I recently sent them an E-mail asking if it was possible to retrofit a newer, thicker barrel to an older Mini-14.

Here's their response:

"Comment / question:

Is it possible to have a new, heavy-tapered barrel retrofitted to my 185 series mini-14 which has the original pencil barrel?

Response:
It's more cost effective to replace the firearm with a new one. The new flanged style barrel would also include changing the gas block and slide. You may send you firearm into our NH facility, and we will offer to replace it with a new model at a discounted price. Please contact us at 336-949-5200  for further information. Thank you for your email.

If you need further information, please visit our website at www.ruger.com or contact us at:

Revolvers, shotguns, rifles, 10/22 Charger Pistol:  (603) 865-2442
Pistols:  (928) 778-6555
Serial Number History Information:  (603) 865-2424

Please note:  This e-mail is sent from a notification-only address that cannot accept incoming e-mail.  Please do not reply to this message.

Sincerely,
Ruger Firearms"

I called the number above, gave them my Mini's serial number, and was told I would have to get an RMA and return the rifle to them.  They would evaluate it, and quote me a price on a new Mini.  I don't know if there is any choice in models, but I would assume so.

I realize this is quite a bit like buying a pig in a poke, but I had no idea this was even an option till now.  My Mini shoots 2 MOA, so I've no interest in taking the offer, but some folks might want to take a chance.  FWIW, it appears that most Minis are selling for about $300 or so below MSRP at this point.  I assume Ruger will discount off the MSRP, not street price.

Obviously, remove any non-Ruger accessories before sending it in, and sell them off, as they probably won't fit the new Mini; The accessories might not even be needed on the new Mini.

If anyone goes this route, please report back with your findings.

Yes, some or all of those fees/taxes might apply.  Some might not.  Good point.

On the face of it, that would make sense for most guns.  Given these are Mini-14s we're talking about, and given their reputation for inaccuracy, that's a different thing.   I know not all Minis are inaccurate, but some bad apples have spoiled the barrel.  I don't know how one would fare selling a used, older Mini on this site.