Bending a barrel

[rrebuck]

A tightly fitting bullet will only go straight from a curved barrel, unless it is imparted with spin like a curve ball. Think of the type of sling that David used on Goliath. That projectile is spun and released, but doesn't curve, except for to gravity.

 

[Rawhide67]

I was skeptical about this process, but several months ago helped a friend bend the barrel (swamped octagon) on his old dgw 54cal. Prior to bending, you couldn't get it on target at 25 yards no matter how you adjusted the sites. I set up a crude way to measure the low point in the swamped area, got 2 blocks of wood on the cellar floor, set one under each end of the barrel, and my friend stepped on to the center of the barrel and bounced a few times. Did this a few times until I could measure a change, and then went to the range. Surprisingly, it worked.

 

[Flint62Smoothie]

Bending the barrel … also introduces internal stresses on the bullet that can lead to instability.

That is your speculation, but it is not backed up by material science and real world applications. Your statement of that German machine gun is correct, but you neglected to add that that was a FULL 90-degree turn to the barrel.

In fact, the truth is that EVERY modern ‘premium’ RIFLE (high velocity too, not just BP velocity) barrel maker straightens their barrels after machining. You tell me where those forces are any different than if one put a ‘slight’ bend in a fowler/musket or even a rifled BP barrel after receipt from the maker?

To date I’ve successfully have bent over half a dozen smoothie barrels, 3 for me and the rest for others. I have corrected the POI for 1 MZL rifle to date, but have also straightened 2 milsurp WW2 bolt action ‘bring back’ rifles where the muzzles were purposely bent to allegedly render them unshootable. Both were straightened to once again be ‘dead on’ @ 100-yards.

When I was doing barrel work, chambering, etc., specific to high end single-shot Schuetzen BP cartridge rifles, all barrels were checked and/or straightened (if needed) before and after fitting to the action. Was always best to have both the rear and front sight in as perfect inherent alignment as one could, before load development.

Just yesterday, I bent that barrel on that black powdah cartridge rifle I’ve referred to before in my posts. It only needed a ~0.030” deflection over a span of a 31” sight radius to bring the POI to the POA. Note one can’t see nor detect that change visually by the naked eye.

I tell ya’, opinions are one thing, but they become erroneous claims of ignorance in regards to barrel bending … especially when one has yet to bend even just ONE barrel …

 

[Johnny Tremain]

seen these when I was young

mounted

WARNING these are modern (black&white) pictures NOT muzzleloaders
It worked with 45ACP. This was my assigned firearm while in the Cav.

 

[Whiteoak15]

I built a barrel STRAIGHTENING jig that utilizes a dial indicator located at the midpoint between the barrel supports. You crank on the barrel a very little at a time and let it spring back. When you reach the yield point of the barrel, the dial indicator will not return to zero and you know the barrel has moved. You have to go very slow as a thousandth can make a notable difference.

 

[PathfinderNC]

I guess the proper term should indeed be “ barrel straightening” rather than “barrel bending” if the end result is a straight barrel rather than a bent one. This I can understand

 

[Pete G]

I guess the proper term should indeed be “ barrel straightening” rather than “barrel bending” if the end result is a straight barrel rather than a bent one. This I can understand

“Barrel regulation”

 

[Brokennock]

I was skeptical about this process, but several months ago helped a friend bend the barrel (swamped octagon) on his old dgw 54cal. Prior to bending, you couldn't get it on target at 25 yards no matter how you adjusted the sites. I set up a crude way to measure the low point in the swamped area, got 2 blocks of wood on the cellar floor, set one under each end of the barrel, and my friend stepped on to the center of the barrel and bounced a few times. Did this a few times until I could measure a change, and then went to the range. Surprisingly, it worked.

To date I’ve successfully have bent over half a dozen smoothie barrels, 3 for me and the rest for others. I have corrected the POI for 1 MZL rifle to date, but have also straightened 2 milsurp WW2 bolt action ‘bring back’ rifles where the muzzles were purposely bent to allegedly render them unshootable. Both were straightened to once again be ‘dead on’ @ 100-yards.

Just yesterday, I bent that barrel on that black powdah cartridge rifle I’ve referred to before in my posts. It only needed a ~0.030” deflection over a span of a 31” sight radius to bring the POI to the POA.

We're these "adjustments" made to correct elevation poi or left/right poi?

 

[Okie Hog]

One of the old time gunsmiths; think it was Hacker Martin, was quoted as stating that only one of the hundreds of barrels he forged did not require straightening.

 

[smo]

BN,

On my 16 gauge we moved the point of impact from 1” left and up 3-4” on a 6” Bull target at 25 yards.

I haven’t shot it much at 50 yards, but I did hit a full size target target at 40 yards with a patched ball.

It’s nice too finally be able too aim where you want the shot or ball too hit.

 

[Dutch7]

One of the old time gunsmiths; think it was Hacker Martin, was quoted as stating that only one of the hundreds of barrels he forged did not require straightening.

“Bend it straight” is the phrase I recall hearing. One barrel I have 7/8x42 octagon was shooting low right several inches at 25 yds (4o’clock) I tweaked it (straighten it) on my bench with a vise and a bit of pressure in the opposite direction (10 o’clock) only took once to bring it back in line.
Another barrel has a bore run out problem and it is minor and corrected with sight position. I have lived with it for 35 years so I think I can manage a while longer

 

[PathfinderNC]

I think bore run-out would be a major issue. Barrel-straightening apparently not

 

[dave951]

That is your speculation, but it is not backed up by material science and real world applications. Your statement of that German machine gun is correct, but you neglected to add that that was a FULL 90-degree turn to the barrel.

In fact, the truth is that EVERY modern ‘premium’ RIFLE (high velocity too, not just BP velocity) barrel maker straightens their barrels after machining. You tell me where those forces are any different than if one put a ‘slight’ bend in a fowler/musket or even a rifled BP barrel after receipt from the maker?

To date I’ve successfully have bent over half a dozen smoothie barrels, 3 for me and the rest for others. I have corrected the POI for 1 MZL rifle to date, but have also straightened 2 milsurp WW2 bolt action ‘bring back’ rifles where the muzzles were purposely bent to allegedly render them unshootable. Both were straightened to once again be ‘dead on’ @ 100-yards.

When I was doing barrel work, chambering, etc., specific to high end single-shot Schuetzen BP cartridge rifles, all barrels were checked and/or straightened (if needed) before and after fitting to the action. Was always best to have both the rear and front sight in as perfect inherent alignment as one could, before load development.

Just yesterday, I bent that barrel on that black powdah cartridge rifle I’ve referred to before in my posts. It only needed a ~0.030” deflection over a span of a 31” sight radius to bring the POI to the POA. Note one can’t see nor detect that change visually by the naked eye.

I tell ya’, opinions are one thing, but they become erroneous claims of ignorance in regards to barrel bending … especially when one has yet to bend even just ONE barrel …

If you think that it's just my opinion, then please explain why the Krummlauf, the Stg44 barrel attachment that allowed shooting "around corners" had such a short lifespan in use, like about 300 round max for the 30deg variant and pitiful accuracy. There were TWO versions of this attachment- 30deg and 45deg. The barrel life for the 45deg was even shorter, like 100 rounds. In BOTH variants, the bend in the barrel caused the bullet to fragment upon exiting the muzzle. THIS IS NOT MY OPINION, IT IS VERIFIED BY EXPERIMENTATION BY THE ALLIES POST WW2.

Now, at no point have I EVER dismissed barrel bending as a cure for problems caused by internal stresses induced by the rifling process. Those stresses are a well documented fact BUT, not every barrel has these problems. Again, observation and experimentation will reveal if a barrel can benefit from tweaking. I would exhaust all other possibilities before tweaking a barrel.

Before getting on yer high horse, remember that reading and thinking is fundamental. And how in the world would you KNOW IF I'VE NEVER BENT A BARREL??

 

[LME]

I can see where people get confused? When one says bending a barrel you would think they meant to a already straight one? I have never straigtened a barrel. In the shop many drive shafts were straightened and other things that were bent. My father straightened a 1887 Winchester lever shotgun barrel that was visibly crooked.It patterned fine afterwards. I didn't stay in the shop I decided to do contract work. I have regrets some times.

 

[Col. Batguano]

In order to curve, the bullet needs external forces exerted on it, and it will yield to those forces if they are greater than any resisting force.

Think about a thrown baseball. Your arm inthroning the ball in a rather tight arc, but the ball goes straight after you release it. If there is any lateral curve to it, it's because any spin put on it increased the air pressure on one side and / or decreased it on the other. Hook and slice golf balls are the same way.

A related question might be; why do the balls have to travel a certain distance before it appears that they start curving? The answer is; they are curving at the same rate for the entire distance, but the sudden APPEARANCE of a "snap hook" is just the cumulative effect of the continuous "piling on" from all the prior movement. They appear to curve faster because they've slowed down a whole bunch from the velocity they started out with, and the pressure differential is greater percentage wise as the ball is approaching the plate. Since the spin rate is essentially the same, the differential in pressures is much greater percentage wise.

Or, to use a hypothetical; a major league curve ball spinning at 2500 rpm creates a 2 psi pressure differential from one side of the ball to the other. As the ball leaves the pitcher's hand at 85 mph there is 30 pounds of resistance. The 2 psi differential is a 6.66% difference. As the ball slows down to 76 mph as it approaches the plate the differential increases to 7 1/2%, and the ball increases the rate of the curve as well as the curve per distance covered, which makes it curve faster (relatively speaking), and that much harder to hit.