True cylinder gap on a DA revolver?

Most DA revolvers have a bit of spring tension holding the cylinder at the forward most position.
When the revolver is fired is the true gap with cylinder forward or will physics be pushing cylinder backwards?

Mus408 said:

Most DA revolvers have a bit of spring tension holding the cylinder at the forward most position.
When the revolver is fired is the true gap with cylinder forward or will physics be pushing cylinder backwards?

Click to expand...

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Two issues at work: 1) endshake, and 2) barrel/cylinder gap.
If there is zero endshake, gap stays constant at discharge. If endshake is present, it can be measured with feeler gauges.

Endshake and discharge
At hammer fall, firing pin strikes primer. Cylinder moves forward. Primer ignitions thrusts primer pocket (case) forward, while primer blows back. Power ignition starts bullet forward, cartridge case rearward. Expanding gas pries cylinder gap. Venting gas and bullet recoil thrust cylinder rearward, re-seating primer.
A cylinder with severe endshake may bounce under recoil like a slide hammer. Felt recoil does not begin until the bullet is well downrange.

Endshake may not hurt accuracy, but it doesn't help. The slide-hammer effect may peen standing breech and cylinder ratchet.

Barrel/cylinder gap by itself has no----or nearly no----negative effect on accuracy. Barrel/cylinder gap hurts velocity.
David Bradshaw

Great explanation....Thanks!

"Most DA revolvers have a bit of spring tension holding the cylinder at the forward most position."

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I meant to address this proposition. There is no spring tension (in any DA which I shoot) to load cylinder forward. The CYLINDER PIN SPRING in a Smith & Wesson just pushes the pin into a hole in the STANDING BREECH. At the same time, the cylinder pins pushed the THUMBPIECE rearward. No affect on cylinder.

Ruger DA's work the exact same way, albeit with thumpiece pressed against the frame.

The Colt thumbpiece is pulled rearward to release cylinder. No spring-loading of cylinder.

Charter Arms, High Standard and any of their copies which I don't mess with, unlock with a pull on the ejector rod. Memory doesn't fathom spring pressure loading the cylinder of these contraptions. Before one condemns my perception of these revolvers to arrogance, in my short life I have never discovered time to live with one of these guns. They carry cultural importance; extreme marksmanship requires a more exact instrument.

Correction: the Dan Wesson Arms with INDEPENDENT CRANE LATCH has a spring-loaded ball in the standing breach, which indexes a detent in the extractor star. This loads the cylinder forward. The effect in no way alters the dynamic of combustion pressure firing the cylinder against the standing breech.
David Bradshaw