It's not common and it doesn't work very well.

I've read about the US Navy using a sleeve insert during the 1960's to shoot .308 ammunition in their M1 Garand rifles which normally use .30-06 ammo. The .308 uses the same projectile as .30-06 but the case is shorter hence the sleeve.

Sleeves came out of the rifles at random inconvenient times. Eventually Navy went to the M-14 which is a .308 (7.62 NATO) rifle so no sleeving required. (then they moved on to the M-16)

Semi-auto pistols wouldn't be sleeved but an entire barrel change is very simple. I have a Glock 22 (in .40S&W) that can be converted to 9mm by changing barrel and using different magazines.

Gun stuff isn't all that difficult. You could probably find more than you want to know at http://www.thefiringline.com/forums/index.php
and
http://www.thehighroad.org/index.php
to name just 2 very good "gun boards."