Let’s start by acknowledging we can minimize our search by ignoring all cartridges within each caliber that don’t produce maximum velocity in that caliber. In other words, the 223 Remington throws the same bullets as the 220 Swift, but can’t approach its maximum velocity, so there’s no chance it can shoot as flat. Ditto the 6.5 Creedmoor and 6.5-300 Wby. Mag. etc.
This means we can first determine the fastest cartridge in each caliber, then compare it against the fastest in others. The caveat here is that “fastest” becomes a bit murky. Do we compare the fastest factory loads or top end handloads from select handloading manuals? And is it fair to include Risky Ralph’s overstuffed, compressed-powder loads that exceed the highest handloading guide’s top loads by 400 fps and leave primers looking as if they’d been squashed on a train track? Heck, I can’t even find agreement on maximum muzzle velocities in handloading manuals from Speer, Hornady, Nosler, Berger, Swift, Hodgdon, Norma, Sierra, Barnes… Furthermore, just because the manual lists those speeds does not mean your rifle will deliver them. Every rifle is different. Top muzzle velocities with the same combination of powder, primer, and bullet can vary by 100 to 200 fps. Trust but verify.
What I’ve done with this deep dive review is use the highest Handloading Manual velocities I’ve discovered, trusting that you, gentle reader, will understand that your mileage may vary.
Caliber by Caliber
Choosing the flattest shooting rifle cartridge in each caliber category seems fair, fun, and revealing, so we’ll do that before identifying the all time top dog. Below is the information I’ve gleaned from 17-caliber through 338. I stopped there because few hunters are going to tolerate the recoil or rifle weight needed to operate a flat shooter above 338-caliber. I have not identified bullet make and type because that doesn’t change impact drop. Only B.C. and MV do. Be aware that many of these bullets could have been target bullets. Appropriate hunting bullets may not reach these levels of B.C. Also know that not all manufacturer-claimed B.C. numbers are accurate. Often they’re inflated. And they can change in your rifle and will change at different velocities. during their trips downrange. Also, I used something called G1 B.C. numbers which are not quite as accurate as G7 numbers in predicting trajectories of today’s wildly long, sleek bullets. Still, by using G1 across the board, we are on a level playing field. The good news is that these bullets might shoot even a tad flatter than these numbers indicate.
All the following data was computer generated as if all loads were fired from a (simulated) dead flat (level) barrel, so these are pure drops. Zeroing for 100 yards or farther will change drop significantly. Barrel length will change MV. So don’t assume that you’ll be shooting the world’s flattest rifle cartridge and bullet until you’ve verified your MV and bullet B.C. I’ve included different bullet weights/BCs for most rounds to illustrate how BC changes drop at longer ranges. Here we go!
Flattest Shooting Rifle Cartridges by Caliber — Ron Spomer Outdoors is written by Ron Spomer for www.ronspomeroutdoors.com