1911 fires through thumb safety

[Hoxviii]

Looking for input on what would cause a 1911 on thumb safe to sweep the safety off upon squeezing the trigger, allowing it to fall full forward.

First detail strip on this specific pistol, went back together, safety on, squeezed trigger and click. tried again to make sure, click.

Tore down, made sure it was back together correctly, try again, pulls through safe for fire.

Anyone, anything?

 

[David E]

The thumb safety is improperly fitted. A properly fitted safety prevents the trigger bow from moving backward at all. Yours does not. It allows the trigger to disengage the sear, dropping the hammer.

You need a new thumb safety properly fitted to the gun.

 

[1911Tuner]

The thumb safety is improperly fitted.

Yep.

A properly fitted safety prevents the trigger bow from moving backward

The thumb safety doesn't prevent the trigger from moving...not directly anyway. The grip safety blocks the trigger. The thumb safety blocks the sear.

Incidentally...This post should also remove any question as to whether or not the thumb safety blocks the hammer. It doesn't.

 

[batoy1911]

If the thumb safety is moved down by pulling the trigger, the geometry of the projection on the inside of the thumb safety which blocks the sear is maybe wrong. It could be that it meets the sear at an angle instead of perpendicular to it. The sear could also have an out of spec geometry. Or maybe a combination of both. Another posibility I can think of is that the thumb safety doesn't completely block the sear. In which case the sear just pushes the thumb safety down as it moves in an arc. The sear will fall without much if any resistance from the safety. Mislocated holes? I'm guessing of course.

Still guessing... if the hammer falls but the thumb safety is not moved, the part of the safety that blocks the sear could have been overcut.

 

[1911Tuner]

If the thumb safety is moved down by pulling the trigger,

The thumb safety isn't being moved by pulling the trigger. The sear moves because the thumb safety isn't blocking it, and releases the hammer. The hammer falls and knocks the thumb safety down.

 

[batoy1911]

The thumb safety isn't being moved by pulling the trigger. The sear moves because the thumb safety isn't blocking it, and releases the hammer. The hammer falls and knocks the thumb safety down.

Aha! So it's simply the safety not blocking the sear?

 

[batoy1911]

Removed the sear & disconnect, held hammer back, inserted safety, eased hammer forward, hammer pushed safety off. Thanks, tuner...

 

[1911Tuner]

Yup. That's it. When the gun is completely assembled, the only thing holding the safety in the safe position is the plunger and detent. If the hammer gets loose from the sear, it'll wipe the safety off as easily as your thumb does.

 

[Quack]

 

[Hoxviii]

Yes, squeeze the trigger and the hammer starts to creep, then the thumb safety sweeps, trigger drops and the hammer falls full forward.

Well that answers it. It's just weird that it never manifest itself previously which is why I was wondering if anything in assembly could cause the issue.

Thank you.

 

[edSky]

Nice photos, Quack! A fully functioning (bits that count, anyway) cutaway version of a 1911 would be a great thing to have. I bet there would be a market (albeit a small one) for something like that. It would be worth a lot more than some DVDs. Just my 2 cents.

 

[Quack]

not my photo, just something that i have a saved the link to.

if you haven't seen this before
http://www.m1911.org/loader.swf

 

[David E]

The thumb safety doesn't prevent the trigger from moving...not directly anyway. The grip safety blocks the trigger. The thumb safety blocks the sear.

Correct. I answered the post just before bed! But at least I got the main part right.