1st time hunting

If my poor memory serves me the Winchester 140 model falls into their Ranger line. These were fairly inexpensive shotguns for their time. The reports are not very good on them. If you have a sound working model I see no reason not to use it. Depending on your physical size, a full sized 20 ga shotgun does not kick with much authority even in 3". Hopefully it has a rifled barrel if not then your shootable deer distance is about 50-60 yds. You will have to see where it prints slugs on targets to see what kind of groups it will shoot. I would start at 25 yds with a good sound background and a 3X3 feet sheet of cardboard. Purchase a couple boxes of different rifled slugs, if the barrel isn't rifled, and see which ones give you the best group. If the barrel is rifled, then purchase a couple boxes of saboted slugs and again see which one gives the best group. The 140 models had some weak spring issues and hopefully yours is trouble free. Good luck and happy hunting.