I know pistols theoretically have multiple safeties, grip, trigger, firing pin (not on series 70 1911’s), etc.
My question is do any of these lock the sear, hammer, or striker? Or are they all related to disconnecting the trigger from the sear or striker? My apology if my question is not applicable to striker design, I don’t know enough to be dangerous regarding how they work.
My Ruger SR9c manual safety locks the striker back. Also there is a striker blocker that prevents it from hitting the primer unless the trigger is pulled back.
Thanks @Zee, the more I know about something the more comfortable I am.
Another area that bothers me is de-cockers. If I understand them correctly they release the hammer by dropping the sear and depend entirely on the firing pin block to prevent a discharge? I personally do not like single point of failure designs.
@Gary_H I understand these things in principle but I’m happy to have someone who knows the details better cover the explanation. I’ve got a Ruger P89 with decocker, and I really like the design, am not aware of any failures with it.
That is a HUGE question! @Zee @Gary_H
I will give due diligence to 1911’s for starters.
Thumb Safety: Physically blocks movement of the sear when the gun is cocked and the safety is ON.
Grip Safety: Physically prevents movement of the trigger when not engaged.
Disconnector: Disconnects the sear and trigger when the slide travels over it and pushes it down. It likewise frees the sear and trigger when released UP into the notch on the slide.
Half Cock Notch: Not really a safety it is an intermediate “catch” for a slow falling hammer as with a sear bounce event from dropping.
Series 80: The half cock notch remains but is irrelevant due to the firing pin lock assembly. An additional lever next to the sear that when the trigger is pulled the lever pushes up on a plunger in the slide allowing free movement of the firing pin. Otherwise the firing pin is heald in place by the plunger preventing a “inertia discharge” of a free floating firing pin.
In General Designs
Pistols:
Slide mounted safety’s: MOST, not all are two piece firing pins with the short part located in the safety barrel (housing if you prefer) when you rotate the safety it also rotates the firing pin out of alignment. Some pistols also de-cock the gun at the same time. Scary as he!! until you figure it out.
Frame mounted safety’s in general BLOCK something from moving, either the trigger or the sear USUALLY.
Revolvers: IN GENERAL most modern ones have some form of “transfer bar safety” a little flat bar that moves up the block the hammer from striking the floating firing pin as the hammer is not going at full speed. Modern (even old modern) revolvers have FLAT hammers that contact a floating firing pin, you can load all 6, 7, 8, 10 cylinders as you wish, some may not have a transfer bar safety.
If you have a revolver (or shot gun) with a “spike” on the hammer NEVER load the chamber it sits on and don’t dry fire them. This is how the old wives tail of not dry firing a shot gun (or any gun) came to be. The hammer with the spike actually entered a hole in the frame to contact the primer (it IS the firing pin) with metal being what it was in 1900 if there was nothing there to “catch” the blow the “spike” could shear off due to inertia = broke gun. Old DBL BBL (stage coach) shot guns were similar in that the firing pin was separate but again with nothing to HIT against it could shear off the point of the pin.
Multiple generations of people were trained NEVER to dry fire their weapons and it lingers on today. As a bit of range etiquette always ASK prior to dry firing someone else’s firearm. It’s prudent and professional.
I will defer to others for striker fired pistols as I have not cracked enough open to be fully versed in their operation. De-cockers have to each be examined on their own merit as I understand there are several ways to do it.
Rifles:
In general if the safety reaches into the guts of the rifle it is blocking the trigger AR-15, Rem 700 et al. If the safety is on the bolt it is a firing pin block. IMHO Paul Mauser had it right.
Cheers,
Craig6
Edited because I kaint speel
@Craig6 you Totally ROCK! 
I was so confused how my Walther PPQ safeties operated until I took it all the way apart and played with all the pieces to figure out how it worked. My concern was I carry appendix and the PPQ has a pre-cocked striker unlike my PPS which has a partially cocked striker. It all made me nervous. Now I’m good though
PPQ, Striker 100% cocked and ready to go. Trigger dingus is depressed allowing the trigger to move back, trigger bar moves back and pushes up on a plunger that moves the striker block out of the way, trigger bar hits the wall and boom. No way the gun can fire unless the trigger is pulled.
@STBR0510 SIR or MA’AM, that is how you begin to learn your firearm!!! Well done!!!
If you don’t know how your junk works, you have no idea HOW IT WORKS. If you are going to place your life in it’s capabilities it is INCUMBENT on YOU to understand it fully.
Cheers,
Craig6
That is a huge answer 
Thank you so much for taking the time for such a comprehensive reply!
I have a series 70 1911 and does the half cock catch stop the hammer short of striking the firing pin because the trigger is not pulled?
@Craig6, I believe a lot of firearm users know how to operate their equipment similar to how they know how to operate their cars with no in depth understanding of how they operate. Thank goodness firearm designs go through extensive validation prior to release to market - and unfortunately they still occassionally have hiccups.
A series 70 was created in 1906 ish. As such machining while perfect for some artisans the vast majority were milled/drilled and ground so there are some vagaries. The half cock IS NOT A SAFETY and much like having an empty chamber it is another step that you have to remember to do prior to getting your gun in action. The half cock is designed ONLY to prevent the hammer from falling on an inertial firing pin (free floating) if bounced off the sear (you dropped it) and the thumb safety and grip safety failed. IMHO it is worthless. but the gov’t liked it. Also IMHO there have been more ND’s trying to get a 1911 to half cock than ever occurred just carrying it cocked and locked.
Cheers,
Craig6
@Gary_H I agree with your assessment that the vast majority of folks that carry do not understand how their firearm works and worse than that have no interest in learning. Bad on them but I hope it works out well for them. MFG’s jump through major hurdles to make their guns “dummy proof” yet dummies sometimes prevail.
Cheers,
Craig6
Well said, good explanation of the various safety mechanisms. I do have to say one thing about the revolver transfer bar. Some of these revolvers usually have a notched hammer so that the transfer bar stays down and away from the firing pin so that the hammer cannot strike the firing pin if dropped or ??? The transfer bar advances up and over the firing pin if and only if the trigger is depressed and held as the hammer travels to the forward (firing) position striking the transfer bar which strikes the firing pin. The “blocking bar” is usually on a flat hammer style revolver and indeed does block the hammer from the firing pin. Anyway, great explanation Craig6.
@Steve36 Thank you for the additional example and expertise! I tried to make this discussion brief yet relevant, hence the term “In General” there are way too many designs out there to hit them all and there are many I am unfamiliar with or have not dissected fully. That and revolvers are not really my thing but I have looked at more than a couple but it has been a while.
Cheers,
Craig6
Yes, particulary with revolvers. Some have sear blocks, some have a block that must be engaged to transfer the strike of the hammer to the firing pin. Ruger Blackhawks are a great example and the first I remember to come with that feature.
Originaly revolvers had the firing pin attached to the hammer, and then suspended in the frame between the hammer and primer but the hammer in both case was always engaged when down so if you dropped it or there was a shock it could fire.
Most all pistols today are “drop save” with either a block or lack of engagement unless the trigger is pulled.
A glock has a two phase trigger, one that allows full travel of the second, but if both are not pressed it cannot fire.
The 1911 has multiple safeties that prevent the hammer from dropping unless they are all engaged but it is still direct engagement when the hammer is down meaning it is in contact with the firing pin and the firing pin then with the primer or close enough to be engaged if dropped/shock.
All your double action striker fired pistols I am aware of will not even cock without the trigger being pulled and the firing pins are free floating. There is a spring that actually keeps it from engaging the primer unless it is fully cocked and then released or some other feature than keeps it from engaging until same.
You’d have to do research on each model you look at to understand the safety features fully. Youtube is a great source of that kind of information.
I just wanted to say Thank You for the excellent coverage on this… that was a lot and I learned some things 
Here’s an article with a nice animation on strike fire in Glocks
Another glock animation
