funny stamping on .38 special brass

[atr]

I picked up some assorted range brass this morning and was running them through my decapper/sizer when on of them "felt funny". I inspected the inside and found what looked like an additional thickness completely around the inside extending for about 3/16" of an inch above the flash hole. I looked at the stamping on the case and it was stamped "extreme 38 special". I picked up three of these and they all had the same feel in the press and all had that slight extra thickness on the inside of the case.
Does anyone have any ideas about what these are?
best and in Freedom
atr

[Winger Ed.]

They are a American company that makes hot rod +P self defense ammo.

I guess that's just the way they form their cases.

[atr]

thanks Ed, I thought it might have something to do with +P ammo

[35remington]

Make sure the capacity of the case is similar to other makes before loading them. Reduction in interior volume is bad in pistol cases.

[tazman]

Make sure the capacity of the case is similar to other makes before loading them. Reduction in interior volume is bad in pistol cases.

This^^^^^^^
There are some 9mm brands that do that type of thing. There brass cannot be used with normal loading data.

[Bmi48219]

….
it was stamped "extreme 38 special"…..atr

Was it stamped ‘extreme 38 special’ Or ‘Xtreme 38 special’?
I’ve seen the 9mm brass with an internal shoulder, can’t recall the manufacturer’s HS but IIRC, the name began with an M. (Mag-tech ?)
I’d be interested to know the distance between top of shoulder and the case mouth. And the case overall length. A step as OP described would make a fine shelf to seat a HBWC upon, if it were in the right spot. That probably wasn’t the manufacturer’s intention but it would show some forethought it it was.

[TNsailorman]

Less interior space mean higher pressure with a normal load or a +P load. Fill an empty case with a fired primer with water and weight the case. Then do the same thing with a normal case and see how much difference there is between the two. The thicker case will hold less water and therefore run pressure up with the same powder charge. If there is very little difference in the weight of the water between the two, I would not use anything but starting loads with those cases until I had a chance to see where I stood with them. Maybe load 6 with a starting load and see where to go from there. IN any case be careful with overly thick brass. Cauction is your friend in a case like this. Loosing a few cases would be better than maybe loosing an eye or worse. my take anyway, james

[atr]

since I have LOTS of "normal" .38 cases I've discarded the three "extreme" cases I picked up.
thanks again all
atr

[Boogieman]

Some 9 mm cases are made like that to prevent bullet setback