There's a Rem 788 in .243Win in a shop 1:30 drive from my home. I knew it is a
multi-rear-lug affair. Then I read some about the rifle and I found the receiver
not being cut as much as, say, a Rem 700. I was wondering if this type of action
can be build into an accurate rifle, say, 1/2 MOA with heavy barrel, in 22-250?

You are correct. The 788 action is stiffer than the 700 action due to less metal removal. If you can find a good adjustable trigger for it , I see no reason why it wouldn't work. Remember, each caliber 788 had a custom made magazine and follower for that caliber only! Since you are talking about converting to .243 you may not have any problems since both cases have similar lengths in the body. You might try feeding a 22-250 in it to be sure.

I bought a used 788 as a truck gun years ago in 22-250 and was surprised by it. Mine has been abused by most standards and still shoots pretty well. The one thing I was cautioned about by a gunsmith who reworked the trigger was that rear locking lugs like this don't take as much pressure without binding the bolt. I have used some hot loads but have never had it stick either so I'm not sure. It is a very stiff action. The smith I took mine to adjusted the trigger and silver soldered the case. I haven't touched it since and have had no regrets. This is my grab it and go gun and it has been spray painted with bow paint and generally abused. It's due for a new barrel now but at one point it would stack them up. If it's a good deal I'd buy another one. Make sure it comes with a magazine, sometimes they're hard to find.

Thanks for you both, I would seriously consider the project.

788's make great hunting rifles. I own four of them and each is a very accurate gun. Canjar makes an adjustable set trigger, but expect a long wait and you will pay for it, $180 US when I got my last one. Beautiful triggers though. Apparently a gentleman by the name of George Stringer in Earlington, Kentucky modifies these triggers to make them adjustable. I haven't tried one yet, but I have a spare coming and when it gets here I'm going to ship one off to him and we'll see. His phone # is 270 383 3346 and his email is gunsmith@spis.net - Dan