Charge reductions for military brass

[thomis]

I'm loading some military brass .243 Win and .308 Win.
I understand this is heavier/ thicker brass and the charge amounts need to be reduced. Is there a standard amount that applies to both calibers, i.e. 10%?
10 % seems like a lot, by the way. A mid-range load using H-4895 for a 100 grain bullet (.243) with a minimum charge of 31.0 grains and max charge of 33.0 grains would be 32.5, reduced by 10% would be 32.5 - 3.25 = 29.25 putting it below the minimum charge.
Correct me please, for I must be wrong. And no, I don't know where I came up with 10%

 

[rcmodel]

There is no need to reduce any further then the Starting load data with any brand of case.

Just start there and work up as usual.

Did you make the .243 out of .308 military brass?
Because there is no military .243 brass.

If you necked down .308 to .243, you need to check the case neck thickness, as it will probably need to be neck turned or reamed.

If it is too thick, there is no room in the chamber for it to expand to release the bullet.

rc

 

[thomis]

I do believe the .243 brass is .308 military brass necked down. But this would have been done by my Grandfather, and before he had the chance to explain it to me. I'm going through the last of the last of my reserve rifle brass and this stuff hasn't been touched for 30 years. There are only 20 or so pieces of the military .243 brass, I think I'll just leave it alone.
But I have enough of the .308 military brass to learn how to work with it.
As always, thanks for the help.

 

[45lcshooter]

I was going to say, I've never heard of 243 military brass.

And you really don't need to watch your loads until you go to the higher range. I think its10% reduction for higher loads.

 

[Ifishsum]

If your goal is to use a proven load from commercial brass to military brass, and your load is not pushing the max you could probably drop 5% and do a little workup from there to see what difference there is. If you're at or near max load I would back off 10% (or use book starting load) and go up carefully from there.

 

[Slamfire]

You need to search for posts about pressure problems people have had swaging 308 military brass down to 243.

It is my recollection that a number of people have reported pressure problems because the neck was so thick that it pinched their bullets.

Unlike greases and oils which will move under pressure, brass won't.

 

[Clark]

On 9-12-2003, I shot these handloads in a 1938 Turkish Mauser [that I rebarreled to 243]
Not only did I have to pound the bolt open, I had to pound a case out with the cleaning rod.
There was probably some neck pinch. It took about 100 pounds of force at the bolt knob to get the round to chamber.
CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.
All three were the same load 40 gr 4895 100 gr 243, LC brass necked down to 243.

What does it all mean?
The 308 military brass, necked down to 243, had too much neck wall thickness for the standard SAAMI 243 chamber. The pinched bullet had a high starting pressure, and the powder burned for a while before the bullet moved. That changed the peak pressure, as seen in brass deformation.

What does THAT mean?
I should have bought 243 brass, or reamed the necks or turned the necks.

 

[noylj]

The initial point should have been:
No, there is no "rule of thumb."
You always work up your loads from the LOWEST starting load you can find (reference at least two independent reloading sources).
You always check case length and neck thickness with bottleneck cases.
There are no short cuts.