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My understanding is that the lockup on most DA revolvers can be checked by thumbing the hammer back to the SA position and trying to rotate the cylinder and wiggle it back and forth. The tighter the lockup the less movement.

I recently became aware that the old style Colt DA lockwork has to be judged differently. The hammer has to be thumbed back to SA and held there while the trigger is pulled and held back. Only then is the final lockup achieved. Is this correct?

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on colt d/a`s from 1905-1968 the hand supplements the lock up by a slight travel past bolt lock{ that is why a gun slow in time will jump in time at the last instant}this holds the cly hard against the bolt at the instant of fireing. since the cyl also opens to the left this also try`s to hold the cyl shut.this in turn produces the tight lock up and general better accuracy colt is famous for. you should have zero movement with the hammer down and trigger held to rear{ lower hammer gently}. /forums/images/graemlins/cool.gif
 

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Re: Q on Old Colt Lock work

The older Colt action works entirely different than most all other brands of revolvers.

The Colt is intended to lock the cylinder immovably in PERFECT alignment with the bore.
This is Colt's famous "Bank Vault" lockup.

At the moment of ignition, the trigger is all the way back and the hand forces the cylinder into tight lock up with no free cylinder movement at all.

With the chamber closely aligned with the bore, the bullet enters the barrel with no distortion.
This is one reason for the Colt's generally superior accuracy over other brands.

All other modern revolvers work in an entirely different way.
In these revolvers the cylinder is allowed to be slightly loose at ignition, by design.
This free movement allows the cylinder to align itself with the bore when the bullet passes from the chamber into the barrel.

The problem here, is that since the bullet isn't in perfect alignment, it strikes the barrel off center, which causes some deformation of the bullet, which degrades accuracy.

The big advantage of the Colt system is better consistent accuracy.

The down side is, the action must be hand fitted at the factory, and this increases the cost to the point of being uneconomical to produce.

Second, the action must be in perfect adjustment and timing to work properly.
If the action gets out of order, it simply fails to operate properly and accuracy and spiting of bullet material occur.
Timing, the actual sequence of the cylinder unlocking, rotating, and re-locking is to a very close spec on the Colt, and there is an extremely narrow range of correct adjustment.

The other brands, like S&W, Ruger, Dan Wesson, Taurus, and the later Colt's use the second type system.
The advantages here are, the action requires little hand fitting and this greatly reduces the cost to produce.

Second, even if the action is slightly out of adjustment, the gun still works acceptably.
Third, timing of the action is MUCH less critical.

The down side is, these guns are not as consistently accurate as the older Colt design.

The amount of highly skilled hand fitting is what gives the Colt Python it's reputation for extreme accuracy, and which cause it to be the most expensive production revolver made.
 
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