Neither Hornady nor Nosler list D4350SSC. Hornady 9th, for all the 140 grain bullets, lists 36.9 grains as minimum and 41.4 grains as maximum, for IMR 4350 powder in 6.5x55. Nosler 9th also list for IMR 4350 for 140/142 grain bullets - 39.0 minimum and 43.0 as maximum. I had previously mentioned the rest of their respective recipes above - brass and primer. I assume, but do not know, that the two of them list loads that they pressure tested up to SAAMI maximum pressure levels, in their guns or their apparatus. Hodgdon 2011 Annual Reloading Manual lists H4350 with 140 grain Speer SP, Winchester case and Winchester LR primer. 39.5 grains minimum and 44.0 grains maximum.
SAAMI sets the pressure limit for 6.5x55 at 51,000 psi - found that on the kwk.us website. I suspect the North American makers use that number as a limit. If you chose to go beyond their recipes - you already are, by substituting a powder - sort of out on your own. Also note that CIP sets their limit for 6.5x55 at 55,000 psi - but although both use piezo testing - different procedures, different places measured. Again, I suspect, but do not know, that USA makers would be using SAAMI procedures to get a number. If you are not using the same primers, same powder, same bullets, and same brass, then you are not using "pressure tested" data. You are making your own - very prudent to start low and work up, rather than jumping in near the top end...
You can read various articles by John Barsness. He was questioning why he would "limit" himself to traditional pressure limits, in a rifle that is also made and sold for more modern, higher pressure cartridges. I use the terms "traditional" and "modern" somewhat tongue in check - he was talking about taking the 1905 9.3x62 up to the "modern" 30-06 levels - so was looking to arrive close to 60,000 psi piezo, without having the stuff to actually measure that. Various articles on "ballistic rules" etc. Took his resultant loads to Western Powders lab in Myles City, Montana to confirm - hence there are loads for 9.3x62 that he publishes that generally exceed "standard" loading material - he is not "guessing" what that pressure might be.
That was the series of articles where he discovered many of the traditional "signs" of pressure are not always dependable - measuring case head expansion, "reading" fired primers, tight bolt lift - sometimes worked on some of his rifles, sometimes did not, when wired up for a piezo pressure test. The only consistent one that he found was muzzle velocity - it moves lock step with pressure - accounting for barrel length differences. So, a 140 grain bullet from a 6.5x55, at 2,700 fps from a 23" barrel with N160 powder is very possible - at much higher pressure than Nosler was getting with that powder. No "fast barrels", no "special cartridge shapes", no "secret loading procedures" to get more velocity - just have more pressure.
