[Silver_Is_Money]

This is my initial attempt at establishing a formulated means:

(LB2/LB1)^(1/3)*VB1 = VB2

Where:
LB1 = Effective Length of Barrel 1 in inches
LB2 = Effective Length of Barrel 2 in inches
^ = Raised to the exponent power of
* = multiplied by
VB1 = Velocity measured in Barrel 1
VB2 = Velocity estimated for Barrel 2

NOTE: The exponent value of 1/3 as seen here is merely an initial estimate. This exponent value can (and likely must) be varied whereby to hone in upon greater precision.

NOTE #2: Effective Barrel Length is measured from the crimp position of the shell within the chamber to the muzzle.

 

[DougMO]

Or you can add 6fps per inch according to the Lymans manual

 

[Silver_Is_Money]

Note #3: It is inherently to be presumed that the chamber dimensions and bore diameter and choke constriction for Barrels 1 & 2 are identical. As any variation witnessed here can introduce some unknown small measure of difference in velocity.

 

[Der Verge]

This is my initial attempt at establishing a formulated means:

(LB2/LB1)^(1/3)*VB1 = VB2

Where:
LB1 = Effective Length of Barrel 1 in inches
LB2 = Effective Length of Barrel 2 in inches
^ = Raised to the exponent power of
* = multiplied by
VB1 = Velocity measured in Barrel 1
VB2 = Velocity estimated for Barrel 2

NOTE: The exponent value of 1/3 as seen here is merely an initial estimate. This exponent value can be varied whereby to hone in upon greater precision.

NOTE #2: Effective Barrel Length is measured from the crimp position of the shell within the chamber to the muzzle.

It doesn't work that way, as in direct proportion to barrel length. There are some generalized observations made over the years concerning certain cartridges and the effect of barrel length, but they are all just that. 6 fps/inch for shotguns. 25fps/inch for .223 (whatever it actually is, this is just an example for argument sake), but that changes dependent on exactly how long the barrel is.
Additionally, longer barrels don't always increase velocity. Powder changes are required when you get to extra long barrels. For example, I have one .22, 18" barrel that is about 80fps longer than my other .22 with a 24" barrel.

 

[Silver_Is_Money]

Raising to an exponent is not direct proportion to barrel length. Merely stating a static increase per inch (as for 6 FPS) is an example of direct proportion to barrel length. Acceleration is exponential. Acceleration effectively ceases at the muzzle.

If you measure zero FPS before ignition and 1200 FPS at muzzle exit, then try subtracting 6 FPS per inch back to the crimp position and see if you compute zero FPS.

 

[reyper]

Really think you’re over complicating an issue that is pretty irrelevant to practical every day shotgun shooting. Good luck though and good shooting, Rey

 

[DEG]

YES you can in fact predict the velocity from another shotgun barrel based on the measured velocity from another barrel within the standard of "close enough". Stop overthinking things and go shoot.

 

[Multiflora]

Good question.

Most common path to discovery:
Compare based upon......Barrel length(in meters)/Bore Diameter(in meters) - [Human Boredom % X (Smoke+Mirrors)]/Gullibility Factor to the FunSucked exponet(see table) will yield an answer.

 

[noweil]

A formula like this could help me to calculate my perfect lead when I shoot guns with different length barrels.

 

[DEG]

A formula like this could help me to calculate my perfect lead when I shoot guns with different length barrels.

Yea, I'm working to invent a range finder that you can program in your shell ballistics data and barrel length. Then you click a button and use it to watch a target fly and it calculate the exact speed and trajectory of the target will tell you breakpoint and lead. e.g. "Shoot 32.7 yards from trap leading 5.3 feet ahead and 1.2 feet below".

If this works, I'm planning a model that mounts to the bottom of your gun with jet thrusters that will move your barrel to the correct lead and pull the trigger at the proper break point.

 

[AHI]

No you can not . I have chronographed the same load in different guns . With the same length barrel length. Every one of them averaged a different velocity. Time to SUAS.

 

[Silver_Is_Money]

No you can not . I have chronographed the same load in different guns . With the same length barrel length. Every one of them averaged a different velocity. Time to SUAS.

See Note #3.

 

[Silver_Is_Money]

Since I'm the life of the party today:

All else being equal:
P2 ~=( C2/C1)^2 * P1
(where C1 and C2 are powder charge weights for specifically the same powder)
(and P1 and P2 are chamber pressures)

All else being equal:
V2 ~= (C2/C1)* V1*Some_FPS_Constant
(where V1 and V2 are velocities)
(and where 'Some_FPS_Constant" appears to "potentially" reflect the relative energy content, or loosely the burn rate position, of the powder)

 

[Multiflora]

Since I'm the life of the party today...

I believe you are misreading and so, misinterpreting the data gathered.

 

[Silver_Is_Money]

I believe you are misreading and so, misinterpreting the data gathered.

I actually derived these 'nominal' relationships by observing published Hodgdon load data.

 

[Rooster booster]

A formula like this could help me to calculate my perfect lead when I shoot guns with different length barrels.

😂👍🏻

 

[Drew Hause]

Sure.
Other than this; per SAAMI
"Load velocity can vary by +/- 90 fps for both game and target loads."

 

[Multiflora]

I actually derived these 'nominal' relationships by observing published Hodgdon load data.

That would not be the data to which I referred.

 

[noweil]

Sure.
Other than this; per SAAMI
"Load velocity can vary by +/- 90 fps for both game and target loads."

I can tell by recoil when the velocity is different. However, since it is too late to adjust my lead after feeling the recoil, I miss.

 

[DougMO]

I’ve been working on feeling that increased velocity and adjusting to compensate while the shot is traveling down the barrel. Reaction time is critical. If I swing too fast I spread out my shot string sideways.