For what it's worth.
I managed to sneek a day off and go up to the range last Tuesday morning to do a quick test using Federal 205m primers and compare with my archived murom kvb 223 test results from a few years/800 rounds-ish back.
Rifle is a tikka tac A1 6.5cm, lapua sr brass, N160. Temperature was around 8C (very mild for the time of year) and very little, if any, wind. Standard harris type bipod and rear bean bag. I did the following tests at 100yrd:
Firstly for safety, a single round going up in 0.5gr increments from my lower node charge weight up to my higher node charge weight to check for signs of pressure. No over pressure signs so on to my mini test.
3x rounds at my usual highest node powder charge: 8.5mm group.
3x at -0.3gr: 7.5mm group.
And then:
3x rounds at my 2nd node down: 5mm
3x rounds at +0.3gr: 10mm
3x rounds at - 0.3gr: 5mm
Comparing the groups with one's done using murom kvb 223 primers some 2 years back it appears the 2nd node down has shifted ever so slightly down in powder charge some 0.2gr if that. The higher node has spread out by around 2mm and again shifted slightly down on powder charge.
So for my rifle, Tikka Tac A1, changing from Murom kvb223 to federal 205m primers will mean reducing my charges down by 0.2gr to stay in the sweet spots. However what I haven't managed to do yet is measure muzzle velocity for consistency and I only did 3 shot groups and not 5 like I should have done but bullets, powder, primers etc are getting bloomin expensive.