Keep your Mdl M70, but send the Rossi back to Brazatech in Tampa for warranty work. I agree with Bountyhunter's clues (good job, B-h!) and can think of only a couple of others, but otoh, why not give them a chance to fix it? They really had a great customer service reputation in the past - I was proxying for my sister on an older (abused) 22 pump rifle and they really came through.

So far my only concern is dinging the rimfire barrel with that centerfire firing pin (yeees... it already happened with an accidental dry fire... but subsequently it fires just fine into the sand-filled weapons discharge bucke - actually, the firing pin on this example has some real authority)

I have an older (Russian, I think) side-by-side that has one chamber just a wee bit deep - a matter of a few thousandths - and that barrel will only reliably fire with new shotshells - fire one and reload the hull, and it has about a 20% misfire rate. New hulls, factory ammo - perfect. The other barrel fires everything chambered in it flawlessly, as one would expect. I might make a firing pin for that one some day... nah!