1911 firing to half cock...need some help

[walt o]

take the barrel out of the gun ,hold it pointing down at floor and drop a live round into chamber .It should go PLUNK and seat flush with the back of the barrel hood .
That's the drop in test.

 

[baba]

Today I sat down and messed with this some. I checked the following:
1. Grip safety clearance - looked good. No signs the trigger was contacting the rear/lower lug of the GS extension, so the trigger can move freely to the rear.
2. Overtravel Screw - with the trigger depressed the sear clears the hammer such that there is no perceptible friction between the two. I take this to mean the setting I have on the screw is good. With the screw in either position ('normal' or out two turns) I could not recreate the problem without pinching the slide to the rear.
3. Thumb safety clearance - The thumb safety clears the sear with no perceptible movement. I marked it with a marker and checked for rubbing. I also tested several times with the thumb safety removed and again, could only make it happen with the slide pinched back just a hair.
4. Barrel lug fit. I marked this as well, and found there were no odd wear signs. The take down pin/slide stop was riding evenly on both lugs. The top lugs fit ok as well, with no strange markings showing up there. The barrel hood did show some signs of rubbing the breech face evenly across it's width. I looked back in the Kuhnhausen book at his procedure for fitting the barrel hood and all he calls for is to remove material from it until allows the barrel to be fully seated in the top lugs. Mine does this, so I'm inclined to think this is OK. Does anyone have any wisdom on how much/if any clearance there should be on the hood to breech face?
5. Headspace - the barrel does pass the drop in test. Barely. I can't for the life of me find my headspace gauge, but when I measure with my caliper from the shoulder at the end of the chamber to the back of the hood, I can only get about .891. The min spec in the book is .898. Since I have virtually no clearance with the hood and breech face, I'm thinking this could be the issue. I need to find that gauge...

-Brian

 

[AllenM]

If you had to remove hood material .010 to fit the barrel it is likely you will need to recut the chamber a little deeper that may solve the issue of the gun going in to battery. hood clearance should only be a approx .002 but when you shorten the hood you shorten the chamber so I would look at that. are you getting .045 is barrel engagement into the lugs? one more thing you should check if you haven't
Still though the hammer should not drop to the second notch, this sounds like a separate issue. Disconnector? maybe but even though it sounds like you have thoroughly looked everything over I still have reservation. could be though

I did fiddle with one of my 11911's to see if I could reproduce your symptoms and I actually was able to do it once, but I had to move my slide back about 1/8" or a little more to were I could feel the disconnector engaging but I could only do it once were it was right on the edge of the sear and fell off before the hammer could fall all the way. if you have other 1911's compare with maybe check where the disconnector tunnel and groove in slide are cut at to see if there are any differences. maybe but maybe the groove in the slide is off?

 

[baba]

Let's talk about that disconnector. I have checked this out extensively. When the grip safety is off, I can see exactly what is going on. Only the very top of the wings of the disconnector that engage the sear are in contact with the lugs on the sear. When the slide is fully forward, it fires just find. When it is rearwards just that hair, the disconnector is pushed low enough that it starts to engage the sear, but when the sear swings far enough it slips off the bottom. Thus, the hammer falls but the sear starts to reset and it ends up in half cock.

I hope I have described that clearly enough. This has led me to think that
1) my disconnector is too long
or
2) the slot in my slide where the disconnector sits in battery is too shallow. I have checked that it is in the correct position front to back, but the drawings don't show a depth. I assume if the position and width of the hole are correct, they must have used the proper diameter cutter and gone to the proper depth, but it is an assumption at this point.

I have been afraid to shorten the disconnector, or deepen the slot in the slide until I got some advice on what may be going on there. At this point, I know the mechanics but need to figure out what I need to do to fix it. So...any advice?0

I will try and get a picture of the slide in the proper position to make this happen, and I do have access to another 1911 that I can use to compare. I'll get that stuff up here as soon as I can.

Thanks,
-Brian

 

[IndyGunworks]

When the slide is fully forward, it fires just find.

When it is rearwards just that hair, the disconnector is pushed low enough that it starts to engage the sear, but when the sear swings far enough it slips off the bottom. Thus, the hammer falls but the sear starts to reset and it ends up in half cock.

Its doing EXACTLY what its supposed to be doing, the way its supposed to be doing it. Preventing an out of battery discharge.

Figure out whats keeping the slide from going ALL the way forward and you have found your issue.

Could it just be break in maybe? How many rounds do you have through this?

 

[baba]

Ok,

Here it is IN BATTERY


And here OUT OF BATTERY


The difference in the gap from the slide rail to the back of the slide is about .010-.012. That's what it takes to get it to fail. I agree that it is doing what it should be doing - preventing an out of battery ignition, but what I'm not clear on is - is it really out of battery? Or is something wrong with the geometry of the disconnector or slot in the slide that is making it act like it is out of battery when it isnt? I need to find my gosh-forsaken headspace gauge and test that as I believe that may be a problem, but I'm not sure if it is the only problem. Though I guess also that if the slot in the slide is in the right place, and the disconnector is in-spec then maybe the geometry isn't an issue. What do you guys think? Is there a spec on how much of the disconnector wing should be in contact with the sear lugs when in battery? That may give me an idea of whether my in spec disconnector is just a bit too long for my particular set up.

-Brian

 

[baba]

Oh, and I'm somewhere between around 500 rounds fired at this point.

-Brian

 

[IndyGunworks]

I gotta say I am stumped on this one. My gut tells me that shorting the disconector just a tad to fix THAT 10 thou wouldn't hurt anything, but at the same time it tells me that's not the right thing to do.

If this were me, and not being able to test it in this cold, I would fill the whole thing up w/ lapping compound in all the suspect areas including guide rails, and FCG and cycle the hell out of the gun and try to slick things up a bit.

Do you have the ability to try an higher weight recoil spring?

I have the gauges, but am not in the NW.

 

[IndyGunworks]

with 500 rounds through it already I don't think lapping the suspect places will do you much good.

 

[ghitch75]

are your rd's flush or just below the hood?......i seen in one of your other posts your hood was tight?......if so that throws the head space off too......a few rd's fire and it gets warm and makes is worst......

 

[baba]

Hood is tight to the frame. Loaded ammo drops in just flush with the back of the hood, but I cant find my go-gauge to check it again. I'm thinking this may be part of the issue..if my chamber is about .010 short as I measured, and that's about what it takes to knock it out of battery...it adds up. I hope to check a few things against another 1911 later this week and will report back. May have to buy a new go-gauge. My advice...never move. You lose your stuff when you do.

-Brian

 

[baba]

I mean hood is tight to the slide. It just brushes it...haven't put a feeler gauge in there yet.

 

[drillsgt]

I read through this thread trying to understand if you were having hammer follow issues or not but I think I understand what you are saying. You are saying that with your slide fully closed it functions as it should but with the slide pulled back that tiny bit it still fires? That's normal if that's the case. That insignificant amount is not enough to deactivate your disconnector. Sounds like you need to keep breaking it in and it's still a little tight. If you think you are pretty much maxed out in your upper lugs you could polish your lower lug a tad and probably take care of it. If it will lock up normally but ocassionally the slide doesn't close up all the way it's likely not a headspace issue. How's your extractor tension?

 

[baba]

You are correct, except it fires to half cock when the slide is back a tad. That is not normal. I will add checking the upper lug engagement again to my list. At one point I had all these numbers written down, but in a recent move I haven't been able to locate everything yet.

I beleive I may have a headspace issue, based on the measurements of my chamber that I took. Since I can hand cycle the gun all day and not recreate the half-cock firing problem (that is, it only happens with real ammo present), I think that may be what is causing the issue. A longer round goes in, it bumps the slide back that hair, and I get a fire to half cock....

So I need to find or replace my go-gauge and see if that is a problem or not. If it is, I fix it and see if the problem re-occurs. If it doesn't grand. If it does, then..well that is why I'm still looking for things to double (triple, quadruple, pentuple) check.

-Brian

 

[drillsgt]

You are correct, except it fires to half cock when the slide is back a tad. That is not normal. I will add checking the upper lug engagement again to my list. At one point I had all these numbers written down, but in a recent move I haven't been able to locate everything yet.

I beleive I may have a headspace issue, based on the measurements of my chamber that I took. Since I can hand cycle the gun all day and not recreate the half-cock firing problem (that is, it only happens with real ammo present), I think that may be what is causing the issue. A longer round goes in, it bumps the slide back that hair, and I get a fire to half cock....

So I need to find or replace my go-gauge and see if that is a problem or not. If it is, I fix it and see if the problem re-occurs. If it doesn't grand. If it does, then..well that is why I'm still looking for things to double (triple, quadruple, pentuple) check.

-Brian

Okay, so a deliberate pull of the trigger with the slide back that little bit and it only falls to half cock?

 

[ghitch75]

not going into full battery will let the diconnector engage enough to catch the half cock notch.....

 

[baba]

Drillsgt....correct.

Glitch, yes. So what I have been trying to figure out is

1. Is it actually in battery but having this issue anyway...which would mean a problem with the disconnector or the relief for it on the slide

Or

2) what is preventing it from going in to battery.

To those ends I still Need to check head space and barrel lug engagement. I may also try a heavier recoil spring. I will also check the disconnector geometry compared to another 1911 when I get a chance.

Brian

 

[AllenM]

This may sound silly but how does the safety look in relation to the notch in the slide when its engaged. Does it look like the slide could stand to go forward even with the gun in battery? the little hanging over on the end doesn't mean much but if the slide did go forward that amount the disconnector would probably be in a deeper part of the channel.

 

[wolfman]

I'll add another silly question. How tight is the barrel bushing? Tight enough that if the barrel expands from the heat of being fired, that it becomes tight enough to bind up the slide ever so slightly at the end of its travel closed?

 

[baba]

A few updates:

I confirmed that I have .046 engagement of the barrel lugs, which is greater than the minimum .042.

Here are two pictures showing the safety notch in the slide





The position looks OK to me.

I got another 1911 (factory gun) to compare to.

I measured the depth and length of the slots on the two slides. Here is what I got

Factory gun/My hand built
Depth: .064/.062
Length: .040/.039

So I guess my slot depth is OK after all. Grr. I was hoping that was it.

Here is the interesting part. I measured the portrusion of disconnector above the frame, and here is what I have:

Factory gun: .053
My Hand made: .060

So the disconnector is almost on size with the slot. I know I measured it before I put it in and confirmed it was within spec, but I want to pull and measure it again. I'm just too cross eyed right now from a long day at work. It also has a more square profile than the factory gun's part.

My final observation for the night is the factory gun has a lot more tension on the disconnector. I may have to try that as well.

Does this info spawn any other ideas guys? I'm too tired to think...

Oh, and the bushing was fit to the barrel by Kart. It is tight but there is some perceptible movement. It fits pretty tight to the slide but I don't believe it is binding at all. I get no signs of springing or anything in the groups I shoot.

-Brian