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Thread: M1911-AI FS slide lock

  1. #1
    Join Date
    7th May 2021
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    M1911-AI FS slide lock

    New member Murray here with a little about my brand new as of April M1911-A1 FS GI. I'm trying an edited down version after my first draft started looking more like an essay than anything else. And yes, this is the short version (sorry in advance).

    Condensing everything down to what matters, 1)a big thank you to Terry - legendary Armscor customer service confirmed. 2)thank you all for your posts. I've been reading for a few months now and this is a real treasure trove for those of us who shun social media. I look forward to our conversations in the future and I already miss those of you I suspect I won't meet in this life.

    Now down to what I'm seeing. I was getting failure to lock open on the last round with my factory mag. I got a Kimber Tac Mag that worked more often than not. The WC 47D I bought and the CMC 10 rounder I borrowed shortly afterward wouldn't even allow the lock to lower and load the first round.

    One excellent interaction with Terry and a new slide lock in the mail to try, I can get all 4 mags to load up round #1 just fine, and I'm at least mostly locking open on the last round. I'm guessing the remaining issues could still work themselves out over time.

    My last observation is thanks to a new digital gauge. The factory lock comes in at 1.3665" end to end, while the new one is an ever so slightly shorter 1.3535". I also noticed last weekend that the WC and CMC mags have slight gouges I'm sure the original lock caused (pic on the WC mag att'd if I can figure that out).

    WC_47D_slide_stop_gouge.jpg

    So what do y'all think? Did I get it pretty close, have you seen this before? Any pointers for a novice? Thanks in advance. Feel free to move - I read the posting guidelines and hope this is RIA specific enough to belong here.

  2. #2
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    Seeing rounds catch the slide stop as they feed is usually caused by the profile of the slide stop lug, not the length of the slide stop. That would not, however, prevent the slide stop from locking the slide open on empty. That's generally either weak mag springs, or some kind of a burr that interferes with the free travel of the slide stop.

    Have you done any more shooting? Do the problems still persist, or have they been cured?
    Hawkmoon
    On a good day, can hit the broad side of a barn ... from the inside
    Likes (1) :
    Rick McC. (21st June 2021)


  3. #3
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    I managed to get out the last couple of weekends and the Rock seems to be improving, mileage ~550 rounds. I had a few failures to lock over those sessions, which I count as a step in the right direction. In a way I suppose I'm only investigating after reading so many posts from other owners claiming thousands of rounds with absolutely zero issues.

    I managed a full on jam if I understand the term correctly. The round was stuck at about a 45 degree angle and slide half open. I was a little too surprised to look closely for exactly where the round was stuck. The magazine was a little tough to drop. When I got it out, the round finished chambering. I cycled the action to be safe, but I think it would have fired just fine.

    I'll see what I can do about checking for burrs. I suppose a weak mag spring might be going on, though all except the borrowed one are brand new. Reading around here is making think a Checkmate is a good excuse to do some shopping. If anything, thinking springs sends me back to the break-in hypothesis and say the recoil spring has some teething to do.

    I still suspect two or more problems. More "research" is necessary, which won't make me sad at all. My hope is the slide stop was the main culprit. Someday I plan to swap it back in and see if some of the old problems come back. I do see some copper on the inner surface of both the old and new stops, which like your observation above is another thing that would point me in the opposite direction to premature slide locks. I did have one several weeks ago. The RO also suggested tapping my magazine to seat everything well to the back like a pack of cigarettes, which was probably my issue then.

    All in all, I hope at least describing what I'm seeing will help someone else who sees something similar. I haven't been through every post here, but so far I haven't found anything that matches exactly.

    Thanks for getting back to me. After reading so many of you posting over many years, you already seem like old friends.

  4. #4
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    Tapping the magazine to move all the rounds to the rear is always a good idea ... but after one or two sots, recoil may undo all that precaution.

    If your slide stop lug shows copper deposits in the area shown below, it's time to break out the half-round file and do a bit of judicious adjusting:
    Attached Images Attached Images
    Hawkmoon
    On a good day, can hit the broad side of a barn ... from the inside
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    Rick McC. (21st June 2021)


  5. #5
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    Quote Originally Posted by Murray View Post
    I managed a full on jam if I understand the term correctly. The round was stuck at about a 45 degree angle and slide half open. I was a little too surprised to look closely for exactly where the round was stuck. The magazine was a little tough to drop. When I got it out, the round finished chambering. I cycled the action to be safe, but I think it would have fired just fine.
    This condition is commonly called a Failure To Return to Battery, or FTRB.

    Because there are so many reasons for an FTRB, it's important to stop and analyze the situation and not try to clear the jam and keep on shooting. Here's something to use in gathering the information we need to help solve this problem:

    https://docs.google.com/document/d/1tY9zX-F_dWgxMstQAC-cbfKraO_Tmc6FiaDzaEMvECs/edit?usp=sharing
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]

  6. #6
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    And here's the image that was supposed to appear in paragraph 13:

    P(09)8230012a Series 80 Super vs. Gold Dots, Post 8.jpg
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]

  7. #7
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    Back to the slide stop (SS) issue.

    The arrow in your photo shows the aft end of the SS contacts the magazine tube. In order to do that, that portion of the tube must be forward of the dog house shaped frame cutout for the SS. None of my magazines will go far enough forward for that tube surface to protrude into that hole. Army Ordnance specs show the distance from the forward surface of the SS pin hole in the frame back to the aft surface of the dog house hole (slanted forward at 4 from the vertical) should be between 1.3085" and 1.3175". My wadcutter gun measures 1.311" using the ID nibs of vernier calipers.

    Strip the frame down far enough to push the SS plunger back into its hole and use the ID nibs of your calipers to measure from the forward part of the SS pin hole to the aft surface of the dog house hole. Your calipers should be 4 from "horizontal" if your dog hose hole has the 4 slant.

    Q1: What did it measure?

    [both of those measurements given for the overall length of the SS arms are within spec, but don't mean much. Distances from the SS pin are the important ones.]
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]
    Last edited by niemi24s; 10th June 2021 at 22:27.


  8. #8
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    And as pictures speak louder than words,
    M1911 Dog House Hole.png
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]
    Last edited by niemi24s; 11th June 2021 at 15:13.


  9. #9
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    Wow, all of this is great information, thank you both. I'll take some time to digest this. So far I see a trip to Harbor Freight for the famous needle files I've been reading about and some quality time with my gauge this weekend trying to figure out if something other than me is out of spec.

    This might sound a little counterintuitive, but if the slide measurement above looks okay, I plan to try shortening the old factory slide stop to see if I can get it to fit better. It might be good practice before I mess with the one that mostly seems okay. Plus my best case becomes two mostly working stops instead of one long one and one badly mangled one.

    And if I do get another FTRB or other malfunction - I'll take a closer look instead of fearing some vague catastrophe. I might wait a minute before sticking my face up close to a small explosive where it shouldn't be, though.

  10. #10
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    Quote Originally Posted by Murray View Post
    And if I do get another FTRB or other malfunction - I'll take a closer look instead of fearing some vague catastrophe. I might wait a minute before sticking my face up close to a small explosive where it shouldn't be, though.
    No need to wait. If you have an FTRB, the gun hasn't returned to battery and the hammer is still cocked. Just grab your cell phone (to take the picture) and your magic marker (to mark the top of the jammed cartridge).

    Marking the top of the cartridge makes it easier to locate the flat spot on the underside of the bullet. Measuring the angle of that flat spot will allow the determination of where the bullet nose hit the frame feed ramp when it was being stripped from the magazine as the slide tried to return to battery. Here's how I do it:

    P(11)1070025 Angle Of Nosedive..., Post 1.jpg
    When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]
    Likes (1) :
    Rick McC. (21st June 2021)

    Last edited by niemi24s; 11th June 2021 at 15:32.


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