Remington and Savage are 1/4-28. Winchester used 1/4-32 I believe. I don't know about the others.
If you go to the hardware store and ask for 1/4" fine thread you'll get 1/4-28 which will fit remington and savage. That's the way I made my headless bedding screws, I bought some long ones and cut the heads off. Beats paying brownell prices.
103, if you have a bolt/screw wholesaler in your area, take the action screws to them and they can match with black or stainless. I always replace mine with Allen head and like Gary bought long screws for bedding there also. Good luck
If you have a gun made across the Pacific or Atlanta chances are the have METRIC Mortar Forker screws. On a new CZ 457 I even had to get a metric set of Allen wrenches to take the barrel out of the action. Ace Hardware usually has many screws and bolts in Yankee and Metric, carbon steel and stainless. Fasten All also has a pretty good selection of bolts and screws. Take the screws with you and fit each one. I have bought long bolts with only threads near the end. Then cut the head off and smooth and then shorten the threaded part till no threads show when screwed in the action. Makes good fit screws for stock making and glass bedding. Good Luck