This guy on redditor Oelund brought a new high speed camera to the range to see how it was compared to his older one, he figured it would be cool to film the recoil booster in a .22LR Colt ACE, since he was quite fascinated about the recoil pattern of it when he recorded it with his old camera some time ago.
1. The Colt ACE Service Model .22LR
The Colt ACE was developed in the 30’ies as a cheaper training pistol for the .45 ACP Colt 1911. The kit consists of a new slide (almost identical to the .45 slide, except with a different firing pin and extractor), a new magazine, and a barrel with a separate ejector and a floating chamber. It was available as a conversion kit as well as stand alone pistol.
The heart of the ACE is it’s free floating chamber, developed by David Marshall Williams. The reason for this floating chamber is to boost the recoil of the weak .22LR cartridge to allow it to cycle the heavy steel slide of the 1911 pistol.
The floating chamber is essentially a short stroke gas piston. As the bullet travels down the barrel the propellant enters a small chamber right in front of the piston. The expanding gasses then push the barrel and the chamber away from each other, giving the slide the extra boost it needs to cycle. Williams used a similar system on other .22LR trainer guns, including rifles and machineguns. This recoil booster gives the pistol a rather interesting recoil.
This is an older high speed recording (1000 frames per second) from my old camera (Casio Exilim EX-ZR200). The lighting conditions were not optimal, but the recording did show something quite interesting. Notice how the pistol is pushed forward initially after the shot is fired. This is because the chamber and barrel is pushed away from each other. This pushes the barrel (and pistol) forward against the weight of the slide for a couple of milliseconds before the rearward recoil of the slide takes over.
I got the opportunity to test out a new and slightly better high speed camera (Nikon1 J4), and I figured this would be a good subject to investigate further. This is recorded at 1200 frames per second, so it’s not that much faster. But the quality is definitely an improvement. In this clip you can see the floating chamber kicking the slide backwards. It is also very clear that the booster kicks the barrel forward causing it to dive down before the recoil takes over.
Here is another angle. The barrel dive is very clear here. Another thing that is interesting to note is the inertia of the firing pin as the slide slams forward.
Here is a closer view of the floating chamber. It is easy to see how the chamber functions like a gas piston.
An even closer view of the stroke. As you can see it provides a very violent and explosive kick that looks almost instantaneous even when recorded at 1200 frames per second.