Machining of Rifling - Sterling 380

[Monac]

Does this barrel tell anyone about the way this gun was made (worn cutting tool, "chattering", etc), or does it just look like it needs to be cleaned? I saw it in an auction for a Sterling Arms Model 400 Mark II 380 automatic, and it just looked very odd to me. Maybe I am not used to seeing rifling under magnification.



This isn't a big deal, but all the little striations in the lands seem weird. Or have I been blind up to now, and all guns have those?

 

[5-SHOTS]

Yes, in my opinion it is absolutely chattering caused by the excessive forward speed of the (relatively long) tool that made the lands. In fact, it can be seen that in the last section of the barrel, when the forward speed had been decreased, chattering is practically absent. Subsequently the signs of chattering have almost totally disappeared where they used the tool that made the grooves.

 

[HisSoldier]

I had a small revolver that had rifling defects that looked much better than that, I sent it back to the manufacturer and it came back a couple of week later with a note from the house gunsmith saying it was OK. I finally sent it back and traded for a different model and the bore of that one was perfect.
The barrel in your photo looks terrible, the reamer must have been dull as heck and however they rifled it the bad reamer finish remained, and the marks continue through the lands and the grooves.

 

[5-SHOTS]

I think they used a tool like this, long and thin. The tool's excessive forward speed and its relatively low stiffness caused the chattering.

 

[BC17A]

That barrel was scrap before the broach cut the rifling. That bore finish is not a result of tool chatter, but from a worn tool when the bore was cut.

 

[PRD1]

The circumferential marks are from the reaming operation, prior to rifling, and exceedingly rough - a boring bar, as shown above, is not used for the purpose of reaming the bore. The manufacturer should have caught and rejected it, if they actually have a QC program. The depth of the striations is shown by the fact that rifling grooves (probably cut by broaching) are shallow enough (and the striations deep enough) that the rough surface was not completely removed by the rifling operation. It's a bad barrel, and the manufacturer should be willing to replace it.

PRD1 - mhb - MIke; barrel maker, retired

 

[edwardware]

Looks slightly worse than big-name rifle barrels made in the past 4 decades but not much. The blank is gun-drilled undersized, reamed to the minor diameter (leaving those swarf scars and some chatter), then it's rifled, in this case likely with a drawn cutter.

Most of the production Ruger, Remington, Winchester, and CZ rifles I own have similar bores, although deeper (?) hammer forge will iron out more of the scarring. In my experience you need to buy an aftermarket barrel, or firelap, to get a better bore.

 

[LiveLife]

Does this barrel tell anyone about the way this gun was made (worn cutting tool, "chattering", etc) ... auction for a Sterling Arms Model 400 Mark II 380 automatic

Wow, I would not be happy with that rifling and likely why the seller posted the picture of rifling.

Maybe I am not used to seeing rifling under magnification

Here are pictures of "humble" 22LR barrels and rifling (10/22 factory and KSA bull ... BTW 10/22 barrel is holding 1/2" groups at 50 yards even after 6500 rounds) - https://www.thehighroad.org/index.p...22lr-on-the-cheap.898035/page-2#post-12175261

And pistol barrels (M&P Shield 9mm, KKM, Lone Wolf) - https://www.thehighroad.org/index.p...g-oal-col-for-reference.848462/#post-11068318

 

[GooseGestapo]

I acquired a “Remlin” Model 1894 in .44mag, new production circa 2018. It was similar to the OP’s bore. With jacketed bullets, it was marginally shootable. Grouped 4-6” at 100yds. Cast bullets except for very light loads with 200gr RN (.44 spl), cast bullets were abysmal. Leaded badly too. Worst barrel I’d ever seen on a new gun.
The rest of the gun was beautiful! Nice well fitted wood. Smooth action, even fed semi wadcutters well.

Rather than spend money and time sending it back, I sold it to a Cowboy action shooter. He thought it shot splendid!
One mans trash is another’s treasure I suppose.

 

[Monac]

The circumferential marks are from the reaming operation, prior to rifling, and exceedingly rough - a boring bar, as shown above, is not used for the purpose of reaming the bore. The manufacturer should have caught and rejected it, if they actually have a QC program. The depth of the striations is shown by the fact that rifling grooves (probably cut by broaching) are shallow enough (and the striations deep enough) that the rough surface was not completely removed by the rifling operation. It's a bad barrel, and the manufacturer should be willing to replace it.

PRD1 - mhb - MIke; barrel maker, retired

The manufacturer, Sterling Arms of Gasport, New York (NOT Sterling Armaments Corporation of Dagenham in the UK) went out of business in 1984, as far as I can tell.

There is a story that Sterling was largely done in by a lawsuit resulting from a stupid teenager who found one of their double-action 380's in a house that his girlfriend was babysitting in. He thought it was empty after he pulled the loaded magazine out of it, and shot the kid the girl was babysitting in an effort to prove it (non-fatally, IIRC). The parents of the child sued Sterling on the basis that the gun should have had a magazine safety, and won. (I think it was in the late 1970's. That kind of thing happened then.) Sterling did not go broke then, but could no longer get liability insurance, or could only get it at a ruinous price. I also think that is why there is a "Mark II" 380; I bet it has a mag safety, although I don't know any of this for certain.

The company owner died in 2010. His obituary has a little more company history: http://gasportnewyork.blogspot.com/2010/12/sterling-arms-owner-has-passed-away.html

 

[Monac]

Many thanks to all of the good people who replied! I have learned a significant amount about barrel manufacturing and barrel quality from this, and that is just what I hoped to do by asking. Thanks again.

You know, cosmetically, this gun is actually pretty good. It looks like it has been shot very little, possibly for darn good reasons. It goes to show how it is the internal workmanship that can suffer first when a manufacturer is going under. Reminds me a little of the ill-fated Remington R51.

 

[5-SHOTS]

That barrel was scrap before the broach cut the rifling. That bore finish is not a result of tool chatter, but from a worn tool when the bore was cut.

The circumferential marks are from the reaming operation, prior to rifling, and exceedingly rough - a boring bar, as shown above, is not used for the purpose of reaming the bore. The manufacturer should have caught and rejected it, if they actually have a QC program. The depth of the striations is shown by the fact that rifling grooves (probably cut by broaching) are shallow enough (and the striations deep enough) that the rough surface was not completely removed by the rifling operation. It's a bad barrel, and the manufacturer should be willing to replace it.

PRD1 - mhb - MIke; barrel maker, retired

The bore (lands) of that barrel was not obtained with a drilling tool or a reamer. If it had been obtained with a drilling tool, even if the tool had been worn in some spots, the non-worn areas of the drilling tool would have erased those imperfections in the forward and return travel, since to extract the drilling tool from a part, the drilling tool or the part must remain in rotation. Same thing with a reamer. A worn drilling tool makes narrower holes not wider ones and doesn't produce marks deeper than the nominal diameter of the tool... Same thing with a reamer.

A cutting tool like the one I showed above was used to enlarge the internal of that barrel. Cutting tool which vibrated from the excessive forward speed and in fact vibrated a lot less when the operator suddenly decreased the forward speed of the tool near the exit of the muzzle (only one travel was made with that tool). The grooves were subsequently obtained with a broaching machine, probably one by one. This is probably one of the reasons why this pistols manufacturing company went bankrupt...

 

[lysanderxiii]

I think they used a tool like this, long and thin. The tool's excessive forward speed and its relatively low stiffness caused the chattering.
View attachment 1088014

No.

Barrels are drilled with tools like this:


Cutting fluid is pumped under pressure through the holes to force evacuation of the chips. And, the final pass with a gun drill will only go one direction, you do not withdraw them, but disconnect them and pass then through the work.



That barrel looks as if the cutter insert chipped about 1/4 inch into the final cut. It wasn't exactly super sharp to begin with, either. Also, you can tell that the rifling was button formed, as it just pushed over the poor surface finish of the boring. Cut or broached rifling would have cut out the bad sections.

 

[PRD1]

No.

Barrels are drilled with tools like this:

View attachment 1088151
Cutting fluid is pumped under pressure through the holes to force evacuation of the chips. And, the final pass with a gun drill will only go one direction, you do not withdraw them, but disconnect them and pass then through the work.

View attachment 1088152

That barrel looks as if the cutter insert chipped about 1/4 inch into the final cut. It wasn't exactly super sharp to begin with, either. Also, you can tell that the rifling was button formed, as it just pushed over the poor surface finish of the boring. Cut or broached rifling would have cut out the bad sections.

Your photos of deep hole drills ( the single-flute types) do show the type of cutting tool used to establish the bore through the solid barrel blank - it is pushed through the blank which is rotated at high speeds (the drill does not normally turn), and the chips are flushed out through the channel in the drill rod. The finish of a properly drilled hole is usually not as rough as shown in the OP, but is, in any case, considerably under the desired diameter of the finished bore. The final bore diameter is established by reaming, with one or more reamers which are pulled through the drilled bore of the blank, which is rotated at considerably lower speed than in drilling, and also with coolant flood through the reamer rod. Any tool marks remaining in the finished bore are those left in the final pass of the reamer (assuming the maker actually reamed the bore; which, in the OP, looks like the work of a dull twist drill). Those circumferential tool marks after reaming may be so insignificant as to need no further work to improve the surface finish, but can be improved before rifling by lapping, electro-polishing, etc.. Cut-rifling processes (single-point, broaching) will leave tool marks running lengthwise in the grooves, and, again, with properly designed, operated and maintained tooling, may require no further finishing operation after rifling, but can be improved by the same methods as bore finish. Rifling broaches are long, tapered cutting tools with ganged teeth of the desired rifling pattern, increasing in height and on the desired rifling pitch - they must be rotated mechanically as they are passed through the bore (though the same result can be achieved by rotating the blank), because it cannot rotate itself. Broaching may be accomplished with one or more broaches - rougher and finisher - for best finish and groove diameter control. Button rifling is produced by passing a very hard (usually a carbide) tapered 'button' with the desired shape, pitch and dimensions desired in the finished rifling - it can be made to smooth the remaining bore surface (the lands), also, and will lead itself through the barrel on the pitch established on the button, but can be 'helped' through the bore mechanically, to keep the final pitch as uniform as possible (button rifled barrels can have slightly inconsistent pitch due to variations in the hardness of the barrel material at different points in the blank). Hammer-forged barrels are made by passing a mandrel of the desired pitch and dimensions through a short, fat blank with an established bore, hammering the blank with great force to close the material around the mandrel while withdrawing and rotating the mandrel as the work progresses, producing a finished rifled bore and external dimensions of the blank - the chamber can also be established in the same operation. Hammer forged barrels will usually have the best interior finish, if the mandrel is properly made and maintained - the barrels pictured above are almost certainly hammer forged. The drawbacks to hammer forging are that the equipment is massive, very expensive, and the mandrels are not only expensive, but subject to breakage. There is another, fairly recent method of rifling: EDM, but that, too suffers from some drawbacks, in that the equipment is expensive, uses large amounts of electricity, and also requires a specifically-designed electrode for each rifling pattern and caliber to be made. EDM can produce very good barrels, but is not a widely used process ATT.
NOTE: No barrel making process or barrel maker I have knowledge of uses a boring bar for any step in producing a barrel blank.

PRD1 - mhb - MIke

 

[lee n. field]

Does this barrel tell anyone about the way this gun was made (worn cutting tool, "chattering", etc), or does it just look like it needs to be cleaned? I saw it in an auction for a Sterling Arms Model 400 Mark II 380 automatic, and it just looked very odd to me. Maybe I am not used to seeing rifling under magnification.

View attachment 1087991

This isn't a big deal, but all the little striations in the lands seem weird. Or have I been blind up to now, and all guns have those?

Looks like the bore of my Charter Bulldog.

 

[PWC]

Looks like it was the last barrel on the machine on Friday at 4;45, before the whistle blows.

 

[halfmoonclip]

With all due respect, why the interest in a Stirling? I've never seen one that actually works.
This has been a fascinating explanation of how barrels are rifled, and perhaps explains why hammer forged barrels seem to be increasingly the norm.
Thnx, guys.
Moon

 

[Monac]

With all due respect, why the interest in a Stirling? I've never seen one that actually works.
This has been a fascinating explanation of how barrels are rifled, and perhaps explains why hammer forged barrels seem to be increasingly the norm.
Thnx, guys.
Moon

I was interested in this gun because I had never seen a barrel that looked like that before, and I thought asking about it might teach me things about how barrels are machined (or forged, I guess, in the case of hammer-forged barrels). And as you kindly point out, it has been a great success in that regard.

I am aware of the reputation Sterling had before they went out of business. One of the first gun publications I ever bought was a magazine called "Handgun Tests" (like this on: https://www.amazon.com/Handgun-Tests-Magazine-Annual-1983/dp/B00B1GNFCW but an earlier year) whose writers were VERY outspoken about what they thought about the guns they tested. It did not last very long, and I cannot say I have ever seen anything quite so blunt in print form since. They did NOT like Sterlings, to put it mildly.

On the other, Sterling has been gone for almost 40 years now, so it may be time for collector interest to perk up, simply because they are old and most people have never seen one, especially the DA 380s. This may be the last time to get in on the ground floor!

BTW, if you think the Sterling DA 380's were bad, you should see their single action 380. It was sort of their first gun. (Sort of, because they had a slightly convoluted corporate history). That first 380 was made by taking a 22 target pistol that looked like a Khyber Pass copy of a High Standard Hammer B, shortening its barrel to about 1.25 inch, and reducing the grip length. Notice I did not say anything about increasing the slide mass, because they didn't. It was an ugly little wart best known for burning the hair off the knuckles of your shooting hand because of the very short barrel. Their later guns were actually a big step up.

PS - Here is a brief article with a photograph of the best looking Sterling SA 380 I have ever seem. Most of them looked rode hard and put away wet: https://www.all4shooters.com/en/sho...l-287-ppl-semi-automatic-in-380-ACP-features/

 

[5-SHOTS]

No.

Barrels are drilled with tools like this:

View attachment 1088151
Cutting fluid is pumped under pressure through the holes to force evacuation of the chips. And, the final pass with a gun drill will only go one direction, you do not withdraw them, but disconnect them and pass then through the work.

View attachment 1088152

That barrel looks as if the cutter insert chipped about 1/4 inch into the final cut. It wasn't exactly super sharp to begin with, either. Also, you can tell that the rifling was button formed, as it just pushed over the poor surface finish of the boring. Cut or broached rifling would have cut out the bad sections.

I'm not talking about how a barrel is made in general, I'm talking about how THAT barrel was made. And the bore of THAT barrel was done with a cutting tool for the reasons I detailed in my previous post. To understand this, it is enough to focus attention on the better finished section, near the muzzle: at that point the circular marks of the cutting tool become much denser and more regular because the operator suddenly decreased the cutting tool's forward speed just before it came out, while the rotation speed remained the same. In the less refined part you can only see circular signs of totally random depth and rather close together, a sign that the cutting tool was chattering like crazy. I am increasingly convinced that the cutting tool was one of those of the type without the insert which are thinner, to work inside a less than 9mm hole. Obviously, before using the cutting tool, the barrel had been drilled to a size close to that of the final bore. The cutting tool was supposed to provide the final fit and finish and in fact, if the operator had used the same forward speed he used near the muzzle, the finish would have been good all the way. I don't know why the operator worked like this. He was probably working with what he had available at the moment on a Friday afternoon. It is possible that THAT barrel is an exception and not the manufacturer's rule, but we have to discuss that, not how a barrel is normally rifled nowadays or back then.

Unlike a chattering cutting tool, a broach leaves regular and repetitive marks, sufficiently spaced, and signs of dragging and elastic return of the material. None of these signs are present in THAT barrel. And above all, a broach leaves the same marks and finish along the entire length of the inside of the barrel.

 

[PRD1]

While 5-SHOTS proposes and defends a possible explanation for the internal finish in the OP's barrel, I cannot agree with his conclusion, because the tooling and method he advocates is improper for the work. Final dimension and machined finish in firearms barrel bores has been produced by reaming for centuries, because a reamer, if properly designed, made, sharpened, maintained and operated will produce a very accurate and consistent diameter and surface finish - it is the accepted and universal method used by barrel makers. A boring bar, while useful when properly applied, cannot perform the same work as well, because the longer the bar (which must be substantially smaller in diameter than the work into which it must fit) the more it suffers from flex under loading, and must be adjusted for depth of cut, while a reamer cannot cut undersize, and does not usually cut much, if any, oversize, and while, in proper operation, leaves a very good surface finish. I cannot accept that any manufacturer of rifled barrels in series production would adopt or allow use of tooling and methodology not best adapted to the work. On the other hand, I have seen poor surface finish after reaming (though rarely as poor as in the OP) due to chipping of a flute or flutes of the reamer, which can then capture a chip or two, which it then drags through the bore, producing the scoring which is obvious in the OP. The chips are often harder than the barrel material, because the chips are work-hardened in the process (you may have seen drill chips which are turned blue by the heat produced, and are hard and brittle), and can produce the type of scoring seen in the example. As the use of a boring bar is both less efficient (and slower) than reaming, and subject to errors in operation which a reamer is not affected by, I think it improbable that a boring bar is responsible for the very poor surface finish in this barrel.

PRD1 - mhb - MIke

 

[halfmoonclip]

Monac, wouldn't count on investing in Sterlings as your retirement savings....
Now, that said, they should be uncommon cheap, if you want some just for grits and shins.
The link was amazing; have to say I never saw that model!
Be well,
Moon

 

[AlexS1]

This barrel was made by a spiral drill. I do not see final processing.
Lysanderxiii showed the right drill, I use such drills, but I can’t achieve perfect quality.
Here is a photo of the barrel I recently taken. After the lapping, they became smaller, but did not disappear at all. I hope you are interested in what I am writing.

 

[Monac]

This barrel was made by a spiral drill. I do not see final processing.
Lysanderxiii showed the right drill, I use such drills, but I can’t achieve perfect quality.
Here is a photo of the barrel I recently taken. After the lapping, they became smaller, but did not disappear at all. I hope you are interested in what I am writing.

View attachment 1088613

Thank you for posting! Learning about the various ways pistol barrels are made, or can be made, is why I started this thread, so yes, what you say is quite interesting. You actually make barrels yourself?!

 

[AlexS1]

You actually make barrels yourself?!

Yes )