back to 300 yards and right now I'm loading about .220 long to get near the rifling because it's getting time for a new barrel.

I just have to decide .243 again or something different? Decisions, decisions.

[country gent]

15 meter, I will agree that some rifles will be okay with reformed neck thickness but they are fewer than most think. Several variables have a bearing here, 1 the original brass wall thickness. The forming operation itself may affect this. Hardness or make up of the brass I sized some Lapua 308 down ( just a few cases to see). It was borderline in the chamber of my AR10s chamber neck. Thickness uniformity wasn't bad but also not what neck turned would be. A loght clean up and removing .0005-.0007 on dia would make a 80% clean up and better neck wall. On thicker brass like some military it may require heavy turning.
I had a rem 700 bdl varmint that would accept Winchester reformed brass fine some Remington brass but the mil surplus required turning. Tis I did same as for my tight necks and fitted it to the rifles chamber with .0005-.0007 loaded dia clearance, This ammo shot very well.

[MostlyLeverGuns]

Case necks of 308 resized to 243 are thicker than most factory 243, though they normally are not 'too thick'. Lubing the interior case neck allows the case neck to slide over the expander button more easily, reducing stretching and making the process easier. It should also reduce stress on the resized neck. I use a Q-tip to wipe lube out of the case necks. I now use a Redding bushing die for most resizing, avoiding the pulling the neck expander through the case neck. An 'M' die is used for neck expansion most of the time, size depending on bullet diameter. Hearing the squeak and feeling the friction of a dry case neck over an expander ball is not pleasant to me. I also have used the Lee collet die then an 'M' die that also works very well.

[tankgunner59]

I'm with the majority here. I don't have a 243 but I have formed 22-250 from 243, it's not as big a reduction but I think it'll work for you. Also after asking here about reforming I took their advise and got a K&M neck turning set up and I turn the necks after I trim, chamfer and beburr. Lastly I anneal the brass. You're asking the right people, I got my info about reforming here, followed it and have loaded and shot them with no problems. These folks know what they are talking about, for sure.

[kaiser]

M-tec- You are correct that inside neck lube does nothing to help size a .308 case to .243. I've not ever had the problem of "squishing" the necks on Military match brass (I've never tried it with regular commercial brass. Sorry for the confusion)

[Mr_Sheesh]

About the first case forming I ever did, I think I was around 10 years old; Formed about 3000 rounds. Had a very good case lube (purple grease, I WISH I knew what it was; Dad was a Chemical Engineer so he found about the best available then.) Annealed; Sized down to 25-308; Neck reamed; then sized on down to .243 & reloaded. Worked quite well

[dogmower]

Generally, it's easier to neck UP than DOWN. brass has to go somewhere and there's more brass in a .308 neck than a .243, so the neck gets thicker when you go down in size.

[Mr_Sheesh]

You do want to lube the inside of the case neck for necking up, as an aside. (And clean the lube completely afterwards, neck tension is bad for humans but good for loaded ammo )

As a youngun it was very nice shooting and reloading brass I'd first formed, knowing how well it worked

[Wayne Smith]

About the first case forming I ever did, I think I was around 10 years old; Formed about 3000 rounds. Had a very good case lube (purple grease, I WISH I knew what it was; Dad was a Chemical Engineer so he found about the best available then.) Annealed; Sized down to 25-308; Neck reamed; then sized on down to .243 & reloaded. Worked quite well

The lube I use is red, not purple. It is CFL-56 Case Forming Lube. It says it contains Amine Phosphate compounds.

The mistake the OP made was when he annealed. I form the neck of my 25Krag in two steps and then anneal. When I have annealed first I get the same shoulder collapse he described. Yes, I remove the expander button from all the dies I use and expand with a Lyman M die.

[Drm50]

When I started out with 243 I had no 243 Brass. I had Military 7.62 by the bucket. I formed all my brass from military and as someone has already posted it always required neck reaming. There was once an article in NRA magazine in 70s about forming 243 out of Mil 7.62 NATO. There was a picture of a pre64 Win M70 in pieces on a blanket. That got my attention even though I had be doing it for at least 10yrs. I only used Match brass because that's all I had. I new a leak from Camp Perry who gave me brass. I didn't do anything other than run it in 243 sizing die, neck ream and FL it again. I still have that rifle, built on 98 my uncle got in WW2 with Douglas heavy barrel. Thousands of rds made of 7.62 and still going strong. It is my main groundhog gun. At 12lbs that's all it's good for.

[Gaseous Maximus]

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.

Around 35 yrs ago I did several hundred LCs . ran them thru a 08 fl die and then thru a 7mm neck sizer which I had made,and finally a 243 fl die, these steps were all done with the expanders removed. I then neck reamed the cases. They finished up about .030" short which is what the salesman at the gunshop where I bought them said would happen. Has anyone else had this problem?