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Thread: Stopping Barrel Fall At Linkdown

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  1. #21
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    NIEMi24s, I had a feeling that wasn't going to sound exactly right, but couldn't think of any way to sugar coat it. Sixty seven. Hope I can say that one day. I deal with a lot of customer modified things and know of what you speak.

    The experience you speak of with your Colt's barrel fitting, 42 years of reliable service, is what I would like to accomplish with the one I'm messing with now. I would like to have the frame, slide, link and barrel I am having to deal with be able to go the distance. If this requires a little machine work on any of these parts, so be it. A good trade off for reliability in my opinion. And my opinion is worth exactly what you paid for it.

    The only barrel I have seen with the bottom lug torn almost all the way off was a Kart. The tearout was almost complete with the exception of a small bit of steel in front of the lug holding the lug on. Kinda like the lug was sitting on an island. The tear did not extend into the chamber. I concluded that the bottom of the barrel feet were making contact with the VIS due to the gouges in the VIS and the peening of the back of the barrel feet. So perhaps any barrel can be destroyed with improper fitting.
    xxxxxx Iron bottom sez; Don't let your Rat Terrier hang around with college boys.

  2. #22
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    Quote Originally Posted by niemi24s
    Hi Tuner: Did the skid marks you refer to in Post #19, this thread, resemble those in Lazarus's pictures in Post #42 of his thread "Link Fitting - Voice Of Experience Needed"?
    No. Harder contact than that. Those appear to be normal contact marks.
    Use a piece of cold-rolled round stock to polish a like-sized radius in another piece of cold-rolled steel. It had a burnished, melted appearance...almost like metal had been transferred, except none had been.

  3. #23
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    Reliable Service?

    Hi Iron Bottom: Didn't want you get the goofy idea that I was some sort of whiz with the 1911. I'm just a shade tree gun plumber [and a lucky one too!]. After I got the gun (a cobbled together GI with a Union Switch & Signal receiver, Remington Rand slide and Colt GI barrel), I fitted a 1965 National Match barrel by H&R following the instructions in an article in the December 1963 American Rifleman and some other advise & tips. This work included a slide "squeeze job" and the initial peening down of the receiver rails. The rails have been peened down two more times, and have now been lowered and worn down about 0.008 inch below mid-spec. The receiver's top now looks like the top of an old anvil!

    I'm still trying to learn how the 1911 works and how to keep it working. This forum has been a real blessing in that regard, as the vast majority of my smarts about the 1911 have come from you folks. Thanks - to all of you.
    Last edited by niemi24s; 7th December 2006 at 16:10. Reason: Add Parenthetical Caveat


  4. #24
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    Hello First time poster.
    Does Anyone have any pictures to show on this very interesting subject? And exactly
    where the barrel lugs should rest on the pin?
    Thanks
    Sal

  5. #25
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    Barrel Marks on the Bed

    Folks,

    The photos I posted exaggerate the wear marks that appear on the bed. These marks are in reality extremely faint, but have caught the light just right in these photos to look worse than they are. In fact, these marks appear to me to be machining irregularities that have been left by the machine shop, and not by barrel banging. In any case I have shot maybe 150 rounds total in this gun!

    A question if you don't mind...would someone point me to the description of linkdown testing involving the slide stop? I gather that there was a post describing that the slide stop would be free to rotate if pressure were applied to the muzzle in linkdown. After careful testing, I see that my original assessment was incorrect. With the gun inverted, there is a slight hitch when pushing the slide back into battery. The hitch happens just at the point when the barrel's upper lugs need to engage into the slide. It is minor, but I feel it now. I was too aggressive before and did not notice. I'm wondering what part of the barrel camming is being tested when the gun is inverted?

    Thanks,
    Lazarus
    "Do not fix that which is not broken."

  6. #26
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    I hope Tuner, Lubaloy, and some of the other pros weigh in on this...meantime, go to the Schuemann barrel site and read the Timing Test Kit section - it's the best explanation of what should be happening, what can go wrong, and how to test for it that I've seen, it also includes the clearances he recommends, how to check them (you don't really need the kit), and how to get the clearances.

    But keep in mind that his is only one opinion, and some of the pros on this site seem to me to be satisfied with clearances (and methods for getting them) that differ from Schuemann.

    I think the Tuner recommended test of cycling the gun upside down is another way to remove any slack in the link as it hits the VIS. Similar to Schuemanns test 2.

  7. #27
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    Gun Upside Down

    So, holding the gun upside down and cycling (without recoil spring) primarily focuses on the slide coming out of battery...that makes sense. Is the slide stop test one of Schuemann's timing tests? It is hard to keep them straight. Pressing the muzzle against a table would force the barrel lugs against the VIS. However, the slide stop would not be free to rotate unless the link were totally unstressed at that point.

    -L
    "Do not fix that which is not broken."

  8. #28
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    Actually, I think it would check both going in and coming out - it removes vertical drop of the barrel due to gravity and allowed by link / pin slack, if any exists. When actually fired, things move fast and inertia will remove any slop, and this is a way to simulate that.

    But I'm guessing, Tuner is a true expert and will I hope he'll speak more to this. Also, some of the stickies address the issue.

    The free slide stop test is one of the 'false' tests Schuemann mentions at the end of the writeup if I remember right. If everything's perfect, the ss should be in slight compression at full linkdown.
    Last edited by gbw; 8th December 2006 at 10:00. Reason: Answer Lazarus


  9. #29
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    Loose Slide Stop Test

    Hi Lazarus:
    Ref: Your Q, Post #25, about linkdown testing involving the slide stop.

    1. The test method involves removing the recoil spring, plug, and guide rod, then reassembling the gun but with the slide stop lever hanging straight down over the trigger guard. Move the slide aft enough to unlock the barrel from the slide and then simultaneously push the barrel fully rearward (push muzzle against a table) and the rear of barrel fully down (push with finger through ejection port). Then, while keeping these two pressures on the barrel, see if the slide stop's lever is free to swing back & forth by flicking it with a finger and . . . . .

    A. If it does swing freely it means there is no pressure exerted on the slide stop pin by the link. This means the link is not in compression and the barrel's downward movement has been stopped by the barrel bed in the receiver (assuming it's not been stopped by interference with the slide's bore or the barrel feet bottoms contacting the receiver recess). Some people claim the barrel's downward movement should be stopped by bed contact. If the slide stop lever is completely free to swing under the test conditions the gun passes their test.

    B. If it does not swing freely and is quite hard to move it means there is pressure exerted on the slide stop pin by the link. This means the link is in compression. The barrel's downward movement has been stopped by the aft surface of the barrel's feet sliding down along the VIS until the link is squeezed between the slide stop pin and the barrel link pin/barrel. All this without the barrel contacting the receiver bed. Some other people claim the barrel's downward motion should be stopped by VIS/link in compression - with no bed contact. If the slide stop lever is not free to swing under the test conditions the gun passes the test of these people.

    C. The third possible outcome of this test is probably a fairly rare one. It's actually right in between A and B. The slide stop lever won't freely swing back & forth when flicked with a finger, but it'll move a little bit. If this is the test outcome, it means the barrel's downward movement has been stopped by both the VIS/link in (a little bit of) compression and the barrel bed. For those claiming the job of halting the barrel's downward motion should be shared by the VIS/link and the bed, if the slide stop lever's not too loose but not too tight, the gun passes their test.

    Bear in mind all this concerns testing for what halts the barrel's DOWNWARD movement. Its rearward movement should only be halted by contact with the VIS - and NOT the link in tension in conjunction with the bed.

    Got no idea (now) what's best - A or B. At present, my old target plugger meets the criteria in C! All I'm pretty certain of is that (based on Ordnance Dept blueprint specs), most USGI 1911A1's would have loose slide stops at linkdown and fall into para. A, above (See Post #1, this Thread).

    Hope I understood your Q correctly. Regards.

  10. #30
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    Tests

    To check for short link/VIS too far rearward/Lower lug too far forward...
    Push the barrel as far rearward as it will go against the edge of a table. The slidestop arm should swing free. If it doesn't, the barrel's rearward movement is being stopped by the link in extension. Bad juju. Baaaaaaaad JUJU!

    With the slide fully rearward, rearward pressure off the barrel...push it down firmly. If the slidestop arm swings free, the barrel's drop is stopped by the frame bed. If it gets into a slight bind, it's being stopped by the link in compression. Check to see how FAR off the bed the barrel is stopping. More than a thousandth or two...or more than a slight bind of the slidestop pin is bad juju, but easily corrected.

    Stopping the drop on the link in compression is rarely seen anymore, except in a very carefully fitted pistol...and few of those do. Most stop on the bed. As long as they don't hit the bed first or at the same time...Heap gooooood medicine. The barrel should stop against the VIS near the radius at the top of the lug and drop the last couple of thousandths to bed. The farther down on the lug the impact is focused, the more likely you are to have a lower lug failure. This is the reason for the bowtie cut. It's not to correct a timing problem wrought by the VIS too far forward. It's to get the impact stress off the lower lug feet, and is unnecessary if the VIS is within spec...and is generally done as more of a preventive measure than out of necessity. In any event, the cut shouldn't be more than about .003 inch deep...IMNSHO.

    At the point of impact with the VIS, sufficient clearance should exist between the top of the barrel and the slide at the proscribed .250 inch of slide travel. It can occur a little earlier...but should occur no later.

    Bedtime!

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