Building a 1911: Fitting the Barrel and Slide

The last time I tried to fit a 1911 barrel to a slide and frame it took a great deal of time and effort, mostly due to efforts to go cheap. The inexpensive barrel used for the first attempt required extensive filing of rough edges and casting seams, needed reaming and headspacing despite being ostensibly “drop-in”, and ultimately had to be discarded due to a void in the chamber. Its replacement, the optimistically-named Kart EZ-Fit barrel, required time-consuming (but EZ) fitting, also needed to be headspaced, and was fairly expensive to boot.

This time around, I cut to the chase and just started with an expensive barrel. In fact, the barrel was pretty much guaranteed to be expensive, since I wanted a threaded barrel so that the 1911 could be used as a silencer host. Grabbing a Storm Lake stainless steel threaded barrel on sale managed to cut the cost slightly; as an added bonus, it was advertised as drop-in, which provided a great excuse not to fit a barrel.

Naturally, the barrel required some fitting. The first and most obvious sign of this was the bushing tab not fitting into its recess in the slide. Eyeballing the difference showed it to be a pretty near thing, and using Dykem confirmed that observation.

I hit the edge of the bushing tab with a safe-edged pillar file just to get an idea of how much metal would need to be removed, only to discover that the tab started going into the slide’s slot immediately. It only took a few more strokes with the file before the bushing would fully engaged with the slide, albeit requiring the help of a bushing wrench. I don’t like needing a tool to field-strip a gun, so I applied some lapping compound to the tab and twisted the bushing back and forth until it required only some light swearing to remove by hand.

A correctly oriented bushing is prerequisite for fitting the rest of the barrel because the hole through the bushing is (or should be) slightly angled to permit clearance during link-down; a tightly fitted barrel with a dimensionally correct bushing will bind slightly if you try to cycle it with the bushing upside down. For this reason, the bushing has to be the right way up in order to assess how the barrel will fit under normal operating conditions.

More importantly, though, it finally allowed me to assemble the slide and hand-cycle the action. It was a satisfying milestone, but also revealed a couple areas which needed fitting.

First, the barrel didn’t drop very far on link-down. Cycling the slide produced a distinctive zipping sound from the hood and lugs dragging on the interior of the slide, and drag marks were also visible on the hood itself. At link-down, the clearance between the hood and slide interior was less than 0.003 inches; Kuhnhausen recommends 0.010 inches for a duty pistol.

Second, the breech end of the barrel hood dragged on the breech face, leaving a faint polishing mark. It was the work of moments with a file and some stones to get rid of the drag, allowing final barrel link-up position to be solely controlled by what was happening inside the slide. But what was happening inside the slide? Lacking x-ray vision, I turned to the next best things: Play-Doh and lipstick.

The Play-Doh was for figuring out how deep the locking lugs on the barrel engaged with the corresponding recesses in the slide, and how many of the lugs met up. Although modern steels will let 1911s get away with surprisingly little in the way of lug engagment–both in the number of lugs locking together and how deep they lock–it’s good to know what one is dealing with. Kuhnhausen recommends using modeling clay, but I use Play-Doh because a) it comes in various neat colors, b) it smells nice, and c) I don’t have modeling clay.

The graphite prevents the Play-Doh from sticking to the interior of the slide, reduces tearing when retracting the slide, and makes a terrific mess. Still, you can’t argue with results.

First, the depth of engagement was good. The lugs themselves measured 0.051 inches deep. Careful eyeballing with a depth gauge and Play-Doh contact suggested about a 0.047 inch engagement on all lugs–not bad at all. The first lug looked like it was in contact, and maybe the second. The third lug was dubious, but things may change after the first time they sustain several tons of pressure.

Note that in the above photo it looks like the Play-Doh impression is slightly off-center. I think this is because of uneven Play-Doh application, but if barrel or slide lugs are canted, there’s not much I can do about it with these parts. The standard approach to adjusting barrel cant consists of removing material from lower lugs and/or the edges of the rear barrel hood; however, this pre-fit barrel has no extra meat to work with. Given that there are no other indications of a canted barrel such as uneven wear marks on the slide stop pin or the barrel hood dragging against one side of the slide, it looks most likely that Play-Doh was simply applied with insufficient rigor.

Next up was fixing the clearance between the barrel and the inside of the slide when linked down. As mentioned previously, the clearance was insufficient and the barrel hood and lugs rubbed on the inside of the slide. Far from being a mere fitment issue, rubbing indicates several potential problems. In order of increasing badness:

  1. Friction between the barrel and slide slows down and can disrupt slide cycling.
  2. Barrel and/or slide lugs can become rounded or flanged through edge contact with their counterparts.
  3. If clearance problems are caused by stopping on the link, then firing it without fixing that will eventually tear the bottom lug off the barrel or break the slidestop pin.

That last bullet point needs more explanation, but since it turned out to be related to the cause of the clearance issues and I took photos while fixing it, I’ll explain as we go.

Sometimes barrels don’t clear the slide enough because they don’t go down far enough. To continue in this vein of brilliant insight, barrels don’t go down all the way because something is holding them up. I can think of five ways the barrel could be prevented from going down:

  • Recoil spring guide holds the barrel up due to dimensional problems with the guide and frame.
  • Bushing hole is bored incorrectly and doesn’t let the barrel tilt.
  • Barrel cutout in slide is too tight (or barrel too fat) and the slide holds the barrel up.
  • Barrel feet don’t have enough clearance for the link and it binds near the end of its travel.
  • Frame bridge doesn’t let the barrel link down far enough.

Note that all of the above assumes that the slide and barrel are correctly dimensioned, and the slide correctly fitted to the frame. If the barrel is too tall or the frame too short, or the slide fitted to the frame too low, then none of the above could apply and there would still be clearance problems. In those cases, though, the solution consists of throwing out or machining the frame and/or slide.

Fortunately, the cause was among those in the list above. I started with the assumption that one of the issues from the bottom of the list was the most likely and began diagnosis accordingly. The first step was to apply lipstick.

To the barrel. I applied lipstick to the barrel.

One could use contact marking fluid, but I don’t like the stuff because it flows a little too easily and stains like crazy. Lipstick is just as messy, but it’s easier to control the thickness of the coating and seems to wipe off more easily.

Lipstick was applied to the sides and underside of the chamber area to check for interference with the slide and frame bridge, respectively. The rear of the barrel feet will detect whether they’re contacting the front of the frame bridge. The lipstick on the barrel lugs was done to look for any unrelated weird contact with the slide lugs and didn’t show anything interesting, so that’s why you won’t see any further reference to the lug lipstick. (Side note: “The Lipstick Lugs” would be a great band name.)

Inserting the barrel into the slide, cycling it, and then disassembling revealed two things. First, it showed how having a tight bushing gets old really quick during the repeated assembly and disassembly involved with building a 1911. More importantly, it revealed the culprit behind the insufficient barrel clearance.

The bottom of the barrel was stopping on the frame bridge top before the lugs could contact the front of the bridge. This happened on my last build, leading me to suspect 1911 frame builders intentionally leave this area a bit oversized to permit adjustment for the barrel. This frame had some casting marks on the top of the bridge, so I predicted that by the time the marks were gone, the barrel feet would be stopping on the front of the bridge. To be fair, there was a bit of exploratory surgery going on: If the barrel feet didn’t go back far enough or the frame bridge didn’t go forward far enough, then lowering the bridge wouldn’t do anything and it would be time for some extremely unsavory tweaks involving the link. However, I wanted to clean up some of the casting marks anyway; if doing so started to show contact between the feet and bridge, then it would indicate I was on the right track.

Last time around I adjusted the frame bridge by wrapping a bit of sandpaper around a 1/2 inch socket, whose outer diameter of about 0.7 inches matches nearly exactly the radius of the frame bridge. It worked well then, and worked just fine now. (To be honest, it wasn’t until all the sanding was done that it occurred to me that I now had a lathe and could turn a rod of the exact diameter.)

In the above photo, you can see the some residual low spots as the top of the bridge is made even. I checked for barrel foot contact with the frame at several points in the process.

Almost there. The benefits of lipstick appear in the photo above, where it looks like there’s uneven contact. That’s actually because I built up the lipstick to detect incipient contact, and the layer I applied was a little uneven.

The sign that the barrel feet are about to contact the bridge comes when the fillet at the top of the feet starts to impinge on the forward edge of the bridge.

This isn’t mere contact, but two pieces of metal being jammed into each other. It happens because the lowering frame bridge changes the relief angle on the front of the bridge, so the solution is to file it back into proper proportion–but very carefully, lest too much of the bowtie get removed.

At this point, the finicky business of lowering the bridge became even more finicky due to dealing with two locations whose metal removal required coordination. It’s necessary to alternate between locations: File the bridge relief until there’s no more contact with the barrel, then check for foot contact. If it’s not there, lower the frame bridge until foot contact or, more likely, bridge relief contact results, then repeat.

To be extra safe, I started by not even changing the location of the bottom of the relief, but just angling the top farther back; there’s plenty of room on the top of the bridge, but considerably less on the bowtie.

There are no photos of this process because the amount of metal removed at each step isn’t readily visible. Instead of boring everyone with a series of nearly identical photos, I’ll just skip to the point where they become interesting.

The lipstick is not very visible at all against Dykem underneath because there is good solid contact that is squishing it flat. You can also see, on the left, where slightly uneven contact with the barrel feet has rubbed off some of the Dykem–pretty conclusive proof of contact.

You can see an impression of the bowtie on the feet of the barrel:

At this point, the barrel was linking down as low as it was going to go, but there were still scrape marks on the hood.

To clean up the last of the scrapes, I hit the rear of the hood with some sandpaper.

Note that the file in the above photo was not used; only 220 grit sandpaper, followed by 600 and 800 to remove sanding marks. Also, the lack of Dykem on the lugs shouldn’t be taken to mean I was sanding them–they just didn’t get coated completely.

That did the trick, reducing the scrape marks between barrel and hood from “dimensional interference” to “honest wear.”

In case you’re wondering why I went to so much trouble to eliminate scraping between the barrel hood and slide, there’s a good reason and a silly reason. The good reason is that it makes cycling smoother and eliminates a source of interference between two parts, reducing the number of factors at play during operation and potentially improving reliability. As a nice side effect, cycling is now smooth and slick.

The silly reason for working so hard on barrel hood clearance is because I want to blacken the stainless barrel to match the black trigger and make the entire gun look cool. Scrape marks would ruin the effect. And if you can’t indulge your aesthetic foibles when building a 1911, why bother?

Returning to the realm of functionally relevant dimensions, lowering the frame bridge moved the barrel ramp closer to the frame ramp:

There’s supposed to be about a 1/32 inch gap between barrel and frame ramps to provide clearance for the bullet ogive as it slides from the frame ramp to the top of the barrel ramp. If the gap is too narrow, it introduces a risk of the bullet nose striking the bottom of the barrel ramp and inducing premature link-up. The gap above looks a little bit tight to me, but I’m going to leave it as-is unless there are feeding issues, in accordance with time-honored engineering principle: “If it ain’t broke, don’t fix it.”

This chapter was longer than anticipated, which just goes to show that, where 1911s are concerned, even when everything works correctly, everything still takes work.

In fact, the barrel isn’t even completely fitted at this point. The remaining operation is headspacing the barrel, though; that can be broken into its own chapter–which is coming up next.


Chris has absolutely no qualifications to justify speaking with authority on any gun subject whatsoever. He compensates for being a poor shot by embarking on quixotic gunsmithing projects of both mediocre quality and dubious value. Because his taste in firearms runs to overpowered and outdated designs, Chris' opinions on guns should be treated with suspicion.

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