Though 'recoil' is identical for both shells that generate identical velocities, can the human nervous system detect that brief period of a higher rate of acceleration? Are some 'mild' loads able to 'pop' a shooter's shoulder and cheek sharper than others?
Some can, yes...............without a doubt I can. And it has nothing to do with pain at all. It
feels like it is the duration of the recoil ......... "pop" or "push". When I switch loads sometimes is when I notice it. After the first few rounds that difference fades and is no longer noticeable to me.................until I switch again.
As to the pressure having any effect on the standing breech, I have changed my mind on the matter. I now believe it does. To draw a comparison with a rifle cartridge, one of the signs of too hot a load (too high chamber pressure) is flattening of the primer. The only way possible for the primer to flatten like it does is for the head of the case to move against the bolt, be it a rotary or falling block, or the standing breech of a double rifle. Granted, we are talking about much higher pressures in a rifle cartridge, but that doesn't change the principle. The primer is flattened because pressure is exerted on the case/shell head, from the inside of course, forcing it against the breech face, whatever type it may be. I can find no other possible explanation for flattened primers in hot loads than that. The pressure tries to blow the primer out of the pocket, but cannot because it has met an "immovable" object, so it deforms it into any space available. I understand steel flexes, so please don't take me to task for using the term immovable.
SRH
