Pre pandemic, or as soon as I saw c-19 getting into the USA, I bought all the primers I could find. I also posted that it might be wise for others to do the same. Anyway, part of what I got was #7 Small Rifle Bench Rest Primers by Remington. I've got primers by just about by anyone who made them. Small pistol primers soon got the hardest to find. The question here is, what makes Remington's call these Bench Rest?
There has been some great information provided in this thread!
Take a look at this:
Mysteries And Misconceptions Of The All-Important Primer
http://www.shootingtimes.com/2011/01/04/ammunition_st_mamotaip_200909/
A bud of mine used to go to a Military Ammunition plant, and since he was interested in small arms, was interested in the processes. He told me that primer cake is mixed by hand. And then it is tested in a "mule". The information this mule provides was amazing, I know he said mass ejected, surely there was dwell, time to peak, flame temperature, energy, duration, and a bunch of other variables I can't think of. The worker whose primer cake was the most consistent, got a cash award. And who got the award, changed. Making the best primer cake of the day was not a sure thing. I wish I knew what parameters were measured.
You can expect primer cake to differ from day to day, as the percentages of the ingredients are plus or minus
The military primer mix is or was the FA 956 mix,
PATR 2700 Encyclopedia of Explosives Vol 8 gives the composition
FA 956
Lead Styphanate 37.7 +/- 5%
Tetracene 4.0 +/- 1%
Barium Nitrate 32.0 +/- 5%
Antimony Sulfide 15.0 +/- 2%
Aluminum Powder 7.0 +/- 1%
PETN 5.0 +/- 1%
Gum Arabic 0.2%
Given that percentages vary, and that ingredient purity varies, I am certain primer ignition characteristics also vary. However, we the public have no idea what the variances are, as the manufacturer's are not releasing that data.
From articles past, the Federal "Match" and I assume Remington Bench Rest, are primers that are more consistent in test, at the end of the production line.
We don't know the sample size. Lets say forty primers were tested per lot, and the best lot gets labeled as "Bench Rest" and sold at a ridiculous mark up. Is 40 primers enough to prove an entire lot of 100,000 primers (guess) is superior to other lots of 100,000 primers?. I don't know, and I am going to say, until we understand what characteristics are being tested, the limits of these characteristics, the number of primers tested, the lot size, we really don't know much about the goodness of the primers, do we?
