The only thing that matters to you is WHERE you are shooting FROM. Your perch is everything. Wrong shooting perch, ineffective assassination. Your shooting platform also decides which type of gun you will use. If your target is a mile away, you’d probably want to use a Barret .50 Caliber. On the other hand, if you’re going to be rubbing shoulders with your target, a .38 caliber snub-nose revolver will do. You certainly wouldn’t use the Barrett up close or the .38 at long distance. And you can’t just make a stupid GUESS about from where you will shoot. You must reason out the best spot to shoot from. Since the president is visiting Dallas, you would rightly assume he will pass through Dealey Plaza (the birthplace of Dallas).
You look at Dealey Plaza. Houston Street borders it on the East (the top of the linked photo) and the Triple Overpass on the West (bottom of the photo). Elm Street is the Northern border and Commerce Street is the Southern border (Elm is one-way East to West and Commerce is one-way West to East). It is bisected by Main Street running East/West (top to bottom in the photo). You see it is a mirror image, North/South. You know the president will land at Love Field which is Northwest of Dealey Plaza. So there are a few directions the motorcade may take. However, the president is set to visit the Dallas Trade Mart which is located on the Stemmons Freeway. So, the best direction for him to come would seem to be South on Houston, a shallow right on Elm, under the Triple Overpass, and then off to the Stemmons Freeway. So you get a job at the only business available on the East side of the plaza — the Texas School Book Depository — to position yourself for a shot coming down Houston and turning onto Elm. All other buildings surrounding the plaza are gov’t buildings.
Then you see a problem. If the motorcade comes down Main Street and just keeps on going, the limo will be way out of range of the TSBD. Of course, if the motorcade turns North on Houston you get a shot at the president coming right at you. If the motorcade then turns onto Elm, you’ll get a shot of him going away from you. Sounds good, but Secret Service regulations forbid the presidential limo from making a turn of more than 45 degrees or dropping speed below 45 mph. If the motorcade turned North on Houston from Main and then West on Elm from Houston, they would be committing four separate violations of Secret Service regulations in the space of one city block. You know that ain’t gonna happen and as a lone gunman having to rely on only yourself, you’re not going to count on THAT much luck. So you need to find a perch where you will have the best possible shot whichever direction the motorcade takes.
You look at the Triple Overpass. All three roads converge under it (Elm, Main, and Commerce, North to South). As the convergence comes out the other side, there is a convenient on-ramp to the Stemmons Freeway whether you take Elm or Main. If you place yourself between Elm and Main on the Triple Overpass, you can shift your shooting angle between the two, depending on which way the motorcade comes. It doesn’t matter if they come down Houston and turn onto Elm or come straight down Main (neither of which violates regulations). Even if they DO violate regulations and come down Main, turn on Houston and then on Elm, you STILL get a shot. And the best part of the Triple Overpass is that the presidential limo is coming to YOU! Which means you don’t need a 30-06 or a .308 hunting rifle. The target will be closing toward your position. You can use a less expensive rifle with less powerful ammunition because you’re not having to make the adjustments as the target gets farther away. In case you’re interested, the Mannlicher-Carcano rifle (6.5mm rounds) retailed for just about $20.00, mail order. If the president comes through Dealey Plaza (very likely) and needs to end up at the Dallas Trade Mart, the best place to be to assassinate him is the Triple Overpass.
However, you choose the TSBD because you’re hoping he will come down Houston and turn onto Elm and just chance it that he won’t come down Main. So you setup your “sniper’s nest” on the 6th floor of the TSBD and wait for the motorcade. You see it’s heading West on Main toward the plaza and your heart drops. Then it inexplicably turns onto Houston and then on Elm and you have your shot! How LUCKY can you be?! You counted on the wildest luck to have the Secret Service violate its own regulations and it happened! You take your shot while the limo is practically stopped on Elm and you kill the president. Then your dream is over and ends in complete failure because while headed West on Main Street, the president leans forward towards the driver and says, “Driver, don’t turn right here. Just continue strait through the plaza.”
The only way that Oswald would choose the TSBD is because he was TOLD to be there. He filled out the job application to work at the TSBD just 38 days before the assassination. He KNEW the Secret Service would violate regulations, because that is the kind of “luck” you DON’T count on. He KNEW the route in advance. He HAD to because there is NO REASON that a lone gunman would choose the TSBD if the route could have been Main Street, straight through the plaza, which would screw his shooting solution to hell. The TSBD makes NO SENSE for a lone gunman, reasoning out the best possible shooting position, because it is one of the worst assassination positions possible. While on the other hand, the Triple Overpass is the near perfect shooting perch because it gave him the best shooting position no matter which way the motorcade took. If you get Oswald as the shooter, it’s still a conspiracy.