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Thread: Stopping Barrel Fall At Linkdown

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  1. #11
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    Info For Laz & Q For Tuner

    Hi (again) Lazarus: Here's another writer who calls for the barrel to seat on the receiver bed; Mike Watkins (Brownell's) in the 17th paragraph of "Building A 1911 - Part III" in the Technical Issues section of the Gunsmithing part of this forum.

    Iron Bottom, in Post #5 this thread, thinks he saw it one of Kuenhausen's books. Don't have any of J.K.'s books (yet), so I really can't say.

    FWIW:my simplistic thinking on this subject is it'd be best to stop the downward movement by barrel/bed contact. These two surfaces would seem to be able to withstand the impact - however much impact there is - a lot better than having the link transfer it all to the slide stop pin and its holes in the receiver.

    Tuner, in Post #2 this thread, says it's OK for the barrel to contact the bed as long as its rearward motion has already been halted by the VIS. How can I tell if the barrel contacts the VIS before it contacts the bed when the gun is fired?

  2. #12
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    In Kuhnhausen's Vol 1, page 65 under Mating Check and page 66 under Bottom Lug Rear Adjustment, there are these procedures for barrel and link fitting. Reads, to me, like the barrel lower lug should not contact the frame. Sure would simplify things to only have to remove a little material from the rear of the lower barrel lug. Getting the barrel to stop on the lug .001 above the frame is a delicate operation. But Tuner as well as Shuemann recommend stopping the barrel on the lug and VIS and it is hard to argue with their reasons.
    xxxxxx Iron bottom sez; Don't let your Rat Terrier hang around with college boys.

  3. #13
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    Hi Iron Bottom: After reading through Shuemann's materials several times it occured to me that (as a maker of barrels) he'd be naturally reluctant to instruct the general buying public to remove metal from the aft vertical surfaces of the barrel's feet. This cuz if not properly done, and the radius at the top is removed by an uninformed "filer", a good starting point for a crack at the feet/chamber junction will have been created by the sharp corner.

    Shuemann's instruction to move the VIS aft seems a poor choice to me for another reason. Why diddle with the VIS in the receiver (the most expensive part and perhaps the longest lasting part) to make the barrel fit, when the next barrel that gets installed may be some other brand. Could be the VIS might need to get moved forward to properly fit this barrel, and the shade tree gun plumber is in a real predicament.

    Moving a VIS back is difficult enough, but moving it forward would involve (I think) welding it up and then having to dress the weldment back to fit!

    I also think of the consequences of messing up what I'm working on: do I want to mess up a barrel or a receiver?

  4. #14
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    Smile

    Well, for one thing, I have had several conversations with Wil Shuemann and I do not think he would give anyone misleading information. The next barrel? I'm sixty years old. I don't worry about the next barrel. Or frame.
    xxxxxx Iron bottom sez; Don't let your Rat Terrier hang around with college boys.

  5. #15
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    Hi Iron Bottom: Didn't mean to imply Shuemann's information was misleading. As a mater of fact if I put myself in his shoes I get the heebie-jeebies just thinking of somebody filing the back of the feet, not keeping the radius, and having the feet crack & separate from the barrel - a barrel I (Shuemann) made! (I've heard this can happen)

    I've only hard fitted one barrel, did it about 42 years ago, and am pushing 67 years of age. Still have and shoot this old GI 1911 (my one and only 1911). I'm just saying if I ever hard fit another new barrel (even one of Mr. Shuemann's) and need to either file the feet or VIS to get it to work, I'll file (carefully, keeping the radius like I did previously) the feet first before even thinking of moving the VIS back. This is partly because the VIS in my gun is about 0.005 farther back than the upper specification limit.

    I've got a spare barrel (such as it is), but no spare receiver.

  6. #16
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    The only way the barrel can stop on the frame bed instead of the VIS is if it is stopping on the link.
    Any contact with the frame bed should be minimal and occur after contact with the VIS.
    Link length will determine proper distance from the slide stop pin to the VIS. If this needs correction, best to remove material from the rear of the barrel's lower lugs, if the VIS is correctly located.

  7. #17
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    re:

    Filing on a VIS to move it back gives me the heebie-jeebies. Too easy to cut it at an angle and leave the lower area sitting too far forward. Not the place that you want the tips of the lug feet to smack.

    Lub...I've seen two barrels that hit the bed hard just before or just as they hit the VIS. Neither were stopping on the link, and both pulled through the chamber floor with a spread-legged "U" shaped crack...wider at the back. The lug wasn't separated from the barrel at the rear...but another 100 rounds probably would have done it. Both were mid-production ORM Colts. Rare...but it can happen. Tolerances stacked up in the wrong direction.

  8. #18
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    Tuner,

    Stopping on the bed would put less pulling force on the lugs, no?
    Usually when a bbl fails in this manner it is due to lack of the VIS relief.

    Interesting that Schuemann notes that failures of this type are not uncommon with 416S steel due to sulphur stringers.......the very material he uses for his barrels.

    Also interesting that Springer 2 pc bbls exhibit the most common lower lug pull-outs, yet Springer frames commonly lack the VIS relief.

    I've seen more than a few IPSC 38 supers bbls shear the lower lugs completely off! Most, but not all of the time, this was attributable to improper linkdown.
    I've never seen a forged chrome-moly Kart fail like this, even improperly fitted.


  9. #19
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    Quote Originally Posted by Lubaloy
    Stopping on the bed would put less pulling force on the lugs, no?
    Usually when a bbl fails in this manner it is due to lack of the VIS relief.
    Probably...but here's what I found in both cases.

    Very small amount of clearance when in bed. Something on the order of .007 inch, IIRC. There was no visible damage to the front corners of the upper lugs, as is often seen with timing issues. The rear of the lower lug was also undamaged, which indicates that there wasn't a problem with the barrel getting caught between slide and VIS. The chambers didn't fail at the rear junction of lower lug and barrel. It was slightly forward of the rear of the lug...about 1/8th inch or so. There was no peening evident on the VIS, nor was there any indication of hard contact at the lower lug feet on the VIS.

    There was evidence of hard contact at the frame bed and lower barrel radius in the form of deep burnishing that almost looked like skid marks. Odd...

    There was evidence of scuffing on the tops of the upper lugs and hood area, which I figured to be coming from the barrels just narrowly clearing the slide as they linked down.

    The VIS in both guns were slightly rearward of mid-spec...but still within tolerance.
    The field-test for stopping on the links produced a completely free-swinging slidestop pin on one, and the tinies bit of bind on the other. I could move the slidestop arm with a light flick of a fingernail...so on that one, the barrel was stopping on the VIS, but still had the link and crosspin in light tension...very light, and not enough to stress the lower lug.

    Neither link had been stretched...but both were shorter than the standard .278 when measured across pins. Both were about .003 inch short, but again...neither was in hard tension when the barrel was fully down. Flipping the guns upside down and racking the slides produced a slight hitch at the linkdown points tha wasn't apparent
    with the guns rightside up, or tilted dhown at 45 degrees. Only when held upside down. The hitch was very slight.

    Assessment was that the barrels were hitting the beds at the same time, or possibly slighty ahead of hitting the VIS. A check of the bed height to the frame rails showed both to be slightly higher than mid-spec, though both were within allowable tolerance. With perfectly clean guns, the drop timing probably wasn't an issue. When a little carbon built up on the bed, it likely brought on the stresses that did the barrels in. A quick barrel switch from two of my Colts gave the same indications of a problem there, since all dimensions were virtually identical. The owners wanted to replace the barrels with OEM Colt barrels, and I ordered the parts...along with Wilson #3 links...and replaced the barrels.

    To prevent a repeat of the barrel failures, I deepened the beds in both frames to provide .015 inch of drop clearance with the slides. Both guns have been chuggin' along for about 5 years now under fairly heavy use, and the barrels are still good.

    'Bout all I can tell ya...

  10. #20
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    Skid Marks

    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"?

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