Factory Timing Spec Question

[3/4Flap]

A discussion with another Smith aficionado friend of mine & a gunsmith with Smith experience elicited a question. I'm posting it here but it really applies to all years of manufacture. Some years ago I'd just get on phone and call Smith and ask Vito but those days are long gone!

Specifically, does anyone know how timing is checked at the factory on new guns?

Is drag applied? We have come across numbers of new guns of all years which barely lock up on some cylinders without drag and w/ a bit of drag applied don't.

Anybody know how the factory checks accepts/rejects timing on new guns?

 

[Alk8944]

What you are asking about is "Carry-up"!

Timing is the specific alignment of the cylinder charge holes with the barrel bore. These are two separate issues.

 

[3/4Flap]

What you are asking about is "Carry-up"!

Timing is the specific alignment of the cylinder charge holes with the barrel bore. These are two separate issues.

Help me out here. The cylinder is not in alignment if the locking bolt is not engaged in the stop notch (assuming the obvious, that the gun locks up straight).

So how are the two not equated?

Regardless, back to the original question: If it's carry up, how is that tested, accepted or rejected?

 

[RMFnLA]

Interesting question.

Don’t know what the factory does but I introduce a bit of drag when testing cylinder timing; a light finger on the cylinder is all it takes.

You may not realize it, but Smiths do not lock up on the length of the hand but on the width, so trigger travel does not make a difference.

Colt fans would say that’s where they beat S&W.

 

[shawn mccarver]

Start at 4:20 and watch Rico checking carry up and timing, among other things. He goes very fast, so you better pay close attention or you will miss it!
[ame]https://m.youtube.com/watch?v=PQ3HDLkB5l8[/ame]

 

[Alk8944]

Help me out here. The cylinder is not in alignment if the locking bolt is not engaged in the stop notch (assuming the obvious, that the gun locks up straight).

So how are the two not equated?

Regardless, back to the original question: If it's carry up, how is that tested, accepted or rejected?

A revolver can be out-of-time even if it carries up correctly since it is dependent on precise relative alignment of the charge holes and the cylinder stop notches!

I doubt there is a specific requirement for carry-up, it is likely dependent on the habits of the individual fitter. If the carry-up brings the cylinder stop into the stop notch under normal operation it is deemed to be adequate!

I have seen too many posts where the complaint was the cylinder didn't allow the stop to drop into the stop notch on cocking, even on guns NIB! Obviously in those cases there was no confirmation of carry-up either by the fitter or at final inspection.

There is no problem if you apply slight pressure to retard the cylinder when checking carry-up, that is what I do, but if the stop drops into the stop notch on normal cocking it is adequate as the slight mis-alignment that may exist in the timing as a result of clearance between the stop and stop notch width is accommodated by the forcing cone, that is what it is for! Carry-up should be checked with all charge holes loaded.

 

[3/4Flap]

Start at 4:20 and watch Rico checking carry up and timing, among other things. He goes very fast, so you better pay close attention or you will miss it!
Smith & Wesson Pro Series | Shooting USA - YouTube

Wow.

I wonder how long that system has been used...

Very interesting and thanks very much for posting.

 

[3/4Flap]

A revolver can be out-of-time even if it carries up correctly since it is dependent on precise relative alignment of the charge holes and the cylinder stop notches!

I doubt there is a specific requirement for carry-up, it is likely dependent on the habits of the individual fitter. If the carry-up brings the cylinder stop into the stop notch under normal operation it is deemed to be adequate!

I have seen too many posts where the complaint was the cylinder didn't allow the stop to drop into the stop notch on cocking, even on guns NIB! Obviously in those cases there was no confirmation of carry-up either by the fitter or at final inspection.

There is no problem if you apply slight pressure to retard the cylinder when checking carry-up, that is what I do, but if the stop drops into the stop notch on normal cocking it is adequate as the slight mis-alignment that may exist in the timing as a result of clearance between the stop and stop notch width is accommodated by the forcing cone, that is what it is for! Carry-up should be checked with all charge holes loaded.

Thanks very much. Very clear explanation.

 

[RMFnLA]

Start at 4:20 and watch Rico checking carry up and timing, among other things. He goes very fast, so you better pay close attention or you will miss it!
Smith & Wesson Pro Series | Shooting USA - YouTube

What a cool video; thanks for sharing it!

 

[Biggfoot44]

Yikes! I'm going to have to tweak my vocabulary.

My inspection protocol is good , but verbally I considered Carry Up as one part of Timing , and chamber position relative to forcing cone as " Alignment " .

 

[Greg11H20]

What you are asking about is "Carry-up"!

Timing is the specific alignment of the cylinder charge holes with the barrel bore. These are two separate issues.

Timing and carry-up are one and the same. Carry-up is a term that came on the scene in the past 20 years, much like "trigger press" made a feeble attempt at replacing "trigger squeeze".

Your reference to "charge holes" is incorrect as well. They are "chambers"....now you might be thinking back to the Colt Dragoon you used back in the 1800's, those black powder guns had charge holes.

 

[WR Moore]

Unless the shaft for the forcing cone reamer is a good tight fit to the bore, I think I now know why some forcing cones don't seem to be concentric to the bore.

Seems to be worse on 2" guns, but then there isn't a lot to align/stabilize the reamer.

 

[3/4Flap]

Start at 4:20 and watch Rico checking carry up and timing, among other things. He goes very fast, so you better pay close attention or you will miss it!
Smith & Wesson Pro Series | Shooting USA - YouTube

I'd like to know how that tool works....

Any gunsmiths out there that have one?

 

[Greg11H20]

I was a Savannah Police Officer for a number of years and we were issued new Model 67's. Mine was out of time on every chamber, cocking it moderately slow in single action, the cylinder stop would not click into the cylinder stop notches. The Department Armorer, who had been on the department for over 30 years, drenched the innards with break-free and told me to dry fire it daily for a week or so, he said it needed to "worn in" to time. He said it was common for stainless S&W revolvers to be like that. I thought he was nuts, but being new, I followed his advice. Sure enough, the gun wore in, and turned out to be a great shooter.

 

[steelslaver]

Unless the shaft for the forcing cone reamer is a good tight fit to the bore, I think I now know why some forcing cones don't seem to be concentric to the bore.

Seems to be worse on 2" guns, but then there isn't a lot to align/stabilize the reamer.

The shaft for the forcing cone cutter and the cutter that does the final face cut for the barrel extension for cylinder clearance are only about .025, But I run a land diameter bushing about 1" long on my shaft when I do either. I do not know about the factory. But, the one for forcing cone should self center unless you forced it to one side or the other with the nylon block used to exert pressure on it.
At the speed the guy in video is pulling trigger the cylinders inertia would cause it to lock up even if the hand did not. Notice he also does it with all the chambers empty. If you had a slightly sloppy ratchet to cylinder fit, filling the chambers would cause the ratchet be held turned into the hand instead of allowing it to move away from hand in cylinder and you could get a sticky spot right at end of trigger pull if the ratchet was a bit sloppy and dead on with empty chambers. The new style ratchets with the flat on shaft and the odd end arms are much more precise with less movement empty than the old style with groove and pins

 

[3/4Flap]

The shaft for the forcing cone cutter and the cutter that does the final face cut for the barrel extension for cylinder clearance are only about .025, But I run a land diameter bushing about 1" long on my shaft when I do either. I do not know about the factory. But, the one for forcing cone should self center unless you forced it to one side or the other with the nylon block used to exert pressure on it.
At the speed the guy in video is pulling trigger the cylinders inertia would cause it to lock up even if the hand did not. Notice he also does it with all the chambers empty. If you had a slightly sloppy ratchet to cylinder fit, filling the chambers would cause the ratchet be held turned into the hand instead of allowing it to move away from hand in cylinder and you could get a sticky spot right at end of trigger pull if the ratchet was a bit sloppy and dead on with empty chambers. The new style ratchets with the flat on shaft and the odd end arms are much more precise with less movement empty than the old style with groove and pins

Do you know what the tool referenced above is that was used in the video?

 

[press-1-for-english]

Timing and carry-up are one and the same. Carry-up is a term that came on the scene in the past 20 years, much like "trigger press" made a feeble attempt at replacing "trigger squeeze".

Your reference to "charge holes" is incorrect as well. They are "chambers"....now you might be thinking back to the Colt Dragoon you used back in the 1800's, those black powder guns had charge holes.

I have been calling them "chambers" for the better part of my life but in the video, at 05:29, the narrator uses the phrase "charge holes".