Are double rifles really that tough to make?

[tommer]

It seems that whenever the subject of double rifles comes up, someone asks why they aren't common and then someone else points out that they're tough, i.e. difficult to make.

The problem, apparently, is that it's a laborious process to "synchronize" the barrels in order to make a real shooter.

Is this still the case, or is this some leftover knowledge from the bad old days? It wasn't too long ago that Remington was listing imported Baikal doubles for around $400. They have sinced disappeared from the line up.

 

[ArmedBear]

Apparently they couldn't make them for 400 bucks.

 

[rantingredneck]

Either that or they weren't worth the 400 bucks due to lack of good synching of the barrels.

 

[JesseL]

It seems to me that it wouldn't be all that tough to make them these days, with a little judicious application of technology.

To oversimplify it:
Put a laser bore sighter in each barrel, mount them both in a jig, regulate them to the same POA, and CNC weld them together. Voila, a cheap and easy double gun, with reasonably good regulation.

 

[JohnBT]

I saw a series on regulating double rifles. Shoot. Take the barrels apart and adjust and resolder them and put it all back together. Go shoot. Take the barrels apart, etc.

From an NRA magazine article:

"One of the big expenses of building double rifles is the time consuming and highly skilled practice of regulating the barrels by firing and adjusting with shims and solder to get both barrels hitting the same point on the target with the one set of sights. "

 

[Vern Humphrey]

If it could be done that easily, it would be done. And you could buy double rifles for what low-grade double shotguns cost.

But it can't be done -- even in bolt action rifles, each rifle is a law unto itself and must be zeroed individually.

 

[ceetee]

Put a laser bore sighter in each barrel, mount them both in a jig, regulate them to the same POA, and CNC weld them together. Voila, a cheap and easy double gun, with reasonably good regulation.

The biggest market for doubles has always been in the dangerous-game arena. You get two quick shots in whatever really heavy caliber you fancy. Alternatives are bolties that aren't as quick with follow-up shots, or auto-loaders that can't handle the big-bore loads. A guy that can afford guided dangerous-game hunts, can also afford to have a really, really good double rifle. Now, if you were facing down an African lion, would you want your rifle's regulation to be "reasonably good"?

 

[ArmedBear]

Put a laser bore sighter in each barrel, mount them both in a jig, regulate them to the same POA, and CNC weld them together. Voila, a cheap and easy double gun, with reasonably good regulation.

That might work with a shotgun, where the shot doesn't rotate. A well-made barrel should shoot to a relatively predictable point.

But a rifle involves vibrations and harmonics which vary radically when you attach two barrels together. The twisting bullet in the barrel makes things really interesting; Newton's Third Law ensures that the barrel will also go through some twisting contortions when it's fired. You can't twist the bullet without having an effect on the barrel.

Take a clothesline, shake it until you have a nice standing wave pattern in it. Now have someone hang a shirt on it. The wave patterns will be utterly unlike they were before.

That's why people free-float barrels, or bed barrels: to avoid any such variation in the vibration of the barrel. In the case of free-float barrels, you want to isolate the barrel vibration from a sling, bipod, hand position, etc., as well.

Now a double rifle is the exact opposite of a free-float. But you can't just adjust the sight like you would with a regular rifle. The two barrels have to shoot to the same spot, so you have to move the barrels. However, the solder, etc., changes the POI, so when you set up the barrels, you can never say exactly WHERE they'll hit until you cool them off and try it.

 

[JesseL]

But it can't be done

That sounds like a challenge if I ever heard one.

Perhaps the final regulation cold be done by machining a precise angle offset to the crown of each barrel?

I think it could be done, but the market for double rifles is tiny and nobody really wants to invest in the R&D and equipment to develop a suitable process. Especially since so much of the desirability/romance of the double rifle is tied up in the nature of their craftsmanship.

 

[ArmedBear]

Jesse, read my post above for why a bit of R&D is not what it takes.

Precise and dead-on mathematical modeling of barrel harmonics is what it would take. I don't believe we can do that yet. Descriptive modeling, perhaps, but not predictive modeling.

Complexity theory makes some things a real bitch. That's why they originally called it Chaos Theory, with is probably still a more viscerally satisfying term for it.

Bottom line? Bore sighting is usually enough to get you on paper. But then you still have to sight in a gun, and nobody can predict exactly where the POI will be.

 

[JesseL]

I understand the difficulties.

But if people can reliably make accurately regulated barrels by the solder-test fire-unsolder-shim-repeat method, it should be just as possible to adjust the point of impact of each barrel without depending on such a laborious process.

 

[PercyShelley]

Easy: make a double rifle where the barrels aren't soldered together!

 

[ArmedBear]

Did you read my post, though?

The solder and shims themselves change the POI. If there were a way to make both barrels free-floated, then you'd be right. But as long as they're attached, the attachment screws your plan.

(Percy beat me to it)

 

[Vern Humphrey]

Easy: make a double rifle where the barrels aren't soldered together!

The Russians make just such a rifle, with a screw arrangement holding the muzzles together. You regulate the rifle by turning the screw. The problems are:

1. It's butt-ugly.

2. It's an over-and-under, not a side-by-side (and most people want side-by-sides in a double rifle.)

3. It's only chambered in smaller cartridges (like the .30-06) and not the grand old double rifle cartridges.

 

[JesseL]

Did you read my post, though?

Yes, I did.

I realize that with any method of adjustment there are going to be undesired second order, third order, etc. effects and a certain degree of trial and error is necessary. But if trial and error shimming works, why not another method that will at least not require so much labor?

 

[tommer]

I've seen a few Valmet 412s on Gun Broker for about $1,000. They're used of course, since Valmet went out of business or got bought up, but they probably didn't sell for much more than that new.

Thing is, they're O/U, not SxS. Is an O/U double easier to synch than a SxS?

 

[ArmedBear]

The problem I can see is that any method of securing the adjustment, once made, will change the POI. So will any method of holding the barrels in place while testing them.

It's all about mastering the math, and we haven't.

 

[Vern Humphrey]

I realize that with any method of adjustment there are going to be undesired second order, third order, etc. effects and a certain degree of trial and error is necessary. But if trial and error shimming works, why not another method that will at least not require so much labor?

Because there isn't any such method.

Consider the suggestion of using a laser to align the barrels. While that sounds high-tech, you can do the same thing by simply opening the breech and looking through the barrels -- which is exactly what the old-time gunmakers did. And then they shimmed, soldered, shot, unsoldered, re-shimmed, re-soldered, and so on.

 

[ArmedBear]

You could make a two-barrel rifle pretty easily. Have completely free-floated barrels like an AR can have, with adjustments where the barrels are attached.

But that wouldn't be a double rifle, in the way we mean it here, as in a finely-balanced, light, quick, eminently pointable fine firearm.

 

[JesseL]

The problem I can see is that any method of securing the adjustment, once made, will change the POI. So will any method of holding the barrels in place while testing them.

Hence my suggestion of regulation via offset angle crown cutting. Do it with the barrels already permanently attached and you'll minimize interference from other changes, unlike soldering, shimming, resoldering, and hoping you don't screw it up again when you finally solder in the rib.

You don't have to be able to calculate exactly what angle is going to be necessary to achieve perfect regulation on the first try, you just have to be able to get reasonably repeatable results from a given adjustment, which must be possible since they already do it.

Because there isn't any such method.

Well duh. There won't be until someone develops one.

 

[Ash]

The Valmet doubles can still be had made by Marocchi called the Finn Classic.

Ash

 

[ArmedBear]

Don't you have to get pretty darn close to use offset crowns to sync the barrels?

How far can you tweak the POI that way?

 

[Jim Watson]

The lighter caliber Krieghoffs, the cheapo vaporware Baikal EAA - Remingtons, and the O/U Tikkas have jackscrews for some degree of user adjustment of regulation.

I saw a picture on Nitroexpress.com of the shim packets used to adjust regulation conventionally. They are folded sheetmetal, adjusted by unfolding and clipping off the excess. Folded beercan was recommended for the DIY shotgun to rifle conversion. Looks pretty rough until it is assembled and covered by the top and bottom ribs.


I also once saw an article on frontier firearms. There were several double shotguns with the muzzles filed at an angle in an effort to regulate with punkin balls.

 

[Funderb]

Why?
A semi auto is just as good and better.
There really isn't much point to it.

 

[ArmedBear]

A semi auto is just as good and better.

Sure. Lots of quick, light, well-balanced semiautos in Express calibers are readily available.