Minimum safe COL

[lazyengineer]

OK, so with the old time EXPERIENCED reloaders here, can someone please explain how switching brand of primer can do to the PSI and actual changes if they are all supposedly are to be to SAMMI specs? I have Federal and CCI mainly but have been using my few Remington primers up. And lots of people were saying during the shortage to substitute magnum for regular with no issues which i DID NOT. Or am i just ignorant? (Yes I know how the other parts of the cartridge can.)
Thanks & much appreciation for the answers.
Humbly,
Frank

In my own experience, very very little. I won't say all primers "are the same", because I do see different primer behavior itself. For example, S&B LR primers in a 6.5 Creedmoor with a skinny "high pressure" firing pin, will punch out a blunt the diameter of the firing pin, almost every shot. Where other primers do not. CCI400's will fail to light off a high-void charge of H335 in an ultra-weak load of 5.56, whereas otherprimers will work, CCI41's will light a small rifle primed 6.5 Creedmoor casing of 4064 at a very light charge and high void, where all other SRP in that load will fire .02-0.2 second delay hangfire in same. I have recorded a measurable amount of FPS better speed in using Blue Dot in 9mm when using magnum primers (but note, blue-dot is really too slow of a powder for 115 gr 9mm, so harder to light by a weaker primer). I tried SR primers in 9mm once, and coincidentally etched the crap out of the breach face on the slide with lots of gas-leaking around the primer diameter. I suspect the pistol pressure wasn't enough to swell the primer to seal right, so it leaked. They otherwise fired and ran fine though. I wouldn't use a SP primer in a SR, since I would expect those to punch or leak pretty easy - more than worry over ignition behavior if a standard load with little void space.

So yes, primer power level can play a roll in difficult to light powders. But when it comes to a more normal load with more typical powders, I've not really experienced one lick of difference when switching primers and for the most part just use them interchangeable, so long as same type. I don't retest a thing or worry about it at all any more. It's the gunpowder that makes it go.