barrel flex

[hammer111]

I apologize for making you have w copy a paste the link, but it's worth watching. Never mind it did work.

Blew my mind at the amount of flex in a gun barrel.

[ame]http://m.youtube.com/watch?v=AqgPu9gSmVc[/ame]

 

[J E Custom]

Check this out. These test show how much a barrel can flex in certain conditions. (Note, these were not light weight barrels
so you can imagine what a light barrel will do.

I have seen slow motion video of super light barrels (#1 and #2 barrel contours) actually twisting due to the torque of the bullet tying to straightening out the rifling.



J E CUSTOM

 

[Dosh]

JE, does abnormal manufacturing stress affect the flex of a barrel and accuracy? Do you feel the McMillan, Manners and B&C stocks are vulnerable to barrel flex and if so is a proper brake the only fix? I've noticed with my Weatherby factory brake shots POI are lower than without it. As usual your points are very helpful. Thanks

 

[Deleted member 46119]

Barrel flex is a fact. Physics is physics.

Optimal Barrel Timing theory postulates that all barrels vibrate at the same frequency but profile affects amplitude.

JE's work shows that brakes can have an impact on barrel flex. IMO it does not affect the vibration propagation (frequency) only amplitude and harmonics, altering the barrel flex trajectory as the shock wave travels down the barrel. The barrel is still trying to flex.

on the other hand.

It's midnight, I'm tired after an evening of taking care of animals and making parts for my bandsaw so

I could be completely full of ....

 

[J E Custom]

JE, does abnormal manufacturing stress affect the flex of a barrel and accuracy? Do you feel the McMillan, Manners and B&C stocks are vulnerable to barrel flex and if so is a proper brake the only fix? I've noticed with my Weatherby factory brake shots POI are lower than without it. As usual your points are very helpful. Thanks

Barrel contours and discontinuities from the manufacture have a huge effect on barrel flex and also there shape (Contour, Straight taper, fluted and carbon wrapped). the one thing that I think all smiths would have to agree on is that the barrel shape/contour has to be uniform around the bore so harmonics are predictable and consistent.

Any attachment to the barrel can change this by disrupting the harmonics and making them uneven/inconsistent like a vented rib, sling swivel or a sight that is attached to the barrel on one
side.

A muzzle brake that is well balanced and installed correctly should dampen some of the vibrations/
harmonics and could change the poi. (But not necessarily for the worst) Most of the time there is a good chance that the group size will improve even if the poi has changed.

Stocks have a big role in managing harmonics. some stock materials resonate sound and some actually dampen, If bedded correctly the bedding can transfer the vibrations to the stock materials
for absorption reducing the barrel harmonics.

A barrel that flexes, can be very accurate as long as it is consistent, if the right load is found, but when you change that load accuracy and consistency can go out the window.

Accuracy is consistency, All things related to a weapon must be addressed in order to be consistently
accurate. This is where the re-loader has an advantage. He can tailor his load to get the most out of his weapon system.

J E CUSTOM

 

[Dosh]

JE, Fred, thanks for the input. Perhaps this is an area not addressed often when considering accuracy. Thanks

 

[hammer111]

Isn't barrel flex relative to the size of the cal, bullet , and powder charge.

Take the 300. If you shot a smaller bullet, with less powder. Wouldn't the flex be reduced also.

By developing optimal bullet weight , and powder and grain for your gun. You are managing flex.

It's seems the effects of porting are being redefined. Optimum porting placement and configuration will take accuracy to new levels.

Where does barrel dampening fit into this equation.

I wonder how much flex is in a 8 inch naval gun, or an Abrams.

 

[Deleted member 46119]

Isn't barrel flex relative to the size of the cal, bullet , and powder charge.

Take the 300. If you shot a smaller bullet, with less powder. Wouldn't the flex be reduced also.

By developing optimal bullet weight , and powder and grain for your gun. You are managing flex.

It's seems the effects of porting are being redefined. Optimum porting placement and configuration will take accuracy to new levels.

Where does barrel dampening fit into this equation.

I wonder how much flex is in a 8 inch naval gun, or an Abrams.

I've seen slowmo of 8in and M1A1 Abrams. They flex plenty.

AFAIK bore, profile, bullet weight and charge affect amplitude. Frequency is fixed. The OBT theory put into practical use is to get the bullet to exit the muzzle at the top of the wave just before flexing back down. AIUI Optimal Charge Weight does the same thing form manipulating a different parameter. With OBT, concentration is on velocity and bullet exit. In OCW concentration is on charge and reading the dispersion pattern, selecting the higher and more consistent range. Then fine tuning.