.270 WSM brass selection

[kab]

I am in the process of developing a load for my 270 wsm. I have started off with Federal brass, Barnes 130 gr TSX, Federal magnum primers and the powder is reloader 22.
I started off with 67 grs, then went to 68grs then 69 and 70. All of them showed no signs of high pressure with the exception of 70 grs, and even then, there was only slight flattening of primers , the bolt opens easy and all the fired brass measured well within spec.
I then purchased some Remington brass, and loaded up with the same idea in mind as the results the federal brass gave me.
This time i had started off with 69 grs, then 69.5 grs and finally 70 grs. The grouping on all three loads were within an 1" at 100 meters. But the 69 gr load showed no pressure signs,and the 69.5 showed slightly,and on the 70 gr load I had a sticky bolt and an ejector mark.
So here is my question, do any of you have some tangeable experience of the way different brass reacts with the same load configuration?

 

[Jeromey]

I have not used two different types of brass for the same load yet but do have some insight for you. When we test ammunition for pressure we need to figure out the slope and offset of each, the slope being the one that will change the pressure readings. We put the brass into a fixture that also holds the test transducer. Depending on the type of round it will depend what pressures we pump up to, usually a number of different pressures up to about 60,000 psi. We then input the reading from the charge amp and corresponding pressure into a computer program and it gives us the two numbers. In simple terms the slope is how soft the brass is. There is a wide variance between different manufacturers, as well there can be a difference within the same manufacturer from lot to lot.
The internal case capacity would also play a difference in your loads. If the Remington case has less volume than the Federal you will get higher pressures.

 

[kab]

Thank you for your reply, so could you give me some insight as to what brass generally handles larger powder charges better then others without demonstrating pressure signs?