My previous work with my Marlin XL7 30-06 with a 22" barrel produced over 3,000fps with a 165gr load and three rounds being tested with a strain gauge averaged 63,751 of pressure and certainly this is a +P 30-06 load if there was such a thing out there certified as a +P load, but there isn't, so it is time to back down as I already have. Will be posting in the near future on this thread new load results for a variety of bullets, powders, primers and brass along with OAL data.
As far as my action being a modern action and stronger action than older rifles which can't and should not handle these pressures in the 63,000 range, neither should I continue in theses ranges with my modern action. There is no reason to push my rifle to the edge when I can use a 300Win Mag if I want over 3000fps with a 165gr bullet.
Frankly, I am more than satisfied getting in the low 2900fps out of my 30-06 and a 165gr bullet, not pushing the envelope or my rifle while having outstanding velocities for my 22" barreled 06 and better accuracy to boot. I do believe judicious load development and careful planning of my method of moving up in load charges in very small 2 tenths of a grain increments, as well as using different types of brass (Remington and Winchester) along with different primers (Rem 9 1/2 M, 210 fed, CCI 250 and Rem 9 1/2) to see how these combinations worked with each increase of my powder charge. This proved to be very beneficial in not being to extreme in my final load, although it was a hot load. Now I am using as stated above a reduced load and it falls in the low 2900fps range.
I think the 30-06 has so much potential that is untapped (always believed this of the 30-06) now that we have new actions, powders, and a very large variety of bullets to do so much with the 06 in the years to come. I do love the 30-06 and always have, but the days of IMR4350 being the best powder for the 06 over the spectrum of bullets weights available are long gone, although it is still a good powder to use for the 06 with some bullet weights, but no longer the overall best powder for the 30-06.