Cylinder play, cartridge slop...

S

Sweet Shooter

New member
Couple of quick questions for the enlightened engineer-types among us.

1. My 686 is tight tight tight—no end shake what so ever, none. It has a little bit of rotational play but it feels normal to me. It's almost brand new. But being relatively new to wheelies, how much rotational play is too much, and how does rotational play affect accuracy/round deformation?

2. The cartridges slop back and forth quite freely especially where the recoil shield is flared backward to accept the base pin/ejector star rod-end upon closing. I know/understand that the cartridge case is head-spaced off the rim. but what actually happens when the round detonates? I've seen graphics diagrammatic animations of what happens when a bottleneck rifle ctg goes off, but nothing that shows what the sequence of events is in a revolver with a straight wall/taper 357mag case. For example does the frame/top-strap take the brunt of force or should the cartridge seal against and adhere to the chamber walls? My chamber walls are literally like mirrors and would not provide much of a "key" for the soft brass. Should I let them build carbon to help provide a key?

What say you?

-SS-

Edit: change "Cylinder walls" to "Chamber walls".
 
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:D What say ME?!
I say, "Well, have you SHOT this revolver?!"

Everything sounds normal, and kind of sounds like you are worrying about something that needs no worrying whatsoever.

My 686 is a dash-3 variant, 1989 production. It would be described just about exactly as you described yours, with regards to all the details you mentioned. It runs perfectly and always has. Hopefully, always will.
 
Do Not Shoot That Gun!
It's too dangerous.
Send it directly to me, as soon as possible, for a through check.
Did I happen to mention that we are moving soon with no forwarding address?
 
Well, now that you ask:

In a revolver, as the primer explodes, the force drives the primer backward against the breech face. Then as pressure builds up inside the case, the pressure drives the case backwards against the breech face, reseating the primer. Then pressure dissipates, the cartridge case relaxes a little, and sort of reseats itself.

If pressure is near excessive, the primer will sort of flow around the firing pin, even flattening out to some extent. This is usually accompanied by a swolen case that is sticky, or difficult to extract.

Bob Wright
 
Since the head (which is the rear end, odd as that sounds) of the cartridge case impacts the recoil shield, it tries to push that part of the frame backward. That, in turn, tries to bend the frame and stretch the top strap. In normal use, the parts are strong enough to resist that force and the revolver functions normally. If a gun is weak, or if a cartridge has an overcharge of powder, the frame or topstrap can be overstressed and fail, but that rarely happens unless someone either overloads for an old, weak gun, or tries to "soup up" a cartridge beyond what the gun can handle.

Jim
 
On rotational play, most modern revolvers like the S&W, Ruger, Dan Wesson, and later Colt's like the Mark III, Mark V, King Cobra etc. are specifically designed to allow the cylinder some rotational movement.

Rotational movement with the action un-cocked, OR COCKED AND THE TRIGGER HELD BACK is normal and REQUIRED.
The purpose is so the slightly loose cylinder will allow the chamber to align itself with the bore.
How much rotational movement is present has no specification. What matters is: is the revolver accurate? Does the revolver spit bullet metal.
If it's accurate and isn't spitting bullet metal out the barrel-cylinder gap, it's in proper working order.

Only the old Colt action as used on guns like the Detective Special and Python lock the cylinder tightly when the trigger is pulled.
Pulling the trigger and holding it while you check for cylinder movement in a S&W or other brand IS NOT A VALID TEST for anything.
Even if a S&W or other brand seems to lock up tightly when the trigger is pulled, there's still enough backlash built into the action to allow the necessary movement of the cylinder.

So, in order to operate correctly your gun must have free movement of the cylinder, and how much movement is not an issue as long as it works properly.

When the revolver is fired, the actual recoil shield, which is the circular area around the fining pin hole is what takes the impact, and the gun is designed to be strong enough to absorb the pressure of the ignition and firing force.

No matter how smooth chamber walls are, brass cartridge cases still expand and adhere to the chamber walls for the instant it takes for the pressure to drop to safe levels.
It's the adhesion to the chamber walls that keep the forces in the safe range for the action.
This is why you never oil cartridge cases or fire a gun with oil in the chamber.
The oil will form a barrier between the case and the chamber and will prevent the case from adhering for that instant.
When oil is present and adhesion can't take place, the case is allowed to slide backward, greatly increasing thrust against the recoil surface.

So it's a combination of the strength of the frame of the revolver and the brief adhesion and sealing of the chamber by the case that allows the gun to handle the forces.
 
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