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Old January 19, 2011, 04:52 PM   #1
JN01
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Revolver timing issue

I have a Pietta '51 Navy. The bolt is hitting the edge of the slots on the cylinder by the semi-circular leads. Bolt is of the proper width (fits in the slots). Cocking it slowly, it seems like the bolt doesn't pop up until it is at full cock, but I'm still getting dings at the slot edges. What needs to be done to correct this?
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Old January 19, 2011, 06:56 PM   #2
denster
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Two fixes take your pick. One you can take a few thousandths off the top of the bolt leg that rides on the cam causing the bolt to drop a little earlier and into the lead not past it. Two you can dish the top of the bolt a few thousandths so that onnly the edge of the bolt, which is over the lead touches.
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Old January 19, 2011, 09:48 PM   #3
Doc Hoy
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I am happy (and honored)

to be in Denster's camp when it comes to the bolt leg.

I am a filer not a bender. Every time I even think about bending a bolt leg I get this horrific flash of the leg breaking off. I know that Pietta bolts are cheap but it is the principle of the thing.
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Old January 19, 2011, 10:25 PM   #4
JN01
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Quote:
One you can take a few thousandths off the top of the bolt leg that rides on the cam causing the bolt to drop a little earlier and into the lead not past it.
Right now the bolt is hitting the lead right at the edge of the bolt slot. If it pops up sooner, will it not hit the lead further back and chew it up more? Is that where it is supposed to hit? I was always under the impression that if properly timed, the bolt should pop up exactly in the slot and not touch the lead at all.
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Old January 19, 2011, 11:01 PM   #5
Bill Akins
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There are several issues involved here.

The first thing to know is the reason why colt put the lead in grooves on the cylinder in the first place. That reason is just as valid today as it was back then. In an absolute perfect timing situation the bolt would rise and engage the locking recesses on the cylinder without ever touching the outside and ringing the cylinder. You can time it so it will do that. But....that is only if you cock it exactly the same way and at the same speed each and every time.

When you cock the revolver slowly, the cylinder does not rotate as fast nor have as much rotational inertia as it does when you cock it rapidly. So if you adjusted your timing for perfect bolt drop to slot engagement you would never have a problem. But....if you had it adjusted that way, and then you cocked it rapidly, the cylinder would rotate faster and have more rotational inertia which would cause your cylinder to rotate too rapidly for the slow timing you have set it at, which would cause your cylinder too travel too fast for your bolt and then the cylinder would overtravel before your bolt dropped. (The term bolt "drop" means the bolt rises up to engage the cylinder slots). It can get confusing to folks not familiar with the meaning.

As you can see, this created a situation where if the timing was set absolutely perfect for slow cocking, it would not be set perfect for fast cocking and the cylinder would overtravel. So....colt created the lead in grooves on the cylinder just before each cylinder slot. This is so your timing will work either with slow cocking or fast cocking. The bolt should rise up at the beginning of the lead in groove and then "pop" into place as the cylinder slot rotates to engage the bolt. The lead in groove makes sure your bolt is dropped and ready to go into the cylinder slot no matter whether you have cocked it fast or slow.

Although you can't see it if cocking fast, when you cock it fast, the bolt will actually rise up later in the lead in groove than it will when you cock it slowly. That is because the speed of your cylinder rotation is faster on fast cocking and tries to overtravel your bolt. But the cylinder won't overtravel your bolt as long as you have your bolt timed to drop as the edge of the lead in groove comes into alignment with the edge of the bolt. Your bolt SHOULD drop and engage the lead in groove so it will be ready to "pop" into the slot. That is the purpose of the lead in groove and is proper and normal timing for whatever cocking speed. Yes eventually that will show a mark on your lead in grooves from the blot riding in them. That is also normal. But you can minimize that mark by loosening the tension on your bolt/trigger spring as I describe below.

Luckily on the colt you DO have the lead in grooves. On my 1858 Remington, I don't have the lead in grooves and have to set my timing so that my bolt just barely rises at the edge of my cylinder slot and then as the cylinder continues to rotate the bolt will "pop" into place. That causes a little teeny score mark about 1/32's to 1/16th's of an inch before my cylinder slot. But this is normal. If I had my Remington set to where the bolt rose exactly perfectly as the slot came into engagement with it, the cylinder could overtravel the bolt rise on fast cocking. To minimize the teeny score mark, I lessen the tension on the bolt/trigger spring on my 1858 Remington as I describe to you below later on.

Most used revolvers will have some score marks on their cylinder lead in grooves or a slight ringing around the cylinder. This is just the nature of the mechanics. It can be minimized by proper timing and proper bolt spring tension, or even by filing the head of the bolt at an angle so it will lessen this "ringing" line. But will be seen to some extent on any used black powder revolver. Just one of those things we learn to live with and adjust for. And replace when it gets worn out as does anything.

If your revolver is timed to where your bolt rises at the beginning of the lead in groove, it is properly timed. If you are getting "dings" or "peening" of the edge of the cylinder slot, then back off a bit on your bolt/trigger spring (not the main hammer spring). Backing off a bit on the spring will lessen the tension on the bolt and it will not drop as hard and lessen the "peening" on your cylinder slot edges.

The bolt is a hardened piece of spring steel since its legs have to be tempered to be a spring which presses against and rides up on the hammer cam to teeter totter the bolt as the hammer is cocked. So the bolt is harder than your cylinder and will "ding/peen" the edge of your cylinder slot if the tension on your bolt is too strong. Again, try loosening up on your bolt/trigger spring. Take the cylinder out of the revolver and take off the trigger guard so you can access the bolt/trigger spring. In a trial and error basis, loosen the tension on the spring and cock the revolver to watch the bolt rise up. Push down a little and then release with your finger on the bolt when it is fully risen up. If the bolt goes back down after your pushed on it and did not come fully back up after you released it, your spring tension is too little. Loosen and tighten the spring until you can tell that the bolt fully rises at full cock but is not under undue tension. You do not need as much tension as the spring will put out. It is not necessary and can cause the "peening/dinging" problem you are currently having. All you need is enough bolt tension so that it will rise up and engage the cylinder slots. Just make sure you don't have too little tension either or the bolt can slip out of the slot on fast cock and then you will have cylinder overtravel.

If your bolt is rising too soon and scoring your cylinder BEFORE the bolt is aligned with the lead in slots, that could be caused by a worn cylinder ratchet hand/pawl. That would cause your cylinder to not start turning until the worn hand/pawl engaged the ratchet. If the tip of your hand/pawl is worn, your cylinder will start turning late. That means the bolt will drop off your hammer cam before the cylinder is ready for the bolt to rise into the lead in grooves. To fix this there are two ways. 1. Get a new hand/pawl. 2. Take your old hand/pawl out and set it on a flat metal surface and taking a hammer and punch, carefully "peen" the hand/pawl to elongate it. Now the either new, or "peened" longer hand/pawl will start revolving the cylinder when it should instead of doing it late.

If a bolt is dropping too late and "dinging/peening" the aftermost rear edge of the cylinder slots, you might need to file the leg on the bolt where it engages the cam on the hammer so that the bolt leg drops off the hammer cam earlier. As the hammer is cocked, the cam on the hammer engages the spring tempered leg on the bolt causing the rear leg of the bolt to rise which causes the teeter totter effect which unlocks the bolt from the cylinder. If that hammer cam is worn, it will cause your bolt leg to drop off the cam too early. If your hammer cam is fine but the bolt leg is worn it can cause the bolt leg to drop off the cam too early. And if your bolt leg drops off the cam too late, then you need to file the bolt leg so it drops earlier.

Here is what I do. I inspect the hammer cam. If it is okay then the problem is the bolt. Next I inspect the bolt, if the leg appears okay, it is possible that the leg has just lost a little spring tension where it pushes up against the hammer cam. If I am thinking I am going to have to replace the bolt because the leg is worn out anyway, before I do that, I will VERY CAREFULLY (because it is a tempered spring and will break very very easily) try to spread the bolt legs apart just a little so I re-new and increase the tension of the bolt leg against the hammer cam. If that works then great, otherwise it is time for a new bolt. It's a good idea to have a few extra bolts, bolt/trigger springs, and hand/pawls in your spare parts kit when you go shooting. Also get yourself a good set of NON tapered, counter bored, screwdrivers so you don't mess up the screw threads. And get a little kit of fine needle files too. Also known as Jeweler files. Get a fine filing stone too.
The stone will take off less metal then the files and is good for careful tweaking of parts for timing. A little 220, 400 and 600 grit sandpaper and some small wooden blocks to wrap it around is good too. Even some of the ladies emory boards for filing their nails work for fine tuning timing too. The idea is to always take off less than more and then try it. You can always take off more metal but it is hard to add to once removed.

I hope this helped you understand correct revolver timing and how to fix some problems with that timing.

If you have any other problems I didn't cover, let me know and I will try to help you figure those out.

Last edited by Bill Akins; January 20, 2011 at 08:46 PM.
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Old January 20, 2011, 12:22 AM   #6
denster
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JNO1) Yes that will cause the bolt to drop further back into the lead. I may have misunderstood your original post. I thought your were saying that the bolt was dropping over the inboard edge of the cylinder notch. This would peen that edge which is not a good thing. If your bolt is dropping so that the leading edge is even with the inboard endge of the cylinder notch your timing is right on.
Bill made good reference to the purpose of the leads on Colt style revolvers. Having the bolt drop right into the notch is always a bad thing. Even if you always cock it slow and deliberate with the least amount of wear the heel of the bolt will start to peen the inboard edge of the cylinder notch. Having marks in the leads is the nature of the beast and the only way to avoid it is to never cock the revolver.
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Old January 20, 2011, 03:34 PM   #7
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Makes more sense now. Thanks for the comprehensive description, Bill.

It seems the timing is fine, I'll try backing off the bolt/trigger spring screw a bit. Is the spring tension on that screw enough to keep it in place (if it is not tightened down) or is a bit of blue locktite needed?

I'm thinking that another factor may have been that the face of the bolt itself (that touches the cylinder) was extremely rough. Maybe it was kind of filing the leads. Being careful not to change the shape, I smoothed it out with super fine sand paper and a soft Arkansas stone, then polished it. Maybe it's my imagination, but it seems to cock smoother.
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Old January 20, 2011, 04:04 PM   #8
bighead46
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I thought it was okay for the bolt to pop up in the leade area and then when it actually goes into the slot you should not have to pull the spur on the hammer back more than another 1/4" for the gun to full cock. If you have to draw the hammer back farther you are stressing the mechanism.
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Old January 20, 2011, 04:25 PM   #9
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Great lesson on SA revolver care, Bill. All who own and tinker with SAs should print and save that lesson.
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Old January 20, 2011, 04:27 PM   #10
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Good write-up, Bill. Thankyou.

Quote:
when it actually goes into the slot you should not have to pull the spur on the hammer back more than another 1/4" for the gun to full cock.
If you can pull the hammer back that far after the bolt locks the cylinder, you have a LOT of slop in the whole mechanism.

Ideally, yes, the bolt should drop in the lead at about one full bolt width, maybe a bit more. Then the bolt should drop into the locking slot at the same moment the sear engages. O.K., if you have to have the timing off one way or the other, it is better to have the bolt lock the cylinder just an instant before the sear engages, but not the other way around. You don't want to have the sear engage before the cylinder is locked. This is why the hand length is determined by the sear positions, not by the action of the bolt. Then, the bolt is timed to the rest of the action.

Also, the trigger/bolt spring screw is supposed to be tight. If you want a weaker spring action, either bend the ear of the spring or buy a lighter spring. A loose screw can vibrate loose during firing and leave the bolt loose enough to allow the cylinder to move out of battery.

JMO, FWIW. YMMV, and all that jazz.
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Old January 20, 2011, 09:39 PM   #11
Bill Akins
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Quote:
JNO1 wrote:
Makes more sense now. Thanks for the comprehensive description, Bill.

It seems the timing is fine, I'll try backing off the bolt/trigger spring screw a bit. Is the spring tension on that screw enough to keep it in place (if it is not tightened down) or is a bit of blue locktite needed?

I'm thinking that another factor may have been that the face of the bolt itself (that touches the cylinder) was extremely rough. Maybe it was kind of filing the leads. Being careful not to change the shape, I smoothed it out with super fine sand paper and a soft Arkansas stone, then polished it. Maybe it's my imagination, but it seems to cock smoother.
You're welcome JNO1. Regarding the tension on the bolt/trigger spring, since it is a spring, if you loosen the screw to lighten the tension, the spring itself acts to help keep the screw in place since the spring pushes against the screw and vice versa. But, doing a lot of shooting could possibly vibrate loosen the screw further. I personally have not had my screw become vibrated more loose from shooting and that concern really doesn't bother me because I completely disassemble my black powder revolver anyway for cleaning after I shoot it and then re-adjust my spring screw tension again each time after cleaning. But that could be different on another revolver, even of the same model.

So you can try loosening the spring screw without locktite at first and see how that works out after shooting it. But each individual revolver has its own little quirks. And if you find that your spring screw further vibrates loose after firing, then just put a little blue (not red) locktite on the screw threads. That should stop the screw from vibrating loose from shooting....if you find you have that vibrating loose problem to begin with. I prefer using this method vs trying to bend the spring to lessen its tension which could easily break the spring. (They break easily and frequently enough just from using them normally).

The face of your bolt being rough as you described no doubt was contributing to the scoring of your cylinder. You did exactly right in your correction of it. Did you notice that the head of the bolt is actually angled a bit so that the angle of the bolt head helps to minimize scoring of the cylinder? The reason for that is because as the bolt rises "drops", it is entering into an ever increasingly deeper lead in groove. The hope is (and was by colt) that by putting an angle on the head of the bolt, that the bolt could rise up along with the angle depth cut of the lead in grooves too. The idea was to minimize scoring. Buffing the bolt head like you did will usually help. If it doesn't, you can also very very carefully stone a little more of an angle to the head. But not so much that the low side of the bolt will not adequately hold the side of the cylinder slot.

Take your bolt out and look at it carefully. Then while out, place it into each of your cylinder slots to see how it fits in each one. It should fit all the way down and snug in each slot. Pay particular attention to the low side of the bolt where it is cut lower at the angle I described. Make sure the low side of the bolt is not too drastically angled and that the low side will also adequately lock the cylinder slots. Often folks will file too much on that angle on the bolt head hoping to stop cylinder ringing. If done too much, it will cause the low side of the bolt head to not lock adequately into the cylinder slots on that low angled side of the bolt. There is a lot you can do to minimize scoring and smooth the action up as your found out by stoning and polishing your bolt head. But the whole timing thing is all a trade off of cylinder lead in groove scoring/cylinder "ringing" vs adequate lockup. It is hard to get it exactly perfect and it is a time consuming trail and error thing where you file and stone a bit, put it back together and try that, then stone a bit more and repeat, etc. But with experience you will find that you get it pretty good. And pretty good is usually good enough. You can minimize the scoring and "ringing" of the cylinder, but you can't eliminate it completely.

If your bolt/trigger spring tension is too much, you can get "dinging/peening" on the edge of any particular slot impeding the bolt going in, then you need to very very carefully straight file that cylinder slot edge with your jeweler files. But be careful to keep the cylinder's interior slot sides straight. Don't try to use a dremel for that. Do it by hand and very very carefully. Sometimes you can take a tiny chisel and chip off the teeny sliver of peened metal so the cylinder slot sides are open and true again. That saves you from having to file. This is something you will have to actually do to learn adequately. It's an art that can be taught but must be done to be completely understood. You will learn your own tricks as you go along. Just remember to work slowly and very carefully, those slot edges are a tiny place to work on. A very bright light and a set of magnifying glasses help.

If your cylinder slots eventually becomes too big from wear, you can replace the cylinder, or you can get a new bolt that is oversize and see if that fits your slots better and or file it to fit if the oversize bolt is a tad too large. Another way to get a little more life out of your old cylinder (if it is really worn and an oversize bolt didn't help and you are considering getting a new cylinder anyway)....is by hammer punch "peening" around the edges of the cylinder slots so that you force the metal closer together which will make your slots more narrow again so your bolt locks up tight in them again.

Last edited by Bill Akins; January 20, 2011 at 10:06 PM.
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Old January 20, 2011, 09:53 PM   #12
Bill Akins
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I just wonder if anyone has ever tried this idea.

Modify a bolt head so that it has a teeny free rolling, ball bearing, peen captured in the top of the bolt head so that it not only won't fall out, but can only rise to the normal height of a normal bolt head. The bolt head is made so that the very tip edge of the top of the ball bearing is the top of the bolt head. The ball bearing could be spring loaded or not. It would be easier to make the hole for the bearing if it was lightly spring loaded though. And the sides of the bolt are still the same so it doesn't affect engagement with the side of the cylinder slots.

Now instead of the bolt head dragging across the lead in grooves or ringing your cylinder, the ball bearing just rolls into the lead in grooves and or rolls across the cylinder minimizing scoring and ringing. (The difference between dragging a stone block to the pyramid or rolling it on bearings.) The sides of the bolt would remain unchanged so that lockup remained the same.

I wonder why no one makes bolts like that?

.

Last edited by Bill Akins; January 20, 2011 at 10:10 PM.
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Old January 21, 2011, 10:31 AM   #13
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Quote:
I wonder why no one makes bolts like that?
Probably because to make it free enough to roll, it would be free enough to pop out under the force of recoil, allowing the bolt to drag on the cylinder. Or, if it was tight enough to not pop out, it would soon enough gum up with residue and start dragging on the cylinder.

Even if it was a roller bearing held with a pin, it would still get gummed up. The innards of a revolver are pretty well sealed up, yet fouling still ends up in there. I think that it wouldn't take long before a bolt-tip bearing seized up.

I would be surprised if nobody had thought of such a thing before.
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Old January 21, 2011, 12:30 PM   #14
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I had thought of...

...A narrower bolt which might be a little more forgiving as regards timing but one which is spring loaded sideways in addition to being spring loaded from the bottom. It would be the side force of the spring that holds the pistol in battery.
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Old January 21, 2011, 01:09 PM   #15
denster
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Bill postures an interesting idea. I've never seen it done that way. One way I have seen the issue addressed is the center of the bolt is slightly dished not effecting the height of the leading or trailing edges of the bolt which are what lock the cylinder. What this does is to only allow the trailing edge of the bolt to contact the lead so less metal is dragging across it. It also keeps a bolt that drops a little late from peening the inboard edge of the cylinder notch. This dishing only needs be a few thousandths deep.
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Old January 21, 2011, 03:28 PM   #16
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Quote:
It is hard to get it exactly perfect and it is a time consuming trail and error thing where you file and stone a bit, put it back together and try that, then stone a bit more and repeat, etc. But with experience you will find that you get it pretty good. And pretty good is usually good enough. You can minimize the scoring and "ringing" of the cylinder, but you can't eliminate it completely.
Yeah, a little scoring doesn't bother me, like the ring around a S&W DA cylinder. The leads on my Navy cylinder looked more like a round rasp was dragged across them. I think I have it straightened out now, your comments were particularly helpful. Thanks again.
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Old January 21, 2011, 03:29 PM   #17
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I really got a lot out of reading the posts...

...having to do with the mechanical considerations of timing.

But I would like to take issue with one point. (I hope I am commenting on the right thread)

I never let a wire wheel within ten feet of the parts I am working on. They take metal off too quickly and seem to always leave what appears like a shot-peened finish on the surfaces. It is harder to get that damage out than to use sandpaper, a file, a fastwheel, a stone, or steel wool.

I use a wire wheel for taking paint off of cast iron. That is about it.
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Old January 21, 2011, 06:52 PM   #18
JN01
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Quote:
But I would like to take issue with one point. (I hope I am commenting on the right thread)

I never let a wire wheel within ten feet of the parts I am working on. They take metal off too quickly and seem to always leave what appears like a shot-peened finish on the surfaces. It is harder to get that damage out than to use sandpaper, a file, a fastwheel, a stone, or steel wool.
I think you're referring to this thread:http://thefiringline.com/forums/showthread.php?t=437603
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