casca1,
I've been researching your question, going through all the stuff I have - I can not find reference that the TOPPER JR 490 was ever offered with .30-30 Win barrel
?
What I've found is that model was in production from 1961 to 1983 and saw 4 variations during that time. The only chamberings listed are 20 ga. 2 3/4", .410 bore 3" - 1st Variation; then in 1970 20 ga 3" and .410 3" (2nd through fourth variations - 1970 thru 1983) and the addition of a 28 ga 2 3/4" offering during the 4th Var. 1976-1983.
It's probable that a former owner had a rifle barrel fitted to the 490 frame. I'd be cautious with that combination as H&R issued warning that the shotgun frames were not necessarily strong enough to handle rifle chamber pressures?