H&R makes several different receivers, capable of various pressures.
Centerfire rifles use an SB2 receiver that can be fitted with both rifle and shotguns barrels (except 10 ga).
Shotguns have an SB1 receiver. Shotgun barrels (410-12 ga) can be fitted to it.
Some of the lower pressure rifle calibers and pistol calibers can be fitted to it; .357 mag, 44 mag, 30/30.
Barrel fitting is up to about $ 150 with parts labor and shipping.
When you switch barrels, you have to re-sight your rifle in.
The Handi-rifle gurus are all on the Greybeard Outdoors forum, and a lot of the more seasoned guys have given up on switching barrels.
Switching shotgun barrels is no big deal.
You can buy a used barrel in the Greybeard H&R classifieds for about $70.
I have bought and sold a few myself, but am now "handi-less".
Go to www.hr1871.com
to customer service or barrel accessory program for an order form with prices.