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1911Pro.com • View topic - 1911 barrel upper lug fitting

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It is currently Wed Jul 18, 2018 3:56 am

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Joined: Thu Jul 31, 2014 10:52 pm
Posts: 76

Post Posted: Sat Aug 30, 2014 6:40 pm 
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Most "smiths" over here in Norway cut the hood until the barrel goes into lockup, without caring how many of the upper lugs actually have contact with the slide, and let the gun "run in". When I start talking about establishing contact on all three upper lugs, they tell me I'm dreaming up nonexistent problems, but the two guns I have let "professionals" fit barrels to, show a bit of play after years of shooting.(probably about 15 thousand rounds on the 45, and about 10 thousand on the nine.)

After seeing the pictures in Kunhhausen that describes how lugs can shear if only one of them are in contact with the slide, I decided to fit a barrel myself.
After loads of measuring, drawing and thinking, it took me several days of slowly filing, until I had close to 100% of all three upper lugs in contact with the locking surfaces in the slide. Then again, I'm no pro, so someone with more experience will do the job a lot quicker. This gun shows no barrel to slide play after about three thousand shots, will follow to see how it develops.

What I am wondering is how most barrels fit by good smiths over in the US are done, do thay take the time needed to establish 100% locking surface contact, or are they just letting the gun "shoot itself in"? Or am I just overly focused on unimportant details?


Last edited by evert on Sat Aug 30, 2014 9:36 pm, edited 1 time in total.
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Joined: Tue Mar 01, 2011 2:45 pm
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Location: Florida and Alabama

Post Posted: Sat Aug 30, 2014 8:04 pm 
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Pretty common here, too. Most who fit barrels don't own the measuring equipment/tooling to accurately measure anything except the first lug. More lugs bearing is always better and will result in a longer lasting fit. Especially true with the short guns and hotter calibers as they operate more vigorously than a simple Gov't length 45. For guys building super accurate bullseye guns, that's just one step in optimizing barrel fit for long term accuracy.

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Joined: Sat Nov 01, 2014 6:48 am
Posts: 21

Post Posted: Wed Nov 19, 2014 7:15 am 
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BBBBill, do most NM barrels have enough meat at the other two lugs to make full contact with the slide lugs? If yes, what does a smith generally do to relieve these oversize lugs, even when obtaining only first lug contact? Hope my question was clear...

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Location: Florida and Alabama

Post Posted: Wed Nov 19, 2014 4:12 pm 
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I don't fit enough barrels to speak with authority, but the two factors are accuracy of the slide lugs locations as well as the barrel lugs. The bullseye pros can probably tell you which slides are better/worse or more likely to have issues. Jerry Keefer has commented that the STI slides seem to be extremely well machined.
Fitting lugs is basically the same for all. Best done with the barrel accurately mounted in a lathe, but can be done with a safe side lug file and scraper. You're moving the vertical face of the lug instead of deepening. The goal is to get the front faces of the barrel lugs mating with the rear faces of the slide lugs. The trick is to accurately measure and map the slide (tricky without the proper tools) before you start cutting the barrel. Most folks start and end with the breach face to first lug and fit that, hoping for the best. Easy to do and it will work well for most purposes, but falls short when you're looking for the last gnat's hair of accuracy or longevity of fit in a gun that's shot a lot.

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Post Posted: Wed Nov 19, 2014 10:11 pm 
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Post Posted: Wed Nov 19, 2014 10:15 pm 
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And...after all this work is carried out successfully, what about headspace? Or is the breech closure what guarantees the headspace assuming a well fit barrel?

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Post Posted: Thu Nov 20, 2014 12:12 am 
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Post Posted: Thu Nov 20, 2014 12:35 am 
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Nice explanation. When it comes to setting headspace, I'm a little lost then on these EZ fit barrels I see, where you file down nubs. I imagine reaming for headspace is a critical operation...how does an EZ fit barrel eliminate headspace reaming from the process?

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Location: Florida and Alabama

Post Posted: Thu Nov 20, 2014 1:43 am 
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The EZ Fit is intended primarily for the hobbyist gunsmith and is different from a full gunsmith fit barrel. A bullseye smith would not use an EZ Fit. The "nubs" are simply raised pads left in the lug slots that reduce the amount of filing necessary to set depth of engagement. It is still necessary to check and adjust headspace as needed. Some are able to avoid reaming due to the way the barrel fits up to the average slide..... but not all. The 45ACP has the broadest acceptable headspace range of any round ever made, .898"-.920". Now no one building a gun is going to be satisfied with headspace at the upper end of the spectrum. Pro smiths all have their own target dimension based on their experience and the type of gun they're building/ammo they intend to shoot. A number I hear often is .905". The EZ fit is cut a few thousandths over minimum so that ,when the hood is shortened to fit the slide, headspace is still at or slightly longer than minimum and well under maximum. It is still a good idea to run a reamer in the chamber to verify that it was cut to spec in diameter as well as length.

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Post Posted: Thu Nov 20, 2014 2:11 am 
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Excellent! Thanks BBBBill!

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