Firecat,
Some of the more extensive tests that I've seen done on this topic have been posted over on 6mmBR.com, since they're more competition oriented. German Salazar has done some and written them up beautifully, as he usually does. Some years back, there was also a series of tests done by Bob Jensen (Jensen's Custom ammo; he loaded the ammo for the '92 Palma Matches fired at Raton that year) using a series of photos (essentially, spark photography) of primers detonating against a grid paper backdrop. This allowed you to actually see/measure the varying degrees of brisance between various primers, and the difference is tremendous. I recall that he also chambered up a centerfire rifle action in the format of what became a very high dollar BB gun; a case modified to be loaded with a standard .177" steel BB, with a very short "barrel" that allowed him to chronograph the BBs with the primers being the only variable. Very interesting results in terms of SDs and ESs denoting the consistency of each of the various makes of primers.
That said, I should caution, primers change. Manufacturers make adjustments to their compounds, their cup thicknesses, anvil designs, etc.. These tests should give you some inkling of just how much difference there is between the various makes, but I wouldn't assume that the primers today are exactly the same as what the results that these tests show. As a general rule, you want a primer that's capable of giving complete ignition, and no more. The less violence or shattering effect (brisance) that a primer generates, the better it is for accuracy. Balancing that, the primer has to be capable of reliably igniting that powder charge, or we get hangfires, poor accuracy and other annoyances. The 215s are probably the most violent primers out there, but for a very large case stuffed with a big dose of slow burning powder, they're still the go-to choice for priming. I just wouldn't use them for a 308 Match gun, since they'd be out of place there. Regardless of the combination we're talking about though, it pays to do some work to isolate a good primer/load combination. It may not make the slightest bit of difference at 200 yards, but it certainly will at five times that distance.
As far as the Fed 210s and 215s, I use both, but as I said, they both have their place. Ditto for most others. One other thing I'd stress here is, don't get too married to a single primer. Some years back, most of us Service Rifle shooters were using the same make of primer, and all of us were quite satisfied. Then we all suddenly started having major pressure problems, or pressure signs, anyway. No other changes in the loads, but we all suddenly started blowing primers. Pressure testing showed that our loads were still within the boundries, so the change was in the primer itself. Turns out the manufacturer decided to increase sensitivity of their primers (which none of us had problems with!), by thinning the cup ever so slightly. The result was a major problem for us, and this community left them in droves. Today, they're now a very minor player in this particular competitive community, and you rarely see them being used these days by Service Rifle shooters. My point is, things change, and you should never take these things for granted.
