You could certainly bud now. Then in a few weeks break, bend over, and half detach the callery stem well above the bud to force the bud. When the bud is growing well (6-inches?) then cut off the rootstock stem above the scion growth.

This suitability for budding probably suggests that grafting would work too, but I have no experience with late grafting).

Since Bradford pears are cheap to purchase, it sure would be easier to buy the biggest ones that you can and graft them at home. The potted root system will also save a year or more over having to re-grow the chopped-up,field-grown root system that you are tempted to steal from someone else's property. As in....I just noticed some stacks of money at a place nearby , and I was wondering if I could .......

copingwithclay. That was being RUDE. I know Texans aren't like that. The Bradfords are a good idea, though.
Bill

"tempted to steal from someone else's property"
1: I have the owners permission, maybe I should have mentioned that.
2: These are wild seedlings of Bradfords that have gone feral and invasive. Literally hundreds of seedlings in about 500 sq ft'
3: I would want to graft onto pencil sized seedlings not "the biggest tree I can afford"
4: I don't steal.

I sometimes pick up "Bradfords" in 3-4 gallon pots at the end of the season for just such use. A couple months ago I saw some that are $19 normally, marked down to $5, and when rung up the were dropped to $2.50! I got the best three.

But back to Callery seedlings. Digging them up anywhere is doing the property owner a favor. They are now weeds (and fireblight reservoirs I have read).

Also, when I said you can bud "now" I really meant this spring season. The bark has to slip and that may still be a few weeks.

I wish that every law-abiding friend would be non-supportive when hearing their friend's plans to take someone else's property, and would offer an alternative plan to achieve the real goal w/o the 'stealing' part. Thanks for the clarifying info. Good for you.....On the grafting strategy, I have grafted on many big and small Bradford branches with various pear varieties using T-bud, bark, and cleft grafts. I wish that every kind of fruit tree was as cooperative as pears. A great grafter here uses a single pear T-bud on the upper area of the central leader on several-year-old Bradfords when converting them to fruiting pears. He says that the emerging shoot will develop into all the upward growing,symmetric branches of the tree's future top. Instead of starting with only 1 bud, I prefer starting with a bark graft also at the upper central leader, the scion having at least 3 buds. We both clip off all the existing unwanted branches so the scion/T-bud can get all the sap.As long as you can see the pear trees currently growing new flowers/leaves/stems, you should find that the bark is slipping and thus ready for T-budding (or bark grafting).Even in summer.Even in hot August. After the trees have been enjoying some rain and the nitrogen that I imagine must be in the drops, they may start a flush of new growth. Time to graft again. When I have grafted pears in 95 degree August, I sure wanted to provide Sun protection for the fragile Parafilm that the scions were pre-wrapped with. I used scissor-cut 5" X 10"strips of thin, white plastic grocery bags to form a Sun shield/ humidity enhancer by Skotchtaping the 10" sides into a long seam and the folding and taping one end into a cul-de-sac. After slipping the loose 'tent' over the scion, I used a single verticle strip of the tape to hold the tent in place so wind would not blow it away.Enough light penetrates that plastic that new tiny leaves can photosynthesize. Once the leaves are big enough to push against the tent sides, the tent comes off for good. When doing paw paw grafting in the same heat, I replace the outgrown tent with yet a bigger tent until the paw paw leaves are bigger........Good luck with your great idea in converting those pears into a very useful source of good eating.