Looking to an alternate powder for .223 26" heavy barrel bolt gun other than H335 I bought a pound of 8208 xbr. Made (3) test loads each starting at 24.3 24.6 24.9 25.2 Using 55g V-max with a OAL 2.250 here are the results:

24.3 fps 3122, 3094, 3112 group size .620
24.6 fps 3193, 3165, 3174 group size .710
24.9 fps 3245, 3212, 3261 group size .512
25.2 fps 3321, 3332, 3344 group size .367

It seems this powder performs better at closer to max levels.
there were no signs of pressure at 25.2 which suggests I could increase load volume if desired (book values 23.0 to 25.3 max) However, i'm happy with the velocity i'm getting. I will adjust OAL and search more for the magic spot before increasing load.

My understanding from guys using if for Highpower competition is that this powder really spikes the pressure as you get up there at max. Not as linear as H4895 for instance. So go slow and make small changes like you have already. I have a pound but have not tried it yet.

It works great in my remington 700vtr 308 43gr and a 168gr matchkings

I use it in a match gun with 75gn and and 77gn bullets. It performs well but does get spikey.

Good to hear the firsthand experience and the spiking issue. I need to try some in a 338 Federal. Hows the temp stability?

Great in the 35 Whelen. 200 accubonds with 57gr at 2750 and moa

Are we looking at a relatively narrow window of opportunity between optimal near max performance and spikes?

DF

I'm 100 fps faster with the exact same charge except I have a custom 24" barrel and used CCI 250's. Shoots great and is one of my favorite loads.

I have never noticed any pressure problems but don't hot rod my loads which I think is the real source of "pressure spikes"

^^^^^
Exactly, except my .308 is a 5R. One hole at 100 yards.

I have used IMR 8208 XBR in two 6 BRs and a 30 BR. I have loaded beyond max with these chamberings to learn what the limits were and there were no spikes.

I've never had to load it up really high to get the MV I was looking for or great precision; my experience is confined to 75-77gn in .223 Wylde and 175gn in .308 Win although I will use it under 123gn in a Grendel soon. I do find that it gets spikey if you are using a compressed load sort of like RL17. More than anything I find that I get really high port pressures and over gas in AR if I use hotter loads of 8208.

Works well in my 7-08...very well.