I do not subscribe to the method of looking at the case for signs of pressure. I noticed early on with rifle reloading, that the optical checking of a fired primer is an unreliable method of estimating how hot a load is. I observed contradictory indications too many times to rely on how primers look.

I prefer to measure for pressure, as described by Randy Selby on his YouTube channel.

A 1 in 10,000 micrometer was used to measure the diameter of the base just ahead of the extractor groove on the virgin brass. After firing, each case was measured again. For an increase in charge weight, there is a corresponding increase of that dimension. The numbers show that the case expands at that point, based on the pressure of the load.

This method does not measure pressure, it just indicates what each powder charge is doing to the brass compared to the rest. The powder that produces the smallest expansion is the lower pressure.

The primers look almost the same from the 245 grainers and the 300 grainers, across all the powder charges.

I'm including the picture of all the primers in the fired brass to show you that how fired primers look is not a reliable method to estimate relative pressure, no matter how good your eyes are.

The measured results of the Norma 204 and IMR 4955 illustrates the point of measuring for pressure. The Norma 204 load marginally exceeded the loading guide. The IMR 4955 load did not. The comparative measurement shows that there was less chamber pressure with 93 grains of 204 powder, 0.2 grains over book max, than 93 grains 4955 which is one grain over the starting minimum.

The measuring gives a much more accurate indication than you can ever get with your eyes.

According to Randy Selby, the most expansion you should have is 8 / 10,000 on virgin brass. In my case, the known lowest pressure load was the Norma 204 with a 245 grain Frontier Range Master, which gave 13 / 10,000 expansion. The 3000 fps velocity for the 245 grainer is in line with the starting load data from various manufacturers, so I am confident to use it as a comparative baseline. For example, Nosler states 2913 fps for a 260 grain Accubond with 92 grains of IMR 4350 as a starting load. This confirms to me that my lighter bullet at 87 fps faster from an extra 4 inches of barrel with a slower burning powder, is on the low end of pressure.

Possibilities :

• my starting loads are already over pressure

• or the chamber is a bit loose

• or the 7mm RUM brass is a bit undersize when new

• or my method of measurement is not entirely correct

I expect that because I am measuring with a flat anvil, not a point or ball, and I am not measuring exactly ahead of the extractor groove, but a little higher up, that my measurements are showing higher numbers than expected.

Based on the measurements, the indications are that Fiocchi Large Rifle primers produce a flatter pressure curve with N565 in this cartridge, and a good candidate for a ladder test. The velocity is not as high as with CCI 250 of Federal 215 Match, but 50 fps extra is neither here nor there, and I prefer to work with the lower case expansion number.

Overall, with the powders tested, N570 gives the highest velocity for the least relative pressure with Federal 215 Match primers.

The proof of wether of not the loads are over pressure will become evident by how many times the brass can be reloaded. If I can only get a few firings, I'll know that the 13/10,000 number is high to start.

These results tell me that to improve on N570, the powder must deliver 3000 fps with at most 12 / 10,000 expansion from my current batch of virgin brass, in this rifle.