Taurus M94 - endshake questions

[killertom]

Dear Members,

This is my first post here, so please bare with me. I have a .22 Taurus Model 94, it is about 15 years old. The cylinder gap is normally right around .004" which is pretty good. However it has a bit of endshake. If I push the cylinder to the rear the gap will increase to .009". If I release the cylinder it returns to its forward position with the .004" gap.

My question would be, does this gun need any kind of servicing? Or is it fine as it is?

Thanks,

Tom

 

[unspellable]

taurus end shake

I'm going to go out on a limb here. This is not an expensive revolver. The 22 LR is not going to slam the cylinder back and forth like a 44 Magnum. Taurus does not have a wonderful reputation for their service. My inclination would be to run with it as is unless you have other symptoms.

Other symptoms would include possible misfires do to excess head space. (Not to be confused with ammunition caused misfires, quite common in some varieties of 22 LR.) Another possible symptom would be short carry up which can also be caused by ratchet and hand problems. A third symptom would be spitting crap out the cylinder gap. (I ran some tests with an adjustable cylinder gap on a 44 Mag. It started spitting crap at a 0.012 gap.)

 

[killertom]

Thanks for the reply!

Apart from this endshake thing the revolver is good, timing is perfect, lockup is a bit loose on some chambers but its not spitting lead so I'm ok with it. You did mention something however that made me think. So is it possible that when firing the recoil from the ammo moves the cylinder to the rear, effectively creating a .009 cylinder gap? I'm guessing that the firing pin pushes the cylinder forward, and also the cartridge base being rimfire swells some too during firing and also pushes the cylinder forward somewhat. Am I about right in assuming this?

Thanks,
Tom

 

[unspellable]

Cylinder movement

The cylinder movement is a good bit more complex than you might think. It also varies a bit depending on the particualr revolver design.

I'm going to start with a S&W chambered for a center fire cartridge. At rest, the cylinder is held in the forward position by spring tension. When thwe firng pin hits the primer it pushes the cartridge to the forward limit of the head space. It then dents the primer. When the primer detonates it moves to the rear out of the primer pocret. There is a very short high pressure spike in the chamber caused by the primer. The pressure drops and then begins a slower rise again as the powder begins to burn. The pressure begins to move the bullet forward which tends to drag the cylinder forward with it. (But it's already at the forward limit. At the same time the case is pushed to the rear, reseating the primer. Also at the same time the frame begins to stretch. The pressure peaks (For most loads) as the bullet goes through the forcing cone. Whenthe pressure drops, the frame springs back ,shoving the cylinder to the rear where it bounces off the recoil shield, runs forward and bounces of the forward limit. In the case of the S&W this is the bottom of the cylinder well hitting the tail of the yoke. It's this latter bouncing back and forth that contributes to end shake over the course of time.

in the case of a Ruger Blackhawk the forward travel is limited by the cylinder neck against the front of the frame window. It has a much larger bearing surface than the S&W yoke tail and is the primary reason the Blackhawk will stand up to abusively havy loads better than the S&W. (Pressure has nothing to do with it, other than you have to have pressure to make things happen.)

The 22 will not differ from the centerfire much in nature, but the avaergae center fire will stir up a good bit more slam and bang. If I recall correctly, the Taurus cylinder is held forward under spring tension like the S&W. I think its forward travel is limited by the cylinder neck bearing on the yoke collar.

I hadn't thought about the rim on a rimfire expanding, but I'd suppose it does, and then gets reformed like reseating the primer in a center fire if the various clearances arfe right.

Note that the frame springs back to its original dimensions. End shake is due to battering on the bearing points, NOT permanent frame stretch.

 

[killertom]

Wow, thanks! Great information!

"The 22 will not differ from the centerfire much in nature, but the avaergae center fire will stir up a good bit more slam and bang. If I recall correctly, the Taurus cylinder is held forward under spring tension like the S&W. I think its forward travel is limited by the cylinder neck bearing on the yoke collar."

You're perfectly right, the Taurus is an exact copy of the S&W mechanism. So I'm guessing this whole endshake thing is not such a big deal on a .22? Its not likely that the pressure generated by the .22 ammo would push back the cylinder and widen the cylinder gap?

Thank you,

Tom

 

[1911Tuner]

End shake is due to battering on the bearing points, NOT permanent frame stretch.

Yet, it's been proven that they do stretch permanently with enough use. Bolt-action rifles...semi-auto pistol slides between the breechface and the first lug...and revolver topstraps.

Back in the 80s when I was badly envenomated by the Metallic Silhouette bug, I shot two Ruger Super Blackhawks loose in a period of about 3 years. I sent them back to Ruger for a tune-up. Only one was viable, and they notified me that the best at they could do about the other was to sell me a replacement at their cost. The reason given was that the frame was stretched beyond repairable limits as determined by their gauges. They also strongly advised me to refrain from using any more handloaded ammunition in the gun that was repaired...even though no mention was made of it in our correspendence.

So...Revolver frames can and do stretch...permanently...and Super Blackhawks aren't really indestructible.

 

[unspellable]

stretch

Frames (be they revolver frames or bolt action frames) DON'T stretch unless they have been badly abused. (You will note Ruger told you to stop using handloads even though you didn't mention them, they have some idea of how things work.)

It's basic mechanical engineering or materials science 101. If you apply a force to a piece of steel, it will deform. Remove the force and it will return to its original dimension. Unless you deform it past the elastic limit and then it will take a set. Once it does so it has been seriously weakened. Think of the valve springs in a car. In one minute they are flexed more times than the average revolver will be in a lifetime. They rarely give any trouble.

To actually literally stretch that Ruger frame you would have had to apply a force more than twice what it was designed to take with a proof load. Actually the frame is considerably stronger than even that. When a revolver is blown apart by a serious overload, it's generally the cylinder that fails. (When you see those pictures of blow revolvers, it's the cylinder that failed. The flying scrap metal will hit the top strap and shear it. It didn't fail by stretching

End shake develops at yoke tail and such because a large force is applied to a very small area and can exceed the yield point in that small area.