Can you use 22LR in JC Higgins Model 103.18 22 cal bolt rifle?

Your rifle is a Marlin Mdl 100, made for Sears under the Sear brand name. It was chambered in 22 LR, (and can also use .22 Longs and .22 Shorts) Caliber is generally marked on the barrel. It is prudent to have our rifle checked by a gunsmith before shooting for safety's sake.