The standard 410 with Foster slug is about the same as a 38special.
I seriously disagree. It's not the same, its not even close, the .410 slug is more powerful than a .38 Special. Unless, you are talking about some light loaded brand I'm not aware of. I'm talking about regular Remington and Winchester 3" .410 slugs.
Winchester says their 3" .410 slug does 1800fps. Says so on the box. Now, even if we assume the factory is "enthusiastically optimistic" with that velocity, and throw away a couple hundred FPS that's still waaay beyond a .38 Special's velocity.
So, which do you think it is?? We've got people saying .410 slugs only do 7-800fps or so, and are equal to light pistol rounds such as .380ACP and .38 Special. And we've got other people who say .410 slugs do 1700fps + (and some of them have chronographs) and Winchester says 1800fps on the factory box. Who do you think is right??
I don't have a working chronograph (gave up on them decades ago, but that's a different story) but what I do have is the ability, and the experience of firing .410slugs, .44 Magnum, .357 Magnum, .38 Special, and 9mm Luger, and several other calibers, through the same firearm.
SAME GUN. Same frame, same weight, same barrel lengths, same everything, so firearm weight, shape, action type, grip angle, etc. DO NOT CHANGE. And while I understand how muzzle blast makes things seem different to some people, and is a calculatable factor, its not the most significant factor in felt recoil.
IT may not be something with precise numbers, but, to me, firing different loads from the same gun, and using the difference in the felt recoil is a reasonable way to roughly judge the approximate power levels of the loads compared to each other.
Out of my Contender, .410 slugs recoil more than .38 Specials, and 9mm. Very close to some .357 Magnum loads, and noticeably less than .44 Magnum loads. That's my hands on experience, and I shoot that same Contender in calibers ranging from .22LR to .45-70, so I've got a bit of experience. Take it for whatever you think its worth.