That will depend on the stock material. Generally speaking, wood is good in the 40in-lb range, usually, and synthetics with aluminum bedding need about 60in-lbs, usually. Injection molded stocks (the "plastic" stocks with mold lines on them) usually respond best to somewhere in the 25-35in-lb range, but watch for stock deflection as it will happen with these frequently and will degrade accuracy. I've gone to "hand tight plus half a turn" for tupperware stocks, generally. If you find things loosening during shooting, go a little tighter next time.