I thought m17 receivers were made from nickle steel which would stretch rather than shatter like the over carburized 03 low numbers to avoid similar problems when they were manufactured. The only cracked m17 receiver I have ever seen was a Remington with a JA barrel. The rifle was also subject to other various forms of poor-workmanship done outside any factory. The crack was at about 11 o'clock as would have been viewed from the front of the receiver and was easily seen by the eye alone. Winchester already may have been using nickle steel in they're other offerings by that time as well if I'm not mistaken.