No, amount of powder creates pressure. Amount of headspace can create uncontrolled pressure escape, as in not only out the barrel in the opposite direction of you.
We have ALL done it at one point or another, but please DO NOT READ PRIMERS. The fine folks who build ammo and rifle, that make-up SAAMI, found out quite a long time ago, that anything over about 45,000 psi isn't accurately reportable by copper crushers. They send the same lot of powder along with the same very carefully calibrated copper slugs to several different mfgrs, to test the reference load of some cartridge. Well with the same SAAMI min-spec test equipment, the reports varied in pressure by around 15,000 psi; so now they use strain guages.
So what does this mean? If the professionals who make billions of rounds a year can't accurately judge pressure with very carefully calibrated copper crushers, don't for one instant think that a NEVER calibrated primer cup, will report anything to a hobby reloader. Same thing with case head expansion. What alloy is your brass? What tensile strength is it hardened to? If you don't know, you would have now way of knowing when it even begins to stretch. Back around WWII lots of mfgs used an Olin alloy for 06 brass. That brass spec'd to be hardened to 89,000 psi. (Alloy C269, IIRC) So when you can measure that brass growing you know you are generally way beyond 60,000 psi...
Use your chronograph, or buy a Pressure Trace system if you want to know pressure.
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