Flexing a barrel

[M. De Land]

I have bent one barrel in my milling machine between V blocks using the quill screw for the pressure lever to get it to shoot point of aim for a friend and he was happy with it but I would be surprised if it would stay put after 3- 4 shots.
The trouble with crown manipulation or barrel bending on anything but vertical alignment is you only have one convergence point at a given distance with the sight registry. It's like a fighter aircraft with wing mounted guns instead of nose mounted guns. Once the line of fire crosses the convergence point with sight registry the ball/bullet keeps right on going off convergence on a tangent. If orientated on the vertical than trajectory helps correct the cross axis registry. Same deal on a double gun with one set of centered sights which are actually barrel bent with wedges to one point of aim at a given distance.
The reason a filed crown is not a good idea is because when the bullet or ball leaves the muzzle the gas escapes one side faster than the other and creates a "retro fire" type correction, with a conical this sets up an off axis bullet release that imparts nose oscillation or wobble in a rifle which may or may not self correct. A ball would be more forgiving most likely but it should be remembered that a shot ball is not a true sphere any longer but more of a double, spherical ended,cylinder .

 

[Erwan]

I bent two 1777 rifle barrels like in the old days: wooden wedges and a big, heavy mallet also made of wood.
I also straightened a barrel of one of my Tryon which had a nice ring (I forgot that the bullet was pushed just with the short starter and not with the ramrod ) and this barrel have been cut by four inches, but it was shooting too high, but now it is superbly accurate and shoot right, I did it with my big mallet too...
This was the traditional method used in Tulles, Saint Etienne etc, but it is now forbidden in competition, especially for anything MLAIC, for other organizations I don't know...

 

[Britsmoothy]

with a conical this sets up an off axis bullet release that imparts nose oscillation or wobble in a rifle which may or may not self correct.

Is that an hypothetical assumption or have you test data?

 

[M. De Land]

Is that an hypothetical assumption or have you test data?

I have not tested this personally but read of it and saw a diagram of the effect, I think in gunsmith school many years ago. I believed it as it made sense to me from a physics perspective. We know for a fact that bullets in flight have nose yaw even if perfectly released from a bore muzzle that will either self correct or deteriorate to over turn at some point in some cases.
Also it is true that good crown geometry can be made by hand with the proper tooling but usually is easier and more accurate accomplished in a lathe.

 

[Okie Hog]

Read an interview with an old time gunsmith who made barrels from flat iron. maybe it was Hacker Martin. He knew of one barrel that did not require bending.

 

[Britsmoothy]

I have not tested this personally but read of it and saw a diagram of the effect, I think in gunsmith school many years ago. I believed it as it made sense to me from a physics perspective. We know for a fact that bullets in flight have nose yaw even if perfectly released from a bore muzzle that will either self correct or deteriorate to over turn at some point in some cases.
Also it is true that good crown geometry can be made by hand with the proper tooling but usually is easier and more accurate accomplished in a lathe.

It is easy for our generation/s to view this from the perspective of analogue and cnc machinery.
But please for a moment try to think how it was achieved in 1727ad!

There are videos available showing how rifle barrels can be cut and crowned by hand. Some videos show before and after effects. Some show a zero change. No doubt via the very subtle change from an assumed true square muzzle but alas still a functioning and accurate rifle.

A general line of thought not directed to any one.....

One thing I was always taught. Assume nothing and don't trust experts. Experts tend to hamstring an open mind and assume is made up of words like *** and me with a tiny u in the middle!

 

[Brokennock]

I have bent one barrel in my milling machine between V blocks using the quill screw for the pressure lever to get it to shoot point of aim for a friend and he was happy with it but I would be surprised if it would stay put after 3- 4 shots.
The trouble with crown manipulation or barrel bending on anything but vertical alignment is you only have one convergence point at a given distance with the sight registry. It's like a fighter aircraft with wing mounted guns instead of nose mounted guns. Once the line of fire crosses the convergence point with sight registry the ball/bullet keeps right on going off convergence on a tangent. If orientated on the vertical than trajectory helps correct the cross axis registry. Same deal on a double gun with one set of centered sights which are actually barrel bent with wedges to one point of aim at a given distance.
The reason a filed crown is not a good idea is because when the bullet or ball leaves the muzzle the gas escapes one side faster than the other and creates a "retro fire" type correction, with a conical this sets up an off axis bullet release that imparts nose oscillation or wobble in a rifle which may or may not self correct. A ball would be more forgiving most likely but it should be remembered that a shot ball is not a true sphere any longer but more of a double, spherical ended,cylinder .

You're convergence issue for vertical changes is a non-starter.
A ball, or bullet, rises above the line of sight and drops below it again anyway. This is why (as much as I still don't like the idea) if a barrel is to be bent, bending for elevation correction is possible. Windage correction results in the problem I noted earlier in that it will only be "on" at one distance.

The reason a filed crown is not a good idea is because when the bullet or ball leaves the muzzle the gas escapes one side faster than the other

And yet, this has been done traditionally, and, that difference in gas speed is why it works.

 

[M. De Land]

Not denying crown manipulation can deflect a projectiles path but it's not the best idea for it's stability in flight, particularly with conicals.
The reason all barrels should be run out orientated to trajectory (vertical) and not windage (horizontal) is so that there is only one plane variability (trajectory) given a calm air, sight zero (windage). With a calm air sight setting windage is not going to continualy change in relation to the sights as happens with trajectory. One mans opinion .

 

[smo]

Thanks for the explanation Brits..

So if I were hitting let’s says at the 7 o’clock position on the outer ring of a 6” bullseye target when aiming dead center.

I would need too file in the 7 to 1 o’clock direction or 1 to 7 as long as the crescent is at the bottom 7 o’clock position… This would move the impact up and to the right correct?

I’m talking about shooting a patched ball out of a smoothbore with only a front non movable sight.. not necessarily an octagon barrel…
Those I’ve always managed too correct by sight adjustment alone.

 

[Cvkotvkse]

Over the years, I have read accounts of everyone from my Native ancestors to the late Hershel House using this method... To me, it seems like an effective method to improve things, but not the best one... and probably more effective, with fewer problems, when the issue is a vertical bend (we use gravity to accomplish the same thing with our blowguns...point the bent end up, and it "droops" into a straight line... )

 

[M. De Land]

Over the years, I have read accounts of everyone from my Native ancestors to the late Hershel House using this method... To me, it seems like an effective method to improve things, but not the best one... and probably more effective, with fewer problems, when the issue is a vertical bend (we use gravity to accomplish the same thing with our blowguns...point the bent end up, and it "droops" into a straight line... )
[/QUOTEj Presactly !

 

[M. De Land]

Over the years, I have read accounts of everyone from my Native ancestors to the late Hershel House using this method... To me, it seems like an effective method to improve things, but not the best one... and probably more effective, with fewer problems, when the issue is a vertical bend (we use gravity to accomplish the same thing with our blowguns...point the bent end up, and it "droops" into a straight line... )

Another factor that should be considered in my opinion is the material modern barrels are made of . In history the barrels were made from flat iron strips or scalps and were forged into a tube and seam forge welded their length. The iron was soft and much more malleable than is modern alloy steel barrels. The only way to get them straight was to bend them that way. Soft iron barrels do not hold stress like the much harder and tougher modern steel barrels do so what was a valid traditional fix is not the best technique with modern barrel material .
When cast steel became the industry standard and barrels were rolled out over a bore mandrel with no seem to deal with bores became aligned better and less straightening was required. Another factor is when cartridges became standard then barrel lengths shortened considerably so the shorter barrel lengths required less alignment to make them acceptably accurate for common use.

 

[Britsmoothy]

Thanks for the explanation Brits..

So if I were hitting let’s says at the 7 o’clock position on the outer ring of a 6” bullseye target when aiming dead center.

I would need too file in the 7 to 1 o’clock direction or 1 to 7 as long as the crescent is at the bottom 7 o’clock position… This would move the impact up and to the right correct?

I’m talking about shooting a patched ball out of a smoothbore with only a front non movable sight.. not necessarily an octagon barrel…
Those I’ve always managed too correct by sight adjustment alone.

So looking down the barrel from the breech you would remove a tiny amount from the 7 o'clock position. To do that you have to look at the muzzle. So now the area to remove a tiny amount is 5 o'clock.
Put another way. The opposite side from the cresent or tiny relieving, bevelling or filing is the direction the the shot or ball will go.
Remember, just a tiny amount and try to note how much then test.

 

[Britsmoothy]

Mentioning assuming again.
Most assume the only accurate way to crown a barrel is by accurate machines.

Well my cz 457 17hmr crown viewed in a magnifying glass would have most cringing .
The bevelled crown is in fact not even. That means gas is venting earlier on one side!
Still shoots tiny groups! So much for cnc machinery!
Another rifle I had decades ago (222) had had its barrel parted off so fiercely it had in effect crimped the last 1/8" . It was a bear to get a load for. Right up to the point I noticed via a magnifying glass, cut it off by hand, refinished the muzzle and crown by hand and then it finally shot good groups and was less load fussy! So much for machinery!

Some outfits have all the gear but have no idea how to use it!
Some have no gear but know what is needed!

 

[Eterry]

My friend the professional gunsmith said he's bent over 100 barrels. He actually built a jig to hold them and a dial micrometer to see how much he's moved it.
He has a letter from Harry Pope advising how he bends a barrel from the 1950's. They all bent them, and still do.

 

[45man]

My friend had a bent TC barrel and I used wood blocks and a big "C" clamp to fix it on my bench top. It worked perfectly.

 

[helwan9]

I have used the barrel bending method to fix ml Revolvers to fire to point of aim for years. Worked for me!

George

 

[smo]

Brits , Thanks for the explanation

 

[ZUG]

You're convergence issue for vertical changes is a non-starter.
A ball, or bullet, rises above the line of sight and drops below it again anyway. This is why (as much as I still don't like the idea) if a barrel is to be bent, bending for elevation correction is possible. Windage correction results in the problem I noted earlier in that it will only be "on" at one distance.


And yet, this has been done traditionally, and, that difference in gas speed is why it works.

Brokennock I have an issue with your statement "A ball, or bullet, rises above the line of sight and drops below it again anyway" as not being totally correct. The projectile does not RISE when it leaves the barrel's bore but leaves the barrel's bore in a straight line to the target and gravity eventually guides the projectile to earth as the velocity decreases to zero. The sight is angled up to allow for the projectile to travel in an arc so that it will impact the target at a prescribed distance. Here is an excerpt from another on this same subject:
Understanding Bullet Trajectory

Bullet trajectory has a different flight path than what the shooter sees in their line of sight. Optics and iron sights are mounted above the barrel and there is an offset of about 2 inches on average. The straight line the shooter see in their line of sight, the bullet is going to have a line of departure which is straight out of the muzzle. The muzzle is always aimed upwards making the bullet travel in an arc.

At some point, the bullet trajectory and the shooters line of sight have to intersect which is at the zero. Since the bullet is at an upward flight path, the shooting position to the shooters zero, the bullet will continue upward and then fall down. The shooter max ordinate is the highest point that the bullet trajectory will go until gravity takes over and the bullet starts to drop.

 

[M. De Land]

So looking down the barrel from the breech you would remove a tiny amount from the 7 o'clock position. To do that you have to look at the muzzle. So now the area to remove a tiny amount is 5 o'clock.
Put another way. The opposite side from the cresent or tiny relieving, bevelling or filing is the direction the the shot or ball will go.
Remember, just a tiny amount and try to note how much then test.

Precision barrel straightening (if it exists) is done in an over head barrel vice looking through the bore at a vertical string or wire. The barrel is rotated and any break in the shadow line showing down bore from the wire is a bend in the barrel . The vice pressure is applied by the wheel until all the shadow lines are unbroken around the clock. The out side straightness is only a rough reference to how straight the bore actually is.