Cheers mate I really appreciate your help!
I was asking because I hope to get my Merkel 140AE (also in 450/400 & made 2011) regulated with my home loads, still in early stages yet, I have tried AR2208 & my best with that was 77gn, its 4 shot group wasn't too flash at 50m compared to most here, about 90mm x 30mm (2 1/2" high x 1 1/4" wide).
I will be trying AR2213SC next, with 80, 81 & 82gn is on the check list to do so will keep an eye on your load especially.
Also will try AR2217 89, 89.5 & 90gn after that.
My initial loads for all powders were all done with virgin Hornady brass, Woodleigh 410" & Federal 215 primers.
Group size changed dramatically after using fireformed brass for the AR2208 loads that were rechecked to see how they go.
Special thanks to '264' & '450Ackley'for their advice pointing me in the right direction - thanks guys!
Speaking of chambers, the chambers in my rifle are quite 'generous' to say the least, hence group size etc changed.
I've not been able to chronograph any loads on the occasions that its been shot, its seems I have developed a jinx on both of them at present, weird errors or not working at all! Batteries (9V) were still producing good enough voltage, but seem to die under load. New batteries put in & checked for operation....fingers crossed for next test.

I have a good mate who is thankfully doing these for me as I've developed of all things cancer early on in the year. This bloody thing has severely affected my back so I can't lift much at all, try not picking up a crying 2 year old grandchild; I can do it now (very carefully) after radiation & 5 solid months of chemo.
It painful to watch someone have all the 'fun' but I'm learning as I go reloading for this one, I really enjoy the reloading side of things so it's not all bad for me! My youngest lad had his first crack at it the other day & shot some Hornady factory loads off hand at 25m, 2 shots side by side 1" apart, father & son were pretty happy, now to get my loads sorted before going into hospital for the big crack at this cancer.
Not sure how bad your barrels foul, but these are frightfully bad! I can scrub literally for hours & hours on them for what seems like little gain. I ended up plugging the bores & squirting Eliminator down them & leave overnight muzzles down!

Will keep you informed on my progress.
Cheers
93x64mm