looking for brass for a 243win i do however have a large quantity of .308win brass can i just run this through a .243 FL sizing die or do i have to gradually go down or should i just get new brass?

I have just run .308 thru a .243FLS die with no problems, except you end up with the wrong headstamp, and they are a bit shorter.

Gentlemen:

I'm posting out of curiosity.

I read an article more than 25 years ago about a .243 rifle blowing up. The owner was necking down milsurp .308 to .243 and the blow up was blamed on the neck walls being too thick.

If the claimed cause is indeed fact, would turning the necks to correct dimension make everything OK?

Sambar,

I'm in 100% agreement with John from SC.

To John's query about the finer points of working the brass, yes. If the inside/outside of case necks are either reamed/turned and the loads adjusted (deceased) for the increased thickness and softness of military brass (including the primer crimp removed) everything works just fine. Alot of extra work but when you're young, energetic and finacially strapped - it eventually worked out O.K. for me, after the following.....

When I started reloading about four decades ago, I thought the same about simply running the .308 brass (read: lots of military surplus, I was in an Infantry batallion at the time!) thru a .243 die. The idea works great in concept because the .243 is the .308 necked down.

BUT I found out that my .308 cases necked down to .243 actually required either inside neck reaming or outside neck turning due to the case necks being way too thick whent he bullet was seated. After a much more experienced reloader showed me the error of my ways since there actually wasn't enough neck clearance for the case necks to expand when the bullet was fired in my chamber. Thankfully the .243 was a Remington 788 of apparently great strength because the pressures must have been tremendous!

Net, this could work just fine depnding on alot of variables or you could be be creating dangerous pressure levels.

Make sure you consult with someone more experienced or has the measuring tools & ability to ensure you're within specs before just loading em up and firing!

quote:

Originally posted by sambar1:
looking for brass for a 243win i do however have a large quantity of .308win brass can i just run this through a .243 FL sizing die or do i have to gradually go down or should i just get new brass?

sell the 308 brass and buy new .243 brass is my recommendation.

If the 308 brass is military that causes more issues.....good stuff but needs to be loaded differently.

Brass really isn't expensive so buy a bag of 100 and get on with shooting.

vapo - D......

After my lengthy discourse above, as usual you're absolutely correct!

Well I had no pressure problems. I certainly didn't blow up.

I personally wouldn't care to have ammo with the wrong headstamp sitting around. Maybe I'm overly cautious.

.243 brass isn't expensive or hard to come by. I would just buy new stuff and hang on to the .308's. You may "need" them someday. Let me take a look around, I might have some brass we could do a trade on if you're interested. I gave a bag full of .243 brass to my neighbor last year, not sure if that was all of it or not.
Good Luck

New and 1x brass is cheap. So unless you'd rather spend shop time instead of range time, just get some proper stuff.

quote:

Originally posted by sambar1:
looking for brass for a 243win i do however have a large quantity of .308win brass can i just run this through a .243 FL sizing die

I did exactly that with FC match brass, without neck turning and did indeed find there was minimal diametral clearance around the neck.A number of bench rest shooters predicate this scenario for greater accuracy. That being said I worked up loads starting low. There is a difference between .001" clearance and jam, tight or press fit. Even if the potential danger is real but insignificant use the cautious approach.

I probably reloaded these cases twice before I put them aside to be use on wildcats. roger

I could run thousands of 308 rounds through a 243 sizer, shoot them in a .243 and never have problems.

But I would not tell my kids to do that.
They can't park a car without hitting something.
They screw everything up.
They would not think to measure their chamber and their loaded case necks.
They need idiot proof systems.

What does it all mean?
Some handloaders can do cartridge converstions safely.
Others handloaders may not be at that level of expertise yet and should stick to the instructions in the load book.

Tnekkcc, just so, but the one and only gun (revolver) I blew up was when I WAS following a book.

With the 308/243 business I was well under Max on purpose, the bullets seated "normaly", the loaded rounds fitted in the chamber EASELY.
So then I took a little chance and fired one.
Then when the empty case is a loose fit on a bullet I relaxed a bit.

But sure, it's one of those things not worth doing normaly. EG John J. Donnelly's book on cartridge conversions states to use .270 Win. cases, Anneal neck, FL size without expander, trim to length, chamfer, FL size, inside neck ream. etc. which is another way of saying go buy factory .243 brass.

thanks everyone i thought there may have been something else to it than just running it through a FL die ill stick with the new brass bit safer as at this point in time i know very little about turning necks nor do i have the equipment to do it so ill just stash the .308 away until i can talk the local gun shop in for a trade.

quote:

Originally posted by tnekkcc:
I could run thousands of 308 rounds through a 243 sizer, shoot them in a .243 and never have problems.

But I would not tell my kids to do that.
They can't park a car without hitting something.
They screw everything up.
They would not think to measure their chamber and their loaded case necks.
They need idiot proof systems.

What does it all mean?
Some handloaders can do cartridge converstions safely.
Others handloaders may not be at that level of expertise yet and should stick to the instructions in the load book.

This post makes me wonder which of your two categories you belong to... You certainly seem prepared to make blanket statements on public Internet boards, where (less experienced) reloaders make take your miserable advice.

Have you made this cartridge conversion? If yes, have you established the the difference in neck wall thickness between factory .243 brass and necked down (military) .308 brass?? Have you measured loaded round neck diameter of .243 rounds loaded in factory and necked down .308 brass?? Do you know how much neck clearance is required to safely shoot a cartridge?? Do you know the neck diamter of your chamber??

You *may* have done the conversion, and have gotten away with firing the loaded round in *your* .243 chamber. In fact, you may have a sloppy chamber - hardly anything surprising in a factory gun. But do you know the neck diameter of the chamber of the people whom you advise to perform the cartridge conversion?? Do you feel that is a safe way of offering advice??

I come back to my statement: Your post makes me wonder which of your two categories you belong to...

- mike

Take a 308 run it into a 243 sizer, load it and measure. If you have to thin the neck (a maybe) try using an outside turner. If you have an oversize neck the neck can't expand enough to release the bullet, and pressure goes up. If you have already fiired a resized case check if the bullet will enter the un-resized neck. If it will you are ok.
Good Luck!

quote:

Originally posted by John in SC:
Gentlemen:

I'm posting out of curiosity.

I read an article more than 25 years ago about a .243 rifle blowing up. The owner was necking down milsurp .308 to .243 and the blow up was blamed on the neck walls being too thick.

If the claimed cause is indeed fact, would turning the necks to correct dimension make everything OK?

YES!! Hawkins is right!! One might have to turn down the case necks to the proper thickness after resizing .308's to .243! The case mouth must be able to expand sufficiently to FREELY release the bullet on firing! Otherwise, you are courting disaster!!

Sambar1,
Neck reamers (preferred for necking down) and outside neck turners are attachments for case trimmers. Some mfgr's have them for their products, others don't, so it depends on which brand of trimmer you use. It's not rocket science to do the conversion, and the dangers and cautions have been well illustrated here. The most important tools you need for doing conversions are an accurate vernier, dial, or digital caliper, and a neck thickness micrometer. Case forming lube doesn't hurt, either. A fired .243 case from your rifle will give you the necessary information on the size of your chamber and neck thickness. It's good to know how to do it, but is it practical in this instance? Probably not. New .243 brass is cheap and easily found - for the cost of the tools you would need, you can likely buy a thousand or more. Too, the possibility of confusion with the wrong headstamp on the case while not a big deal going to a smaller caliber is still not an ideal situation. If you are necking up instead of down, headstamp confusion can be deadly.

quote:

Originally posted by mho:
[QUOTE]Originally posted by tnekkcc:
I could run thousands of 308 rounds through a 243 sizer, shoot them in a .243 and never have problems.

I come back to my statement: Your post makes me wonder which of your two categories you belong to... - mike

tnekkcc, have you pissed mho off? Been waiting to use this little jem! roger

Roger,
You are an engineer too.
Surely by now you have figured out that talking about handloading to non technical types will piss them off. Just ignore any posts with no technical content or wit. Give up the last word, and save your strength for something more interesting.

308 Calculations
The SAAMI spec for .308 cartridges is .3355 to .3435" loaded with a .306 to .309" bullet.
To meet SAAMI specs for loaded cartridges with all allowable bullets, the case manufacturer must then produce cases with loaded thickness that must be at least [.3355 - .306] /2 = .01475" and no thicker than [ .3435" - .309] = .01745"
The cross sectional area of a circle is = pi r squared = pi [diameter/2] ^2 = pi/4 [diameter]^2
The cross sectional area of a ring [the case neck] is the cross sectional area of the outside minus the cross sectional area of the inside
Ac = Aod - Aid = pi/4 [OD^2 - ID^2]
For the cartridge to comply, the brass would have to have a neck cross sectional area between pi/4 [.3355"^2 - .306"^2] and pi/4 [.3435'^2 - .309"^2] = .014863071 and .017680294 sq. in
Knowing the case inside diameter after resize and the brass neck cross sectional area, one can solve to the outside diameter:
OD = root [ Ac 4/pi + ID^2]
The neck thickness would then be:
T = [OD - ID ]/2
T = [root [4/pi Ac + ID^2] -ID] /2
With resized or new .308 brass, the ID is typically .300" and we would expect to measure thickness of:
Tmin = [root [4/pi .014863071 + .300^2] - .300] /2 = .01501837"
Tmax = [root [4/pi .017680294 + .300^2] - .300 /2 = .017713483"

243 Calculations
The SAAMI spec for .243 bullets is from .240 to .243".
Loading .243" bullets in .243 brass with a cross sectional area of ..017680294 would give a loaded neck diameter of:
OD best = root [ Ac 4/pi + ID^2] = root [.014863071 4/pi + .240^2] = .276630168" [best case small bullet and thin neck ]
OD worst = root [ Ac 4/pi + Di^2] = root [ .017680294 4/pi + .243^2] = .285587551" [worst case large bullet and thick neck]
The 243 necks made from .308 brass would then be between .018315084 and .21293776" when loaded.
The SAAMI spec for .243 chamber necks is from .277" to .279".
This makes it look like if there were a uniform distribution of brass within what SAAMI allowed, only 25% of the necked down 308 cases would fit in a 243 chamber.


Measurements:
Taking 6 pieces of .308 brass and chamfering the necks [I don't want to measure the burr] and then sizing them with an RCBS FL sizer:
a) RA 61 brass .300" ID, T = .013", upon resizing to .243 = .016", when loaded with .2430" bullet, neck = .278"
b) New Win .308 brass .300" ID, T = .013", upon resizing to .243 = .016", when loaded with .2430" bullet, neck = .273"
c) FC new 308 brass .300" ID, T = .015", upon resizing to 243 = .019", when loaded with .2430" bullet, neck = .2835"
d) FN 78 Berdan brass pulls, .300, T = .015, upon resizing to .243 = .018" when loaded with .2430" bullet, neck = .282"
e) FN 78 Berdan brass pulls, .300, T = .015, upon resizing to .243 = .018" when loaded with .2430" bullet, neck = .2805"
d) FN 78 Berdan brass pulls, .305, T = .016, upon resizing to .243 = .018" when loaded with .2430" bullet, neck = .282"

d) .20155" long before .243 sizing, .20175" after, = .006" length growth.
308 brass has a max length of .2015, and adding .006" would make it .2075"
243 chambers have a min length to end of neck of .2055", there could be interference without trimming length.

With a new unfired Remington 700 take off barrel, a .2780+" pin gauge goes and a .2790+" no goes.
b) Winchester case drops in.
c) FC case no go
a), d), e), and f) start to go in with a few ounces push with the finger.

My .243 reamer measures like it is .278", and would probably make about the same hole that Remington made.

When I have to push down on the bolt handle with 100 pounds of force to get .308 brass to chamber in a .243, about 66% of the time with a 40 gr. IMR4895 100 gr. 67,000 psi load, the pressure goes so high, that the primer falls out.


What does it all mean?
Sometimes necked down 308 brass fits in a .243, sometimes it does not.
Part of cartridge conversion is checking fit.

I'm not sure who is having a go at whom.
I was the first to give advise, the poster asked if it could be done and I said it could as I had done it.

I'm not going to panic about giveing danger warnings for every possible problem, but I was lax and uninformed about neck thickness.

I ordered a rifle and ammo for a friend once and he started to shoot it before I got back to him. EVERY shot he had fired had blown the factory primer RIGHT out. All beyond me. Did you clean out the bore before firing was all I could think of. Did I nearly kill him by getting him a rifle?

Apparently.

quote:

Originally posted by JAL:
Did I nearly kill him by getting him a rifle?Apparently.

Not hardly. The brass case is like a fuse in an electrical circuit. It'll destruck long before the steel gives. I shutter to think of the possibilities of what might happen if we reloaded those steel cases. Bye bye safety valve. roger

quote:

Originally posted by JAL:
I ordered a rifle and ammo for a friend once and he started to shoot it before I got back to him. EVERY shot he had fired had blown the factory primer RIGHT out. All beyond me. Did you clean out the bore before firing was all I could think of. Did I nearly kill him by getting him a rifle?

Apparently.

I don't think so either. If he's old enough to handle and shoot guns, cleaning and inspection of a new or used rifle is one of the basics after pointing in a safe direction and checking the chamber. Never mind the ABC's of overpressure signs that he completely ingored through either ignorance or stupidity. Now don't get me wrong here, I have friends that operate on that level, too, but I don't hang around them when they're holding anything more dangerous than a beer can.

It just brings Darwin to mind, and I don't mean the city in OZ.

Ignorance and stupidy,? well you forgot young. Same thing sometimes. We were both 17 year old Jackeroos finding our way. His first rifle, my first example of poping primers out.

I THINK, as I asked around later, Sako, about 1962 were selling Red box ammo and Blue box ammo. Maybe the Red box stuff was hotter.?
The same gunshop that helped me blow up a revolver (partially anyway) sent the red box to the tropics in Northern Aust. About 120 in the shade. And I know these gunshop clerks can be uninformed also, because I was one.

Anyway last I heard we were both still alive, me just.