Can I fly with a stripped M1911 frame and a stripped revolver frame in my check on baggage?
or even for that matter priority mail those frames to myself?
"check on?" Is that a new hybrid between "checked" and "carry on?"
All gun parts are required to be in checked luggage. Terrorists have tried assembling a bomb aboard an aircraft from innocuous items carried on by several people working together -- hence the water bottle and 4 oz restrictions for anything that might resemble an explosive ingredient. Trying to get the parts of a working gun onboard in several people's carry-ons wouldn't be any different.
Stripped or not, if it's classified by the ATF as a firearm, you should treat it as such. In this case, the frames are handguns for all intents and purposes even if stripped, legally speaking.
If you mail a handgun across state lines, you need to use an FFL -- either to send or receive.
Side note -- probably not applicable in this case:
Only an FFL can use USPS to ship a handgun. Even if you're sending your handgun to an FFL, a manufacturer, or any other licensee, you have to use a "common carrier" such as FedEx, UPS, etc.
You also need to look at the USPS regs if you want to use them. In my case, since a stripped AR receiver can be completed as a pistol, they treat it as a pistol since there is no barrel. By definition, a long gun needs a 16" barrel minimum. Without a barrel (and attached upper), the lower receiver is classified as a handgun by default according to USPS definitions, and it must be shipped by an FFL to use USPS. Since FedEX and UPS are super expensive, I found it's cheaper to pay an FFL to ship it USPS. 
Firearms mailed via USPS have to include services that include signature capture and tracking. Regular priority mail won't be enough.
https://pe.usps.com/text/pub52/pub52c4_009.htm
Since the frame resembles a handgun, you'd need to do the "locked case and declaration" just like a working handgun.
Check your airlines' rules. This is from United:
The regulations below refer to all firearms (or items that may resemble a firearm),
including airsoft guns, BB guns, paintball guns and any antique trophy guns or weapons.
https://www.united.com/ual/en/us/fly/travel/baggage/sports-equipment.htmlEven though it's not functional, the airline sees it as a firearm. If they handle replicas, BB guns, and paintball guns as firearms, a stripped firearm receiver -- a firearm by ATF definition -- would also qualify.
On top of that, ask yourself if you'd want the frames to be stolen. Without the added protection of a hard-sided, locked container, they could easily go missing. The airline would probably not be very accommodating if you reported as stolen undeclared firearms.
These are my understandings based on personal experience and research. As always, it's easier to make your flight by being over-prepared than hoping your interpretation is the same as the airlines'.
