For pretty much all of the handguns on the market today (and for all of the handguns currently being used in competition), the barrel is mounted to the gun in such a way that it sits higher than the shooter’s hand when the gun is gripped in any sort of reasonable firing platform. When the gun is fired, this position gives the gun leverage against the shooter’s hand, and causes the barrel to lift in recoil (if you want a detailed discussion of the physics, let me know – otherwise, just trust me!). This phenomenon, as experienced from the viewpoint of the shooter, is referred to as “flip”.
“Flat” is basically the opposite of “flip”. From the viewpoint of the shooter, the gun appears to lift a relatively small amount. A gun that’s referred to as “flippy” appears to lift a larger amount.
Interestingly, many times, bystanders will think a gun that appears to be flippy from the shooter’s perspective will appear to shoot very flat. This is really an illusion – and actually, the notion of “flat” in the shooter’s mind is also somewhat illusory. The human eye really can’t really accurately follow the full recoil cycle of the gun – the gun cycles in about .05 to .06 seconds (some claim even faster), and the eye only catches a small portion of that (the human eye has the potential to see at approximately 60 frames per second, but in most normal circumstances, we see at about 30 fps – so we catch very little of the actual recoil cycle). Slow motion video actually demonstrates that guns that appear to be flat actually flip quite a bit – but their motion is different from a gun that appears to be flippy. It’s this difference in motion that we’re picking up on as the shooter.
The bystander is frequently reacting to the shooter’s recoil control abilities – for instance, many folks comment on how flat Dave Sevigny’s Glock appears to be, yet photos of him shooting clearly demonstrate the gun is flipping quite a bit. Dave has exceptional recoil control abilities, and the gun returns to point of aim more quickly than the bystander’s eye can follow.
In the end, the gun is almost certainly lifting more than the shooter or the bystander perceive it to be.
Hopefully, that gives you a better idea of what is meant by “flip”… The next time we talk about flip, we’ll talk about whether it’s actually important or not…