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Discussion Starter #1
Hi,

I'm new to the forum and have really enjoyed reading and learning all I can about Colt DA revolvers. I have several S&W revolvers, but recently I purchased my first Colt, a late '60 PPS in .38 spl, the gun is 98%. It has been fired some but looks to be very little.

In all of my excitement, I took it to the range for session and to test it out. I have no safe queens, or a least not yet. I was shooting boxed ammo 158 gr RNFP FMJ. The first cylinder I shot in single action without any issues. Accuracy at 7 yds was what I expected. The second cylinder I tried to shoot in double action. On the first round I had a failure to fire. Thought it might be a light strike, so fired the next round without a problem. All six rounds fired from the gun but I notice that one maybe two of the rounds key-holed into the target. Upon further inspection I found two cooper shavings on the firing bench. Two of the spent cartridge’s had off center firing pin strikes. After noticing this, I put the gun in my range bag and didn't attempt to shoot it anymore.

When I got back to the house, I started doing more research to try and figure out what was causing the problem. I found dfariswheel's post (thanks) on Colt revolver timing checks and went through the procedure with my PPS. Should have done this prior, and yes, I have learned my lesson.

The bolt retraction and snap back look to be correct.

The bolt snaps into the ramp just about in the middle 1/3 as the procedure calls for.

When cocking the hammer the bolt drops into the locking notch exactly when the hammer is fully retracted. There seems to be backward lurch on the hammer when the cylinder goes into lockup. I can’t get the gun to fully cock the hammer without the cylinder going into lockup. So it appears that SA mode is fine.

I can get the gun to fire out of lockup when trying to stage the trigger in DA mode, I was able to reproduce this on the bench when I very carefully and very slowly pull the trigger until the hammer releases and stop pulling the trigger immediately. The cylinder is roughly .005” from lockup but that’s enough to cause lead shaving. If I continue to pull the trigger the cylinder does go into full lockup.

It seems to me the hammer is dropping early in DA mode and it is causing a race condition between the hammer falling and pulling the trigger all the way back to complete the full cylinder lockup.

Is this normal? Can it be fixed? Should I not try to stage the hammer in DA?

I appreciate all comments and suggestions.
I apologize for the long post. Please provide a link if this has been previously discussed.
 

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Your Colt could be getting a little worn and may be almost to the point where it needs normal maintenance.
What usually needs maintenance is to have the hand that advances the cylinder either stretched, or replaced if it's been stretched in the past.

"Staging" is something that takes a lot of practice, and you still can "miss" and cause over-rotation, known as "Cylinder throw-by".
This can be worse if the hand is getting worn and you pull the trigger VERY slowly.
Until you have the gun inspected I'd stop staging it.

If you want to have it serviced, Colt still works on them and so does Frank Glenn.
 

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Discussion Starter #3
Thank you for your reply, I respect your opinion. I certainly won't be using DA until I get the gun inspected by a gunsmith. I've read that over-rotation can be caused by DA rapid firing. I thought what I described would be called under-rotation? i.e. During DA trigger staging, the hammer drops prior to the bolt locking the cylinder. Once this happens, pulling the trigger the rest of the way back causes the cylinder to lockup after the hammer has dropped. Maybe I don't understand what over rotation is.
 

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Sorry, I may have mis-read your first post.

If you're "staging" the trigger, (giving it a sudden jerk to get the cylinder to unlock and rotate and lock at the next chamber, it's possible to get throw-by, in which the cylinder rotates TOO far when the locking bolt fails to catch it. This causes the firing pin to strike off center and allows firing in an unlocked condition.

If you very, very slowly pull the trigger in double action it's possible the hammer can drop and the cylinder to not be forced all the way to lock up.
The answer here is..... don't do that, until you get the gun checked out.
In most cases, unless the gun is well out of time, it's almost impossible to pull the trigger in DA and allow the hammer to drop without the cylinder being pushed into lock up.
If you're "milking" the trigger so carefully and slowly that the hammer is dropping and the gun is firing before the cylinder locks, you need to get timing adjusted.
 

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Discussion Starter #5
Thanks, i'll get the timing checked as soon as I can find a local gunsmith that will work on Colts. Anyone know of a good one in the Houston area?

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