The GTA is all about building airguns.
Sorry if you took my reply in a direction I didn't intend it to go.
If you check out several pages of this forum you will find very little discussion about general airgun projects. Most of the posts here are about match results, equipment, techniques, and subjects related only to the airgun benchrest discipline.
I usually go to the Gateway To Airguns forum
http://www.gatewaytoairguns.org to read about and share airgun build information.
The GTA is a wonderful resource where you virtually find an unlimited source of information about building and modifying airguns. I know several hobby machinists on the site.
You will find several posts on the GTA about using barrel liners for airgun barrels.
The GTA has a Daisy Gate as well.
http://www.gatewaytoairguns.org/GTA/index.php?board=186.0 There are several posts in the Daisy Gate about modifying the Daisy 880 with longer barrels, modified hammers, trigger mods, etc. you won't find anything like that here.
Very little content on the GTA is about benchrest match results and equipment.
Another good source for posts about using barrel liners in airguns is the TalonAirGun forum.
http://talonairgun.com/forum/
Both the GTA and TalonAirGun forums have Machinist areas that you may find interesting.
I wish you well with your project but mostly I hope you have fun with it.
Boomer