The chambers may have been extended. I have a 315 that the chambers have been extended to 3" and I have shot 3" in it. I believe your's is the model 330 which is a 315 with walnut stock and grip cap. It for sure isn't a 5100.
My 315 measures .700 OD at 3 1/2". Assuming the bore is .410 (I have no way of measuring) that would leave .145 wall thickness which I believe to be sufficient. Later 315s were offered in 3". Maybe your's is one. RESEARCHER could tell us when.
The reason I say sufficient is because I own a 1929 Western Field made by Ithaca; the Western Long Range. It is marked 3" and the OD at 3 1/2" is .702; slightly larger than the Stevens 315,but not enough difference for concern IMO.
http://www.shotgunworld.com/bbs/viewtopi...7#ixzz1V82otwas
