So...I was "called out" on another forum when not subscribing to the proposition that all primers are created equal, in that accuracy was not affected by the brand of primer. That proposition made it over to this forum, so I am posting here as well.
The test: five, 5-round groups fired at 100 yards from my 1917 Winchester Mod Scope rifle, in a Boyd sporter stock with an Athlon Midas BTR Gen 2 30 mm scope, 4.5-27x. Powder was 17.5 grains of 2400 weighed, under bullets sorted to 0.5 grain, and cast 22 bhn, from a mold made for my throat and barrel. The rear band measures .311, the nose .302 that is engraved by the rifling at 3.35 COL when chambered. The barrel was a virgin 1919 NOS 5-groove when I purchased it and has never seen a jacketed bullet. The cases are LC 67, weight sorted to within 1 grain, trimmed and neck turned, with reamed flash holes; this lot has been fired 23 times with periodic torch annealing.
Primers tested were Remington 9 1/2 and 9 1/2M, Federal 210, Winchester LR, and CCI 200 seated just below flush with a Frankfort hand primer. I did not use any large pistol primers. I used the 27x setting, and fired over a front rest and rear bag with a very hard hold. Weather was balmy in the low 60s, variable light breezes, and the grass was 2.5 inches high. I was too lazy to set up my chrony, gonna have to budget a LabRadar some day.
After zeroing, five, 5-round groups were fired, the results are shown on the enclosed target.
Remington 9 1/2 - 2.20" by 1.63" group
Remington 9 1/2M - 2.65" by 1.78" group
Federal 210 - 0.88" by 0.72" group
Winchester LR - 0.80" by 0.76" group
CCI 200 - 0.69" by 0.29" group ( I pulled the last round at 2clock)
Conclusion: While this was not a statistician's 100 round group test, I'm not going to cast up 500 weight-sorted bullets to do so - the differences between brands of primers are obvious. My rifle prefered Remington 9 1/2 primers when using my stash of 4759; grouping went to pot with 2400. Clearly, I'm using CCI 200s with 2400 for now.