In response to a question posed on another thread. John...If this should be
in another place, just push the appropriate buttons and send it along.
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The function of a 1911...or any autopistol...depends on everything happening at the right time. Timing is controlled and determined by the inertial mass/weight of a given part or sub-assembly, and the spring that drives it. Every solid object weighs something. That weight determines how much resistance that object resists movement or a change in direction.

The spring that resists and propels an object also has weight, but its
function is determined by its rate of resistance. Recoil springs are rated
in compression, but an often overlooked factor is the rate that it unloads its
stored energy and returns to its relaxed state...or as far as it can go before being forced to stop. The stronger the spring, the faster it unloads this stored energy, and vice-versa. Timing!

Fast-forward to hammer/sear interface, and morph yourself down to
about a millimeter tall, so you can watch the event in slow motion.

Browning's original design for this interface provided slightly undersquare
hammer hooks of about 1/32nd inch long, and a matching...or agreeing
angle on the sear. This provided a captive engagement that tended to force the two parts together more positively. Browning did this because he understood inertia and how easily that those surfaces could disengage
under its effect. This captive engagement provided a margin for error that
made the gun less likely to burst-fire, but didn't do much for the trigger pull
because as the trigger is pulled, it actually pushes the hammer farther back against mainspring tension. Triggers in ordnance-spec pistols
generally ran from 6 to 8 pounds, depending on other factors. Safe,
but not conducive to precision shooting....which wasn't the intent anyway.

When the slide recoils and cocks the hammer, the event is fairly violent.
The hammer overcocks, bounces off the grip safety tang, and the mainspring forces it back down. The face of the hammer hits the slide, and bounces again before it settles down. The slide returns to battery, and the hammer falls further, and is stopped by the sear primary angle catching the hooks.

The slide goes fully to battery, and depending on how smoothly it chambers the round, jerks the pistol forward and slightly down. The hammer, being on a pivot via the pin, obeys Newton's law, tries to stand still, and breaks the contact with the hooks to some degree. If the mainspring is weak, it breaks contact more easily.

Enter the trigger. The trigger has mass and weight. When the slide
slams to battery, the trigger also obeys Professor Newton, and stands still as the gun moves forward. During the firing cycle, the effect is eliminated
because the trigger is held rearward at the limit of its travel, and is disconnected from the sear...so it doesn't have any EFFECT on the sear.

When the gun is being loaded or reloaded with the finger off the trigger, this all changes. The trigger is connected to the sear via the disconnect, and is free to move. Actually, the gun is moving and the trigger is standing still.
As the gun moves forward, the trigger stirrup nudges the disconnect, and
tries to rotate the sear out of hammer hook engagement. If the hammer's
contact with the sear is already lessened through a light mainspring, the sear can escape, and the hammer will fall.

If the sear spring is up to the task, the sear will go back to engagement position, and grab the half-cock notch, stopping the hammer. If the spring
is weak, or has been "tuned" to lighten the trigger pull...it might not stop the hammer, and a slam-fire can result...but usually all that happens is that
the hammer follows the slide, and comes to rest on the slide without
firing...A complete followdown.

The sear can also partially engage the half-cock...or grab it right on the
edge, which can damage the sear's primary angle. There is also the chance
that the sear will engage the hammer hooks right at the edge. This is known
as a false engagement, and will allow the gun to fire with a light nudge on the trigger. Here, the pistol is right on the verge of a burst-fire event.

Enter the "Trigger Job". Military armorers soon discovered that the
engagement angles between the sear and hammer hooks could be changed to make for a better trigger. The hooks were cut square, and the primary angle on the sear altered to agree with that square angle, and thus began the match-grade trigger. Cutting those long hooks shorter and shorter produce better and better triggers, but they found that, beyond a certain point, they became too short for safe and reliable function, and they started playing with sear springs and varying mainspring loads and rates and cut a secondary, or breakaway angle on the side opposite the primary angle.

OOPS! The trigger's mass was the fly in the ointment. It would still nudge the sear out of engagement...so they had to keep the trigger pulled to prevent damage to the narrowed primary angle and crown They lightened the trigger. They lightened the sear. They lightened the hammer. They had to change things in order to compensate for the improved trigger in order to make it function correctly.

Fast-Forward to the 80s...People began to demand better triggers on their 1911s, and were willing to pay for it. Manufacturers responded by giving the public what it wanted, and began to square up the hammer hooks, although they left them long enough to provide a margin of safety, and triggers were better...but still not quite match grade. They were lighter, but didn't break like the proverbial glass rod...and that's what people wanted, for some obscure reason.

About this time, the aftermarket parts suppliers jumped in up to their necks, and provided lighter mainsprings...altered sear springs...hammers with pre-cut hooks that were a little too short for comfort. They also included a
disclaimer. "These parts should be installed by a qualified gunsmith." All these modified parts provided for some very nice, crisp triggers, but they also created a lot of dangerous guns when the disclaimer was ignored and the parts dropped in by the gun owner who didn't understand the "Engineer's First law"...to wit: "Whenever one thing is changed, three other things must be changed to compensate for the improvement."

Bottom line...The trigger group...or fire control group in the pistol is a system that was carefully worked out and proven. There is a window of operation that allows for wear and light damage. The farther from original design parameters that we stray, the narrower that window gets. No such thing as a free lunch, I'm afraid.

The critical parts in the fire control group are:

Mainspring, hammer strut, hammer, trigger, sear, sear spring, disconnect, firing pin and spring. Each one of these parts has an effect on the others to
some degree.

Randomly changing any one part of that system without bringing the others into harmony with the change is risky. You may get away with it and you may not. You may THINK that you've gotten away with it until a little wear occurs, or a spring loses some of its original tension...and things can get informal rather abruptly. Ignoring the gunsmith's dictum that "There's no
such thing as a Drop-In part" can bring you to grief.

John Browning had very good reasons for his specified spring rates and dimensions. I'd be willing to bet that if he were to fire a 1911 with one of the current 3-pound triggers, he'd probably be shocked and would advise the owner to get it fixed before somebody got hurt.

Stand by for Part 2.

Tuner

Excellent job, 1911Tuner. I had the opportunity to watch some high speed film made by S&W of their .45 functioning. The movement of the various parts was frightening. The most disturbing movement was that of the slide stop; I can't understand how it bounced as it did without locking the slide back. The firing sequence was very informative as to muzzle movement. When the pistol fired, the muzzle rose, but it rose even higher when the slide impacted the frame in full recoil. Interestingly, the greatest muzzle displacement was downward when the slide returned to battery. This led me to experiment with reduced power recoil springs to reduce muzzle flip, and I have found that they can work without increasing wear on the pistol. As a competitive shooter, I have found it necessary to maintain my pistols, and do my own trigger jobs. I have found that a McCormick hammer and sear will give me a 3.5 lb trigger with very little work. I usually only have to polish the engagement surfaces (hammer and sear) to achieve this with stock main and sear springs. This combination works great for a match gun, but wouldn't serve for personal defense.

Tuner,

As usually, I just added that in the "Technical Issues" folders of the Home Page and the Forums Site.

Rgds and tnx

__________________
John Caradimas SV1CEC
The M1911 Pistols Organization
http://www.m1911.org

Gammon said:

Excellent job, 1911Tuner. I had the opportunity to watch some high speed film made by S&W of their .45 functioning. The movement of the various parts was frightening. The most disturbing movement was that of the slide stop; I can't understand how it bounced as it did without locking the slide back.

Yep...And that explains why the heavier, extended slide stops often cause
premature slidelock. Inertia!
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The firing sequence was very informative as to muzzle movement. When the pistol fired, the muzzle rose, but it rose even higher when the slide impacted the frame in full recoil.

Bingo! The initial muzzle rise, followed by the sharp slide to frame impact
can cause problems with magazine function...Inertia again. Whether you
realize it or not, you've given a good intro to the next subject in the series. Since you've seen that film, it'll make more sense than it will for many who haven't watched a slow-motion or stop action video of the firing sequence.

I'll post it here, and let John decide where it should go. I'll try to get to it today.


EDIT: I stuck it over in the Gunsmithing section...which is probably the best place for it. ZEN!

Later on!

Tuner

Hi Gammon

Is the S&W film (that you talked about) available on the web or anywhere?

Sounds interesting and, as there's absolutely no chance of me morphing down to micro size (although 75 kgs is within reach), I wouyldn't mind seeing it.

And isn't 1911tuner worth more money?

Cheers from Oz

Davo

What, you mean I should give him another raise????

Stop giving him ideas, next thing he will ask me for vacation time, company car etc.

LoL

__________________
John Caradimas SV1CEC
The M1911 Pistols Organization
http://www.m1911.org

Hi John

Ha, ha, ha! I've got a lot of Greek mates (who are all really stoked up about you guys winning the soccer) and I also worked in the commercial property field for 25 years. I know from experience what hard negotiators the Greeks are!! 1911tuner will have to be a world class negotiator to beat you on a deal!

All the best for the Athens Olympics - we all hope they go really well (with no terrorism). After all, they have to beat the Sydney benchmark!

Ooroo

David

The film I referred to was shown to me by a S&W engineer, and I doubt that it has ever been released for public viewing. The engineer left S&W a long time ago for happier hunting grounds (S&W was tough to work for when the Brits owned it), so I can't even get another look at the film. Too bad, it was fascinating.

Thanks Dave, we all wish the same. Personally I am sure about it.

Rgds

__________________
John Caradimas SV1CEC
The M1911 Pistols Organization
http://www.m1911.org

Actually, I was gonna ask about stock options so I could wear my new suit
to the stockholders' annual thing...