justindad
01-08-2024, 11:28 PM
I have a 3” DAO Kimber K6S and I have experienced the cylinder lock up twice, each after about 400 rounds were fired over the course of a year.
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The first time I had the cylinder lock up, I was firing 158 grain boolits over a max charge of AA#9. The recoil was heavier than max charges of HS-6 and Enforcer, and the velocity was greater as well. I took the gun apart and found that the factory assembled the gun with a white grease which had since dried up completely. I figured the dried paste could cause the clock work to lock up, so I cleaned it out and went on with life. The gun worked great and the trigger was smoother than ever.
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The second time the gun locked up I was shooting 180 grain boolits with HS-6 and Enforcer, both just a tad over starting charge. Velocities confirmed the charges were relatively light, but the recoil was stiffer than anything I shot in this gun before. My hand didn’t hurt, it was more of a numbing sensation. That recoil was hitting hard with wooden grips. So I took the gun apart again. The clockwork had powder and maybe metal dust debris inside (the gun is still breaking in). I am ~25% done cleaning it and I think I found the real reason why the cylinder locks up: if the cylinder is just a bit further forward and if the pin on the back of the cylinder is a bit more eccentric to the cylinder release pin, then the trigger acts as if the cylinder is wide open, forbidding trigger movement.
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The pin circled here is what I called the “cylinder release pin” above. When you push the cylinder release door, this pin pushes into the spring-loaded cylinder pin, allowing you to open the cylinder.
321903
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Here you can see an arm attached to the trigger, which cannot raise up when the cylinder is open. Here the trigger is locked, and I believe the trigger arm hits this same cylinder lock when the dreaded cylinder lock-up occurs.
321905
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Here we can see that the cylinder pin pushes the cylinder release pin into the frame by 0.098”.
321910
321909
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Here we can see that 0.098” does not push the cylinder release pin in very far. To put it in a simple way, I’ll say that the cylinder release pin should move somewhere closer to 0.15” in order to maintain adequate clearance between these two parts during the firing sequence.
321908
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Here I am using a nylon pick to show the cylinder lock moved away from the trigger arm, as is the case when the gun is assembled and the cylinder is closed.
321911
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Here we can see that the cylinder release pin has a lot of clearance with the hole in the frame. Note that the cylinder pin has a ball end, so when these two are eccentric the cylinder pin does not push the cylinder release pin as far into the frame as it does when the two are concentric. I imagine heavy recoil could force the eccentricity into a maximum condition.
321912
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So what can Kimber do to fix this cylinder lock up?
1) Make a tighter fit between the cylinder release pin and the frame, so that the cylinder pin and the cylinder release pin are held concentric to one another. They could add a bushing, just like the firing pin has a bushing. This would have the added benefit of making it more difficult for debris to enter the clockwork chamber.
2) Add a chamfer to the upper/rear corner of the trigger arm. This would provide more clearance with the cylinder lock, in a way that is much better than the 0.15” extension I mentioned above (which was just for illustration).
3) Make it feasible for customers to clean the spring loaded pin inside the cylinder. If it gets too dirty in there, the pin can get stuck inside the cylinder.
4) Don’t assemble revolvers at the factory with grease in the clockwork.
*
The first time I had the cylinder lock up, I was firing 158 grain boolits over a max charge of AA#9. The recoil was heavier than max charges of HS-6 and Enforcer, and the velocity was greater as well. I took the gun apart and found that the factory assembled the gun with a white grease which had since dried up completely. I figured the dried paste could cause the clock work to lock up, so I cleaned it out and went on with life. The gun worked great and the trigger was smoother than ever.
*
The second time the gun locked up I was shooting 180 grain boolits with HS-6 and Enforcer, both just a tad over starting charge. Velocities confirmed the charges were relatively light, but the recoil was stiffer than anything I shot in this gun before. My hand didn’t hurt, it was more of a numbing sensation. That recoil was hitting hard with wooden grips. So I took the gun apart again. The clockwork had powder and maybe metal dust debris inside (the gun is still breaking in). I am ~25% done cleaning it and I think I found the real reason why the cylinder locks up: if the cylinder is just a bit further forward and if the pin on the back of the cylinder is a bit more eccentric to the cylinder release pin, then the trigger acts as if the cylinder is wide open, forbidding trigger movement.
*
The pin circled here is what I called the “cylinder release pin” above. When you push the cylinder release door, this pin pushes into the spring-loaded cylinder pin, allowing you to open the cylinder.
321903
*
Here you can see an arm attached to the trigger, which cannot raise up when the cylinder is open. Here the trigger is locked, and I believe the trigger arm hits this same cylinder lock when the dreaded cylinder lock-up occurs.
321905
*
Here we can see that the cylinder pin pushes the cylinder release pin into the frame by 0.098”.
321910
321909
*
Here we can see that 0.098” does not push the cylinder release pin in very far. To put it in a simple way, I’ll say that the cylinder release pin should move somewhere closer to 0.15” in order to maintain adequate clearance between these two parts during the firing sequence.
321908
*
Here I am using a nylon pick to show the cylinder lock moved away from the trigger arm, as is the case when the gun is assembled and the cylinder is closed.
321911
*
Here we can see that the cylinder release pin has a lot of clearance with the hole in the frame. Note that the cylinder pin has a ball end, so when these two are eccentric the cylinder pin does not push the cylinder release pin as far into the frame as it does when the two are concentric. I imagine heavy recoil could force the eccentricity into a maximum condition.
321912
*
So what can Kimber do to fix this cylinder lock up?
1) Make a tighter fit between the cylinder release pin and the frame, so that the cylinder pin and the cylinder release pin are held concentric to one another. They could add a bushing, just like the firing pin has a bushing. This would have the added benefit of making it more difficult for debris to enter the clockwork chamber.
2) Add a chamfer to the upper/rear corner of the trigger arm. This would provide more clearance with the cylinder lock, in a way that is much better than the 0.15” extension I mentioned above (which was just for illustration).
3) Make it feasible for customers to clean the spring loaded pin inside the cylinder. If it gets too dirty in there, the pin can get stuck inside the cylinder.
4) Don’t assemble revolvers at the factory with grease in the clockwork.