View Full Version : Trigger mechanism on a revolver.

November 5, 2001, 10:12 PM
I tried this in the revolver forum but only got two responses. I have the pic of the revolver off S&Ws site but it is too busy and I don't know what i'm looking for. I need to know exactly how a da/sa revolver trigger works. howstuffworks.com only has a DA trigger.

James K
November 5, 2001, 10:52 PM
I am not clear exactly what you are asking, but here goes on revolver hammers and triggers.

A single action hammer generally has a notch into which a sear (often just the upper part of the trigger) fits. This holds the hammer back until the trigger is pulled. Then the hammer falls, and the firing pin (which may be part of the hammer) indents the primer firing the cartridge. The hammer has to be cocked by hand for each shot. The trigger pull is usually light.

A double action (only) hammer has a device which allows it to be pushed back by a part of the trigger as it is pulled. That device usually takes the form of a strut which is spring loaded. A "shelf" on the rear of the trigger engages the strut and pushes it up when the trigger is pulled; the strut pushes the hammer up and back. When the trigger slips off the end of the strut, the hammer falls. The strut is pushed back out of the way and then resets when the trigger returns to its rest position. The trigger pull is usually long and fairly hard.

A double action trigger may also have a single action capability, allowing the hammer to be cocked manually if a lighter trigger pull is desired. Most modern police and defense revolvers use this type of mechanism. The hammer has a notch into which a sear, again usually part of the trigger, will fit when the hammer is pulled back manually. The sear part of the trigger is usually at the rear of the "shelf" that contacts the strut to raise the hammer in double action use. The hammer notch is at the bottom front of the hammer, below the strut. Both the sear and notch are rather unobtrusive and not easily seen in a picture.


(That Howstuffworks site is confusing. If you can point me to the picture you are looking at, I could address it directly.)


November 6, 2001, 06:54 AM
Well done Jim.


November 6, 2001, 07:52 PM
Thanks, I get it now. You have to search for machine gun on how stuff works, it's a flash animation so I can't display it here. Ok, on the cylinder detentes... the stop comes in on the non lead-in side then moves out the little lead-in as you pull the trigger or the other way around?

James K
November 7, 2001, 08:04 PM
The other way around. The leade is designed to let the cylinder stop begin to move into the notch before the cylinder lines up so that it has more bearing surface to stop the cylinder. Some very early revolvers, like the Colt Paterson and Dragoon did not have leades, but all modern revolvers have them.

On some revolvers, such as Colt type single actions, the cylinder stop should not contact the cylinder until it reaches the leade. On other revolvers, like the S&W, the cylinder stop will normally "drop" halfway between notches, leaving a rub mark; this is perfectly normal and beyond wearing a line in the blue will cause no problem.

FWIW, you can use the leades to determine at a glance which way the cylinder turns. They are like little arrows pointing in the direction of rotation.


November 8, 2001, 02:28 AM
For some background information, I need this info for a project I have. I'm building a pneumatic revolver, I have everything designed except the trigger and hammer mechanism. It's going to be at least 8 months before I can begin milling pieces but I want the design to be done now. I will be making it primarily out of aluminum, probably T6061.

Walt Sherrill
November 8, 2001, 09:24 AM
Manufacturing a gun is dangerous business -- from a legal, if not a safety -- point of view.

Since you're unclear about basic gun functionality, its probably a safe bet you're not a licensed gunsmith, etc.

There are federal laws against manufacturing; it requires a special federal firearms license. You might be safe as long as you don't sell it (or even give it) to someone, but otherwise, watch out. (If found to be "manufacturing" without a license, you could lose all future rights to own guns, get stuck with a big fine, and even end up in jail...)

Maybe you should be designing a nail-driving machine, instead of a pneumatic gun.

James K
November 9, 2001, 01:13 AM
It is legal to manufacture a firearm (other than a semi-automatic assault weapon) for one's own use; only if it is a full automatic, is BATF approval required. "Manufacture" here means making the receiver or frame of a firearm. Merely assembling a firearm from parts on a purchased receiver is not manufacturing a firearm.

Note that about one's own use. If you contract out the manufacture of the receiver or frame, the contractor must have a manufacturer's license, since HE is not making it for HIS own use.

However, if the gun is truly pneumatic, that is if it expels a projectile by air pressure rather than by explosive, it is not a firearm under Federal law and no license is required. Some states, though, place restrictions on "high power" air rifles and pistols (usually a muzzle velocity figure) so it is a good idea to check local laws as well as federal.


November 9, 2001, 08:00 PM
Its a pneumatic revolver, not a firearm. Manufacture isn't limited by any statues i'm familiar with other than minimum safe wall thickness to retain maximum possible pressure. I'm familiar with pneumatic design and trigger mechanisms of many models, just not a revolver mechanism since virtually no pneumatic revolvers have been made.

James K
November 11, 2001, 12:31 AM
Hi, Skyssx,

---"virtually no pneumatic revolvers have been made" ---

Maybe there are reasons for that. We would all appreciate hearing how you get along; it sounds like a neat project.


Mike Irwin
November 11, 2001, 01:14 AM
Crossman had, for years, a series of pellet revolvers that used the CO2 cylinders. They may still make them.