BT & Thumb Safety Failure to work

[Manila's Finest]

Late last year I acquired an old, used norinco 1911-A1 at a great price. FREE! A X-mas gift from a friend. The gun was in pretty bad shape but it shot reliably to POA at 25 yards and is combat accurate. Also it feeds FMJs without fail. I decided to use this gun as my guinea pig to learn gunsmithing a 1911 with information I gained from this website.

I changed all coil springs with units from Wolff, installed a Wilson Combat trigger, a JTM S/S MSH, an STI sear spring, new wooden grips, a full lenth guide rod, Chip McCormick Hammer Strut, Jethro BT, and a Transmark hammer.

The hammer I got second hand (ever so slightly used) from an employee at a gunshop. All other parts were brand new.

Here's my problem: Now that I installed and fitted the new parts, the thumb safety and BT safety don't work correctly anymore.

If I pull the trigger without depressing the grip safety the hammer falls to half-cock. With the hammer cocked and the thumb safety engaged, the hammer pushes down the thumb safety and falls to half-cock when I pull the trigger. However it passes all other functions tests.

I am hesitant to test fire live ammo. I conduct all tests with Dry Fire Caps.

With regards to the BT grip safety, I thought I fitted it wrong (filed the arm down to much) but when I inspected it, the fitting seems to be okay (barely any trigger movement, at least same as before mods).

I also thought the Thumb Safety was worn but there's barely any movement of the trigger & sear (again, about the same as it was before the mods).

Don't forget this is an old gun that was really thrashed so there was some movement even before the mods were made.

I was really stumped so I re-installed the old hammer and everything suddenly worked fine again. I inspected the new hammer and noticed wear on the hammer radius above the half-cock notch where the sears rubs this surface. I compared the hooks on the new hammer to the old one and realized that they were pretty low compared to the OEM part. The shape is also much more square.

As mentioned before, I am new to gunsmithing (but I'm pretty mechanically inclined) so I'm not sure if I'm correct in assuming it's the NEW HAMMER that is at fault. Since it is a second hand unit in almost brand new condition, I'm guessing that a butcher of a gunsmith did a lousy trigger job and filed the hooks down too low so he couldn't use it for customer guns anymore. Then this jerk that works for him saw an opportunity and sold it to ME. Before I have a serious word with him or his boss for selling me a dangerous part, I'd like to be pretty sure it's not me who's directly at fault here. I know I should have inspected it better but I'm a novice at this and didn't know better at the time.

To more experienced gunsmiths:
Have you heard of or experienced similar things happening with hammers that have hooks filed down too low? Is my assumption correct or am I the BUTCHER here?

I would really appreciate any information regarding my problem.
Thank you in advance for your kind assistance.

Patrick

[John]

For grip safety: remove your thumb safety and your sear and disconnector. Then reassemble the pistol leaving these parts out, but insert the thumb safety from the right side of the frame, so that it keeps the grip safety in place. In that way, the opening on the left side of the frame is left open, allowing you to inspect the interior. Now, use a flash light to look in there and let the grip safety at its outmost position. Look inside the gun. The arm of the safety should be resting behind the trigger bow and should not allow it to move to the rear at all. If it is there but it allows the trigger to move, then you either need a new safety or you need to peen the arm a little to make it completely block the trigger.

For your thumb safety, a similar trick. Take out the grip safety and reassemble the pistol without using the grip safety. In that way the rear of the pistol is now left open so you can look inside. Look at the edge of the thumb safety where it touches the sear, when the safety is at its upper position. The sear should not move at all with the safety in that position. If it moves it at all, you need a new safety or again, if the movement is minimal, you can pin that part of the safety so that it completely blocks the sear.

One more thing, have you checked that your trigger allows your sear to fully engage with the hammer hooks? When you have the thumb safety out, do check that out.

[Manila's Finest]

Thanks for your reply John.

I've actually already done what you recommended. The thing is that my safetys work fine when I re-install my Government Hammer. I've burred it so it works with the BT.
I've compared the hooks on the new hammer to the hooks on my old hammer and realized the new ones are only half as tall! How much is too little?

Also when I do what you recommend I can see that the end of the trigger bow doesn't quite reach the place where the BTs arm comes down. The BT barely clears the frame (so its as long as it can be without getting stuck on the frame). Should I bend the end of my trigger bow where the BTs arm is supposed to touch it to get rid of the slight gap/movement?

Also since this is a really old gun, when i check for sear movement with the thumb safety engaged, it moves a little! It's my first 1911 so I don't know how much movement is tolerable. Like I stated before, with my old hammer, all is well.

The sear, and thumb safety are old and used with lots of wear and tear so it might be smart if I replace them anyway. However, do you remember Silverbullet from Sweden? I have a similar dilemna that imported parts are really expensive in the Philippines where I live. Think twice the US price. And salaries aren't that high as in the states or in Europe (where I used to live). I'm not sure I want to invest the money yet if I'm not totally sure that it's gonna cure my problem.

Maybe a new sear and thumb safety would be the right choice but I still have a real nagging doubt that the hammer hooks on the new unit are really just too short.
What so you think friend?

[John]

Before going to the gun, please edit your flag to reflect your country. A wrong flag is messing up our per country statistics.

On to the pistol.


I've actually already done what you recommended. The thing is that my safetys work fine when I re-install my Government Hammer. I've burred it so it works with the BT.


That's irrelevant. The old hammer sets the sear in a different way than the new one. The two parts (sear and hammer) are working together and it's after they are both in the pistol that the safeties are fit to them.

I've compared the hooks on the new hammer to the hooks on my old hammer and realized the new ones are only half as tall! How much is too little?


The hammer hooks should be between .025" and .030" deep.

Also when I do what you recommend I can see that the end of the trigger bow doesn't quite reach the place where the BTs arm comes down. The BT barely clears the frame (so its as long as it can be without getting stuck on the frame). Should I bend the end of my trigger bow where the BTs arm is supposed to touch it to get rid of the slight gap/movement?


The BT's arm should be able to move behind the trigger bow. If it does not drop down enough, you may have to file the protrusions at the bottom of the beavertail or at the top of the main spring housing (or both) so that the beavertail's arm comes further down to completely block the trigger. I am not sure I understand what you mean by clearing the frame etc. Maybe the arm is a little bend to the right?

Also since this is a really old gun, when i check for sear movement with the thumb safety engaged, it moves a little! It's my first 1911 so I don't know how much movement is tolerable. Like I stated before, with my old hammer, all is well.

With the slide on the frame and the gun fully assembled and the thumb safety in its up position, there should be no movement of the sear at all.

The sear, and thumb safety are old and used with lots of wear and tear so it might be smart if I replace them anyway. However, do you remember Silverbullet from Sweden? I have a similar dilemna that imported parts are really expensive in the Philippines where I live. Think twice the US price. And salaries aren't that high as in the states or in Europe (where I used to live). I'm not sure I want to invest the money yet if I'm not totally sure that it's gonna cure my problem.

Which sear and thumb safety are old? The one on the gun or the ones you are trying to install? I would not advise on installing used parts on any firearm unless you know very well what you are doing. I understand that the cost of parts is significant but it's your life which is at stake here.


Maybe a new sear and thumb safety would be the right choice but I still have a real nagging doubt that the hammer hooks on the new unit are really just too short.
What so you think friend?

I do not know if they are too short or not, I do not have the hammer in front of me. Use a feeler gauge and check them out. If they are at the measurements I gave you, you should be fine. From what I read in your repsonse, the sear is moving, so this is your problem. The safety is not blocking your sear as it should.

[Manila's Finest]

Hi John
First, thank you very much for taking your time to reply. I'm sorry about the confusion regarding my nationality. I'm half Swiss, half Filipino, grew up and studied in Europe and have now been living in the Philippines for about 8 years. I feel more swiss than filipino so I posted the Swiss Flag. I've already made the changes to reflect where I'm writing from. Sorry again if it screwed up the statistics.

Regarding the gun though, the BT arm does rotate nicely behind the trigger to block it. If it were longer the arm would catch on the frame while moving up when I depress the BT. It seems that the trigger bow is a bit to short or the trigger goes in to the frame too far. There is a small gap between the trigger bow in it's most forward position in the frame and the BT arm when it comes down to block it. That's why I was wondering if i should try bending the upper right side of the trigger bow (where the BT arm comes down). Im afraid though that it might interfere with the disconnector if I bend it excessively.

Regarding the sear and thumb safety (if I buy new units):
Am I understanding you correctly that I have to fit the lug on the safety (the one that blocks the sear) to the sear after I have installed a new one (sear) to the handgun? In other words my old sear and safety are fit to my old hammer and refuse to work with my new hammer?

I fully understand the functioning of all the parts on the 1911 but I have absolutely no formal training in gunsmithing in regards to this classic design. That's why I don't know the correct order of fitting parts to each other. However, I've read that one should change the sear when one changes the hammer but for financial reasons I tried to put off buying a new one. My mistake I guess. I really appreciate your help and will take your advice to heart. As soon as I can put aside the money I will purchase the parts and try fitting them.

I would be grateful for any advice you could give me in the future if I run into any new problems. Thanks for being a cool guy and helping me out.

[ArmscorBA]

Should have bought a Armscor pistol!!!!!! ;)
Sorry just had to say it!!!! :p :p
Ivan

[John]

Regarding the gun though, the BT arm does rotate nicely behind the trigger to block it. If it were longer the arm would catch on the frame while moving up when I depress the BT. It seems that the trigger bow is a bit to short or the trigger goes in to the frame too far. There is a small gap between the trigger bow in it's most forward position in the frame and the BT arm when it comes down to block it. That's why I was wondering if i should try bending the upper right side of the trigger bow (where the BT arm comes down). Im afraid though that it might interfere with the disconnector if I bend it excessively.

No, you should not bend the trigger bow to make it fit the safety.

You have changed a couple of parts in there, to be sure of exactly how to solve this. Do this test. Remove your new Wilson trigger and insert the trigger the gun came with. Check again the relationship of the trigger bow with the orgiginal grip safety. Study that "image" enough to impress it in your mind. Then put the Wilson trigger in and the new grip safety. Their relationship should be the same. It doesn't matter that much how far forward the trigger goes in the frame, what matters is that the little movement allowed by the gap between the trigger bow and the grip safety's arm, allows the hammer to fall.

Since everything goes back to normal, if the old hammer is installed, the problem is in the hammer/sear interaction. Try to find another hammer and see if it solves the problem, I do not trust Transmark's parts. Did you get the chance to measure hammer hooks depth? Or another sear. I do not know how close to specs is that sear you are using.

Regarding the sear and thumb safety (if I buy new units):
Am I understanding you correctly that I have to fit the lug on the safety (the one that blocks the sear) to the sear after I have installed a new one (sear) to the handgun? In other words my old sear and safety are fit to my old hammer and refuse to work with my new hammer?

The hammer/sear/trigger/disconnector all interact together. The safeties should be fitted to the pistol, after you have decided and installed these other parts in the gun.

[Manila's Finest]

It doesn't matter that much how far forward the trigger goes in the frame, what matters is that the little movement allowed by the gap between the trigger bow and the grip safety's arm, allows the hammer to fall.

Since everything goes back to normal, if the old hammer is installed, the problem is in the hammer/sear interaction.

You are absolutely correct! Even though I still do find the hooks on my new (used) hammer to be a little low, when I took a careful look at the tip of my sear I noticed that it's pretty worn out. The edge is more round than sharp.
I guess I really need a new sear for my new hammer.

I've learned something from you John. Thanks for sharing the knowledge.

I'm gonna try it out as soon as I can. However, I just got really busy at work and don't really know when I'm gonna have time for my hobby. For the moment I've re-installed my old hammer. All is well again with the gun. It just doesn' look as nice. Hahaha!

Should have bought a Armscor pistol!!!!!!
Sorry just had to say it!!!!
Ivan

Hi Ivan
I like Armscorp pistols too and plan on getting one soon. However the old norinco I have was for FREE! A gift from a friend for X-mas.

[John]

Time for me to move to Manilla and make some friends there!