The Williams Floating Chamber

Yesterday, I mentioned shooting some .22 CB Shorts in my Remington 550-1. The rifle is designed to feed .22 Shorts, Longs, and Long Rifles interchangeably. The mass of the bolt and the strength of the mainspring are balanced for .22 LR, so in order to feed .22 Shorts as a semi auto, they need a boost.

This is accomplished by the inclusion of a Williams floating chamber in the breech end of the barrel. When installed and shooting .22 Longs or LRs, the seam between the end of the floating chamber and the rest of the barrel is sealed by the cartridge case. However, it's uncovered when shooting Shorts, so some of the gas from the cartridge goes into the gap and floats the chamber, allowing it to recoil a short distance, giving additional impetus to the bolt. If you go over to Numrich Arms' website and look at their exploded diagram of a Remington 550-1, the floating chamber is part #50.

I thought it would be a good idea to give my Remington a thorough cleaning, since I'd never removed the floating chamber, and since I bought it about 2.5 years ago it's seen close to 1,000 rounds through it, including 60 or so CB Shorts yesterday. It was filthy inside. After I got the floating chamber out and cleaned up I took some pics, here are a couple that came out halfway decent.

There was a fair amount of lead buildup on the shoulder of the piece, which I was able to scrape off with a small screwdriver.

Before being used in the Remington 550, the Williams floating chamber was used in the Colt Ace and .22 conversion kits, which were designed to mimic the recoil of a M1911 in .45 ACP.

It's a really clever solution to a couple interesting engineering task: make a semi auto that can feed .22 S, L. or LR interchangeably, and make a .22 pistol recoil more like a .45.