S&B primers are pretty good and competitively priced: I use them, and have no hesitation in using them further. My only caution is, the SP and SR are indeed different. I used the SP (small pistol) in my 222rem, and most of them ruptured around the firing pin: My safety glasses and face received a light sandblasting, but bare eyes would hurt. These were not loaded to maximum listed either, so ensure that you are using the correct type.
The only question I have about the primers is how they compare to the more expensive CCI BR-2 or BR-4 and Federal Gold Match primers? Or is it unfair to compare them to match primers, rather than the standard line produced by other manufacturers.