The CCI-350 I think is the hottest American made magnum primer by far. I think John Linebaugh discovered the same pressure spikes when using Hornady testing equipment.

I doubt you will ever see peak pressure spikes with other American made magnum pistol primers, as you will see with those CCI-350's. Many years ago John Linebaugh recommended WLP's to me for use in the 500 Linebaugh Maximum and I've been very happen with their performance in all temperatures and with all powders.

I still have a good supply of CCI-350's and load them now & again in 44 mag and 45 Colt and I haven't been able to tell the difference relative to accuracy between the 350's and WLPs and Federal 155's.

In -20F I have found the WLP's and 155's set off H110 with the aforementioned cartridges just as well as the 350's, BUT if I knew I would only have one shot in the cold weather, I'd load with the CCI-350's every time, just cus.

Now for the OP's question, I sometimes use IMR-4227 in my 475 linebaugh and haven't found the accuracy to fall off with a hot barrel, but that's at 25 & 50 yards, as when shooting 100 yards I don't think my barrel gets really hot, as I don't shoot as fast or as many rounds as I do at the shorter ranges.

27.0 grains of 4227 with a 325 cast gets me 1,130fps, 26.0 grains with a 375 grain cast flies at 1,115fps and 21.0 grains with a 400 grain cast bullet goes a comfortable 920fps. This is from a 5.5" "cold/cool" barrel, as I normally fire over my chronograph with a cool barrel before I start shooting for group/score or minute of beer can.