I sure hope not, because my Miroku/Winchester .45-90 has that same thing stamped on it and it has shot only smokeless and often at big game pressures.

I looked into that message/warning and it was "lawyer talk" because there was no SAAMI specification for the current .45-90 rifles.

[Linked Image from jpgbox.com]
Not flashy, but solid and effective. AND, it handles Factory .45-70 ammo too!
The folding tang peep and folding barrel sight are from Marbles and make a nice combo.

CRS, NRA Benefactor Life Member, Whittington Center, TSRA, DWWC, DRSS
Android Reloading Ballistics App at http://www.xplat.net/