S&W 640 Timing

R

roklok

New member
I am looking for a little experienced input. I have a S&W 640-1 that has a timing issue. On 3 out of the 5 chambers, the hammer falls before cylinder locks up. The two chambers that lock up before hammer falls are next to each other (subsequent).

Is this indicative of a hand problem or an extractor problem ? It seems to me that if it was a hand issue, none of the chambers would be timed right. I am wondering if a new extractor assembly would solve the problem.

Another question, where is a source of oversize J-frame hands ? Oversize hands are available from numerous vendors for bigger frames, but not for the J-frame. I did find an oversize J frame hand at Numrich, but received it today and it is a POS. Looks like it was made by cavemen by shaping it with rocks. I think a better example would come out of Khyber Pass. The pins are crooked, and it is actually smaller than the original hand. I installed it, and none of the chambers locked up.

Thanks in advance for any input.
 
S&W timing

Sir;
With the original factory parts what you experienced was a problem with the "star" or rachet! This is common with S&W and several other revolvers. We would test S&Ws with a box of 44 magnum and several cylinders would be "out of time." Revolvers need a front crane lock-up! S&W doesn't have one, thus they have crane play! When you have crane play you can effect the timing. The real cure is to send it back to S&W and have them fit a new, thicker, hand and star.
This is a continual problem with S&W revolvers but most shooters aren't astute enough to notice it - you are. But when shooting a S&W you generally cock it or d.a. it so fast that you don't notice it - the cylinder continues on around of its own weight - but when you cock it slowly you can see it - I've seen literally hundreds of revolvers with this problem, that's why I like the Ruger Redhawk and super, and also the Taurus Raging Bull series in 480 Ruger!
Harry B.
 
As above, failure to lock up fully before hammer drop is a defect that needs repair.

This is caused by either a worn gun, or occasionally a factory defect.
In either case, I recommend a trip back to S&W for a proper repair by the experts.
Just what the fix is depends on what the problem is.
The problems can range from a cylinder yoke bent, a forward lock failing to lock tightly, a worn or mis-fit hand, or a worn or improperly fit ejector, etc.

In most cases, its nothing the average owner can repair at home, and you MUST know precisely what the problem is before attempting any repair.
Local gunsmiths may be able to repair it, or they may cause further problems by a botched repair.
That's why I recommend S&W. They know more than anyone about it and they have all the parts.

If the gun is a newer one, repair may be free.
 
timing

Sirs;
In my early years the Ruger Blackhawk S.A. revolvers were bad in this regard. The sear would engage the hammer at full cock and you had to pull the hammer back further to get the cylinder bolt to lock. I solved this by removing the hand on the hammer and gently peening it, lengthening it some (measure it with dial calipers) - it did not injure the hand but cured the problem by letting cylinder lock bolt and sear engage at the same time and removed the pull back of the hammer.
However, this is not true with S&W or Colt, and some others! First, you need no more than .001 endshake on the cylinder, a .004 to(no more than) an .006 barrel cylinder gap and to install a very good, tight ball lock in the crane to hold it tight to the frame. Then you would need a thicker hand (from Brownells) and fit the star to it - not the hand to the star! On the star your contact points for the new hand must be perfectly equal. This takes an expert and alot of hand work - YOU CANNOT PEEN THE STARS ON YOUR RATCHET!
Harry B.
 
I really have to disagree to a point. Many revolvers will fail to lock up if (as often recommended) one holds the cylinder tightly, deliberately preventing it from turning. Of course doing this to test the revolver can also break or bend parts, but then we just have to test that lockup, don't we? Maybe putting a pipe wrench on the cylinder and pulling the trigger with a pry bar would really check the lockup.

Come on, guys. S&W says that final alignment is done by the bullet itself. If the gun shows no problem in normal firing, doesn't spit lead, and the firing pin strike is centered in the primer, is the gun really a piece of junk that has to be worked on at the factory or by some guy with a big hammer? I don't think so. Perfection is nice, but sometimes it is not necessary.

Jim
 
Thanks for the replies, I really hate to send it back to S&W, but maybe that would be the best course of action. I am confident that IF it was a hand issue, and oversize hands were available that I could fix it myself. However, being that on two of the chambers it does lock up, I am thinking it has more to do with the "star" on the extractor assembly. I have owned this revolver since new, over 14 years ago, but the crane is tight, I dont think the problem has anything to do with a sprung crane or excessive endshake.

This revolver fails to lock up with NO load on the cylinder. In other words, without touching the cylinder, it fails to lock before hammer drop on 3 of the 5 chambers. I am wanting to get the issue fixed before I possibly crack the forcing cone.
 
S&W

Sirs;
If S&W says that final alignment is done by the bullet itself I never want to touch a S&W again - I've never heard of this!
I don't put tension on the cylinder to check lock-up - you can do it by slowly cocking the revolver.
Harry B.
 
Just wanted to let those interested know that I fixed the timing problem in my 640. Harry Bonar was right, and my suspicions were correct, the problem was the "star" on the extractor assembly. I closely examined the individual "hooks" on the "star" and was able to predict which chambers would lock up by looking at the star. There were three hooks that were visibly shorter than the other two. The side of the hand pushes against these hooks to rotate the cylinder the last bit for lock up.

I bought a new extractor from Brownells and installed it today. It fit the cylinder perfectly, no fitting required. The individual hooks on the star needed filed to lock up correctly. I took my time, filing with a needle file until I could pull the trigger until hammer drop with no resistance. I did not force the trigger, at first the trigger would stop well before hammer drop. After I got a hook fitted, I would mark it with black marker and move onto the next one. It took me about two hours to file all five hooks for correct lockup.

I am including some pictures of the extractor assembly with three of the hooks fitted (the ones with black marker on). My file is pointing to the tip of the hook that needed filed. The empty casings are in the cylinder to fully support the extractor to ensure it is in the proper position for timing.
 

Attachments

  • S7300372.jpg
    S7300372.jpg
    72.3 KB · Views: 81
  • S7300373.jpg
    S7300373.jpg
    58.6 KB · Views: 68
Sorry, Harry, no more S&Ws for you. That is what the factory says. Of course they are not talking about a cylinder being off 1/4 inch, just the normal little wiggle you get with a lot of S&Ws.

Also don't buy a Colt because, while they seem to lock up tight thanks to the two step hand, that hand can also force the cylinder out of alignment if the bolt or cylinder notches are worn.

Jim
 
You must log in or register to reply here.
Back
Top