[heviarti]

I've been designing a double action revolver, and need to speak with someone who knows alot about double action internals and design. I've emailed some pretty well known people and as yet have not been able to get any info from anyone.

I'm planning on optimizing the design for speed shooting, and I am curious what factors affect the quickness of a double action revolver. I know that to date the Smith is always the fastest, regardless of frame size, but I want to one up the Smith. I know the factors that must cause this are pin diameter (bearing surface) pin to pin dimension and lobe angles on the working parts. but what specifically makes it do what? for each of these variables, there must be a point at which they are too little or too much. what effect does each have? what factors affect the suitability of the action to so called "trigger cocking"?

I hope I can find someone that knows something. it seems like even the greats out there only know how to fix one, not design one.

[Jim K]

Well technically, double action and trigger cocking are two different things. The old Starr "double action" is really a trigger cocker in that the trigger only cocks the hammer; whether the follow through fires the gun depends on the setting of the slide on the trigger.

I am not sure how you mean to "one up" S&W. If you want to look up the various British and American patents from the 1860's to 1970's, it seems like just about every type of DA system has been tried, including several by S&W (S&W tried to keep the same external shape, but they went through a bunch of different internal systems before sort of settling on the present one).

Things like pin diameters are part of tolerances, a manufacturing question which really involves cost, not a design issue. A DA revolver needs to carry out a set cycle. Free the cylinder to turn, turn the cylinder, lock the cylinder in place, fire the round, keep the cylinder locked so it can't be turned accidentally (e.g., by rubbing on a holster). Of course, a system of extracting fired cases and loading must be incorporated.

Exotic systems like automatic revolvers (Union, Webley-Fosbery, Mateba) usually have not had a lot of success, as they are a solution in search of a problem. Top break revolvers seem to some a good idea, but any joint is a point of weakness that will eventually open up, even with mild loads.

P.S. If you want to know S&W's little secret on DA shooting, look closely at the trigger-hammer interface. Then look at the Colt DA in the same area. If you don't see a whole lot of difference, keep your day job.

Jim

[heviarti]

Trigger cocking as in pulling and holding on a DA before the trigger breaks. some match shooters do it. I intend to one up Smith in that I am designing something specifically for speed shooting. There is likely a big difference between the things that need to be left in the action for a carry pistol that have no effect in the end on speed, or infact slow the action down.

As to pins, Wouldn't I get more bearing surface on a .250 pin than a .125 pin? that would give me more lubricated surface, and a lighter moving part.

As to the smith and the colt, I know the colt tends to have a physically longer action, and tends to be a bit more delicate. I haven't been able to find a set of cutaway or cycle drawings. Our town is located in the figurative butt of the world, and our library is about equivalent to the lint found in same....

I've had some single actions apart, but haven't really had a double to fool with.

[Old Fuff]

P.S. If you want to know S&W's little secret on DA shooting, look closely at the trigger-hammer interface. Then look at the Colt DA in the same area. If you don't see a whole lot of difference, keep your day job.

Ah so.... :D Jim just gave you a big clue.

Colt's first double action revolver dates from 1877, and S&W's first atempt was a top break .32 that first saw the light of day in 1880. Explaining all of the differences could take a book. Perhaps the most difficult problem is keeping the cylinder stop (called a "bolt" in Colt's) from chewing up the notches in the cylinder. The next is to keep the cylinder yoke ("crane" in Colt talk) from getting sprung. It is generally acknowledged that the best double action lockwork was made in S&W revolvers produced from 1910 through 1948 These were called "long actions" because the hammer rotated backwards further in double-action so the hammer hit harder when it went forward. Other makes of revolvers, then and now, did not have this feature.

Smith & Wesson cured the notch-battering issue for a time by cutting a grove next the the cylinder notch, and inserting a hardened steel shim. The works was so precise that you often can't see the shim. No company would try to do that kind of work today.

Back in the top-break days of the 1890's and early 1900's Smith & Wesson mounted their mainspring in such a way as the cause the double-action trigger pull to drop, just before the hammer was released. This sent a signal to the shooter to get his sights aligned because his revolver was about to fire. An interesting feature, but now long forgotten.

[asknight]

As to pins, Wouldn't I get more bearing surface on a .250 pin than a .125 pin? that would give me more lubricated surface, and a lighter moving part.

Sure, you'd have more bearing surface but basic metallurgy coursework will explain that the larger the bearing surface (lubricated or not), the more resistance in moving against it. Think of speedskaters on ice skates... that will explain it somewhat.

I think you'll have to define "lubrication" before you design a part that requires it to function.

[heviarti]

Note taken about the bolt. I'd like to see an actual example of that. Crane will not be an issue, because I'm looking at a top break, but one that fires from 6:00. I know this is going to cause alot of... fun designing the release for the automatic ejector, and in getting the hammer to make enough striking force to ignite the primer seeing as the spur will ride high. (ran into a site talking about those problems in something or other and decided to adopt them so i could work around them.)

I'm going to look very seriously at the ejector on a webley, because they were very rugged, and will practically throw the brass out of the cylinder. I may end up having to use a speed loader to reset the ejector.

as to lubrication, there is a critical dimension at which oil (looking at a light viscosity.. I've had bad luck with greases.) will "float" a metal part. it will also hold a seal at that domension. I think it's like .001 or .003 (I have it written down somewhere in my notes for the design.) I'm looking at electropolishing the bearing surfaces, after having seen the capabilities of electropolishing in a processing environment. I am hoping that two small parts won't tend to bind between the electropolish and the oil, though I think it less likely with a rotating part than two flat surfaces.

all of this still doesn't take into account what I'm really worried about. I can hash out all those details in wooden models. I'm trying to find a starting point for some lobe dimensions, and degrees of travel, and again, pin distances, because the dimension between the centerlines of two pins on which primary moving parts rotate will in the end have an effect on the theoretical maximum speed of operation of the action. as will the lobe dimensions... as will many other component relationship issues. I don't particularly relish doing 140 years worth of experimentation to be left with something at the level I intend to better. I'm looking at splitting hairs here. If I can get the action to where it operates smoothly, easily and reliably at such a speed it is capable of cycling just slower than the bullet can get into the barrel (so I don't shave lead, or even worse, contain the bullet againt the frame and kb the thing) I don't expect to get that much out of it, but that's the unattainable goal to strive for. at that rate, maybe I can get something that a professional like Jerry Miculek could use to gain a millisecond or two on the Smith.

Noone has been able to suggest any books or other reading on design, so I've got to start by picking a few brains... so here I am.

[Old Fuff]

You seem to be focused on the tree (revolver lockwork) and not the forest (the whole revolver).

You want the fastest possible double action. This means that the cylinder must revolve as quickly as the lockwork does. The cylinder is a relatively heavy part, and if it's spinning fast enough its momentum may carry it ahead of the hand that was pressing on the ratchet - in which case it may go past the cylinder stop notch coming up for the next chamber. If it doesn't the ball on the cylinder stop (the part of the stop that sticks up into the cylinder window in the frame) will stop and lock the cylinder so abruptly that the ball batters and peens out the notch, causing the lock-up to become loose, and allows the chamber/bore alignment to become non-concentric.

Ya' need to look at the whole picture...

[Jim K]

The idea of a top break firing from the bottom chamber has been done. Regardless, there is still strain on the joints and they will eventually shoot loose. Are you sure you are not just trying to be different, rather than actually trying to be better?

As to pin size, the designer chooses the size needed for the job. There is no use trying to put a half inch hammer pin in a J-frame size revolver, or a hairpin for a slide stop pin in a 1911. That kind of thing is called engineering, which is why gun companies pay nice salaries to graduate engineers and metallurgists, not to folks who just think they have a better idea.

And don't forget those patents. Even big companies sometimes do. The first Remington Model 700 production was ready for shipment, when they found out that the sear infringed a Winchester patent. Ooops! So they had to redesign the sear and retrofit several thousand guns.

Jim

[heviarti]

one, the cylinder is part of the lockwork as far as I am concerned. I know it's going to have to have very low inertia, and will probably have to be made of an exotic material. Thanks for the pointer on travel off the pawl. I have a few ideas for counteracting that.

The only 6:00 fire revolver I've seen so far is the mateba, and it's not a top break. I'd like to see the example you are speaking of. I'm curious to see how their ejector operates, and compare it with a couple of the ideas i've been considering. The hinge is a weak spot on most break-opens, and I've been considering some ideas to counteract loosening. This thing will mainly live on paper, aside from the wooden models until i can find someone actually lisenced to build a firearm. If there are ever more than five in existance, it'll be too many. This is not intended to be a production piece, or even feasable for mass production. It's primarily intended as an excercise in designing a precision instrument.

as to "engineering" some of the rock stupidest things I've ever seen have been designed by engineers with alot of paper on their wall, but no actual skill in design. I've even got a relative who is an internal combustion engineer who couldn't even set up the throttle and choke on his lawn mower. He transposed them and never could figure out why it didn't run. Hooray for the salaried engineer. Remember the best innovations in firearms design have often come from places other than the industry. I really don't fool with wheel guns, and have never had much of an interest in them until recently.

That said, the J is an awfully small frame, but what would the ultimate effect of a hammer pin twice the size of the standard one be? would it tend to bind? would it raise or lower the speed of the hammer, increase or decrease the effort required to cycle the action? If the larger frame with larger parts, dimensions, and weights cycles as fast as the smaller frame, (according to Jerry Miculek) It's primarily a question of geometry, lift, durations, percentage of spring weight to dimension size, and percentage of increase in dimension to scale. Smith has found something that works well, it's easily adapted to multiple sizes, and configurations and is wonderfully adapted to mass production. That's not what I'm looking at. I've got a few set criteria and I intend to design something that does exactly that. I simply don't have the time and money to invest in buying every double action revolver since the Adams, and pick each one apart.

There's little or no reading material on the subject, and I haven't found any schematics or cycle drawings of anything other than a fundamental rendering of the basic principle if a double action. I'd kill the President of Paraguay with a fork to get my hands on a Webley in .455 for about an hour and just measure every surface on the cylinder and pin. Unfortunately the only break top I've found in this area is an old H&R in .32. I learned some things from it. I'd have learned as much from a good set of machine drawings. It's lock is not applicable to the cartridge i'm thinking of, so next chance I get to look at the Schofield and Webley, I'll take a look at the advantages and disadvantages, and more importantly, see how they age. then I'll design something for the lock.

But first and foremost, I'm looking to discuss the finer points of the inside of a Smith, it's flaws and failings, and it's triumphs. I could easily come up with something that works. I just want to do better than that.