Question about 1911 barrel profiles?

[Rmiked]

Having bought a new DW Specialist (10mm) and disassembling it for cleaning, I am getting familiar with how the parts fit together. I noticed the barrel (match grade) has a larger diameter under the bushing (for lock-up) than the rest of barrel. So the barrel profile is NOT, uniform. That makes sense to me in that when the upper barrel lugs disengage from the slide recesses via the barrel link action, there must be enough clearance to allow the barrel to rotate down. I have seen barrels being sold from various manufactures (Wilson, etc) and in the photos I can’t see the step change in barrel diameter I am speaking of here. Do all 1911s have this step change in barrel diameter under the bushing like mine? Or is that a match grade barrel only? Maybe I can’t see the details in barrel pics I am looking at? Seems to me they all would need this diameter step change OR there needs to be enough slop in the bushing fit allow the barrel rotation down via the barrel link? And if some don’t have the tighter fitting barrel/bushing they would be inherently less accurate due to less precise fit? Thanks, just trying to learn how 1911s work.

[Robinson]

No not all 1911 barrels are a different diameter under the bushing, but some are. Also, bull barrels installed in bushing-less guns may be tapered on the muzzle end or may be thicker across their entire length. It depends.

However, a 1911 barrel will be thicker on the other end, which is the barrel hood and locking lugs. Many 1911 barrels have an abrupt step, others are tapered. For example, a Colt barrel marked N.M. seen on the production floor will have an abrupt step, whereas a match barrel also marked N.M. used by the Colt Custom shop typically has a taper. The stepped design is much more common.

[Rmiked]

Is it generally accepted that the barrels with larger diameter under bushing is a better design? I’m new to 1911s but before I got mine I wondered how the barrel could rotate down unless there was a diameter reduction at a point along the barrel where the tilting begins due to the link action? It seems to me the step change would accommodate that. I’m thinking the barrels without that diameter difference are just a looser fit?

I measured my barrel and bushing. The barrel step change is 0.006” smaller away from end along a length about the length of bushing. And the bushing inside diameter is 0.002” larger than the barrel end. So in lock-up, there is 0.001” clearance between barrel OD and bushing ID. The bushing ID has a step change also being smallest on the barrel end and larger toward the breech end of pistol. So there is additional clearance to allow barrel rotation (down due to link action) by the ID of bushing increasing (from end) and OD of barrel decreasing from end. So when the slide moves back there is additional clearance to allow barrel tilt designed into both the barrel and bushing. But very tight in battery with only 0.002” between bushing and barrel giving 0.001” on each side. I don’t think I ever understood this until now. I must say I am very impressed with the tolerances of this Dan Wesson pistol. It’s obvious some critical thought went into the design.

[Jim Watson]

Yes. Back when a GI barrel was all there was, it was usual to lathe turn the tube from bushing contact area back to the locking lugs, leaving a band for tight bushing fit.

There is also the ball bushing that rotates on a straight tube. First seen on the Pachmayr Signature System, more recently on the Briley bushing and some high end Smith and Wesson target models. I have a Briley, but they seem to be fading out in favor of "angle bore" bushings.

[YVK]

I noticed the barrel (match grade) has a larger diameter under the bushing (for lock-up) than the rest of barrel. So the barrel profile is NOT, uniform.

A long time ago I've read an advice of keeping a barrel half way out when turning the bushing. Supposedly that preserves a match grade fit. Dunno if true but, if anything, it makes turning the bushing easier.

[JAH 3rd]

I have a Springfield Loaded model and a DW A2, both in 45 acp. Both 5" barrels at the muzzle have a raised area under the barrel bushing. I'd say the raised area is somewhere between 1/4" to 3/8" in length. I bought the Springfield about 15 years ago, and the DW 2 years ago.