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Discussion Starter #1
Gentlemen,

I'm in need of advice/opinion of a most technical nature. Last month I managed to locate a .380 barrel and complete upper for my Astra 3000. This is like finding a needle in a haystack because Astra 3000's are very uncommon, in fact; mine is the only one I've seen this side of the Atlantic. The complete upper is in good condition, but the barrel came with a good sized bulge in it. I'm currently seeking out ways to reduce the size of the bulge and see how she shoots. I've shot several pistols and revolvers with bulged barrels, and 9 out of 10 times, accuracy isn't affected enough that I would bother changing barrels. So the thought is, if I can repair the barrel enough to shoot it, it would probably be fine. But if it doesn't, that takes me to plan B.

Plan B
The Astra 3000 barrel is a very simple design, and I was thinking about just making one. Long years ago, I made a few barrels for Browning 1910's and the Astra 300/3000 barrel is nearly identical to the Browning 1910. So my little pea brain says, if you're going to make a barrel, why not make it extended a bit and thread it for a suppressor?

Here's the dilemma, and where I need some opinions from those with a wider range of experience. The Astra's barrel isn't fixed in the frame like a PPK, it sits in the frame wedged in-between the frame and slide at the rear, and the barrel bushing up front; very much like a Browning 1910. My worry is by adding some significant weight on the end of the barrel, would that cause the barrel to bind in the slide? Or will the barrel bushing give it enough support to keep it from binding?

Now I tend to fall into the "it would work just fine" camp, but I'm soliciting opinions just in case someone comes up with something I haven't thought of yet.
 

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You're ahead of me... I've only seen pictures.

Like you I've shot bulged barrels with no concern but assuming that the bulge interferes with the slide travel and needs a fix I've always wondered if something I've heard about for shotgun bulges might work. I haven't done it, but my understanding is that there is a roller tool that can swage the barrel back down. That might not be too hard to make.

Plan B has a certain appeal though... hanging weight on the barrel is going to make the bushing become the fulcrum or pivot point. Light weight can... lots of grease :?:
 

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Discussion Starter #3
Yep, that’s my thinking. I know somewhere in my travels, I’ve seen a roller setup. But your mentioning of a shotgun barrel brings me to another possible solution.

There are a lot of people who fix a shotgun barrel dent with a hydraulic device that presses the barrel back out and although this works, there’s a much better and less invasive way to do it. You use plug gauges and lightly press the gauge as you tap on the barrel with a small hammer. Basically, you’re forging the barrel back into place. If you have a good set of plug gauges (and I don’t anymore, but I know someone who does), you can make a shotgun barrel look new and not even mess up the finish.

Now a .380 barrel is much thicker than a shotgun barrel, but I think the same idea could work. The idea is to get the outside diameter of the barrel back down to a size that allows the gun to function freely. But you don’t want to make the rifling touch the bullet again because doing so could negatively affect accuracy. Hmmm…Need to call a friend. Thanks Charlie, you have stimulated some brain cells.

I may still try plan B just because I haven’t made a barrel in decades.
 

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You could always just turn the OD down to where it needs to be. Cold blue ain't all bad.

I'm familiar with the swaging tools for shotgun barrels but never thought of the plug gauges... do have a set of those but, sadly, no bulged shotguns.

The tool I am thinking about looks just like a knurling tool except smooth. Just goes in the lathe tool holder. Don't know if a mandrel is required or not.

You might also want to call Brownells. They have some pretty smart folks.
 

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Discussion Starter #5
Yep, you and I are thinking of exactly the same tool, I'm trying to find someone with that tool.

As for turning it down, I'm a bit wary of that because it will drastically thin the wall of the barrel. Not that a .380 is a high pressure round, but I'm just on the careful side.
 

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I can't blame you for caution, but turning may be the best answer. Obviously you can figure out how much it would be thinned and the location of the bulge is important.

IMX bulges are usually at least half way down the barrel. Since Pmax is probably before the bullet is even out of the case and certainly before it travels an inch it should be fine unless you reduce the wall thickness by more than 50%/

Actually I think I can give you a good estimate of pressure from Quickload if you give me the barrel length, location of the bulge and wall thickess.
 

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The lathe setup Charlie mentions could be done without a mandrel, but prudence suggests that one be used. I've never tried what you suggest and am not sure of the pressures required, but believe they'd be substantial.

The one setup I've seen (Brownells Kinks?) showed opposing V blocks and a hydraulic press to reduce the bulge.
 

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I saw a barrel get de-bulged where the smith chucked it in the lathe and while it spun, he used a smooth blunt piece of cutter tool to slowly just swage it back down. Be careful, you can swage and thin the barrel at the same time. also you could create a tight spot.
 

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There must be some bad vibes going around because one of the pretty good shooters at my range bulged a Kart .45 barrel Sunday. He gave it to a friend who has some exceptional gun skills. I think he's going to turn it down and I'll help him fit it if needed.
 

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Remember folks, we are talking Spanish metallurgy from the 1930s...

I would be very nervous about trying to recover a damaged gun barrel.

Geoff
Who remembers a motorcycle shop in the 1960s trying to work on Bultacos.
 

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I'm sure it's pretty technical maybe along the same esoteric knowledge as EDM machining, but what about using an electromagnetic ring, with a mandrel inside just in case?

I saw that Canuckian "How it's Made" or whatever show a few months ago, and saw then how the open "can" ends of some automotive fuel pumps are rather cleanly crimped around the plastic innards. Always wondered how they got it so smooth with no marks on the cadmium finish.

On the other hand, that metal is only maybe .05" thick, but it's probably the same hardness (or lack) as an old Astra barrel.

The force on the metal decreases by the inverse square law, you know. If I got it right. I'm sure it was magnetic repulsing based on some polarity being built in. The electromagnet was outside and the metal just squeezed in without anything touching it. Looked downright spooky.

Just thinking...as requested.
 

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EDM is a piece of cake because it is really just a controlled spark and ECM (electro chemical machining) can rifle a barrel like cutting butter but those remove metal.

I know a magnet can be used to pull a dimple out of sheet metal but to iron out a bulge but how much magnetic power would it take to move steel that is 0.10" thick on a side. Then you would need to make one pole of the magnet exactly the same size as the bulge to suck it back in.

I suppose the theory is there... :?
 

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Discussion Starter #18
Skeptic49 said:
Remember folks, we are talking Spanish metallurgy from the 1930s...

I would be very nervous about trying to recover a damaged gun barrel.

Geoff
Who remembers a motorcycle shop in the 1960s trying to work on Bultacos.
It's from the late 1940's and I've never known Astra to make anything but a top notch pistol
 

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Discussion Starter #19
FYI,

I turned the barrel down this weekend and had a successful test fire using the original slide and magazine; works perfectly. The crown was badly damaged when someone obviously tried to pound the gun open after the barrel bulged. Accuracy wasn't very good, but I have yet to really deal with the crown isssue, but she works.
 
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