Barrel length and muzzle flip

He doesn't know what he is talking about.

All other things being equal; the same loads and the same shooter and the same technique, a heavier barrel will have less muzzle flip than a lighter barrel.

AFAIK, he's actually technically right, but IMO, the effect really only starts to show when things really speed up. That, and many may confuse perceived recoil with actual muzzle flip.

Most wont be able to tell the difference, but speed things up to, say 0.2sec splits, and my bet is a really good wheelgunner would get 5 rounds off slightly faster with the 3" SP101 than with the 4" (and certainly faster than with a 6" gun), but those from the 4" gun benefited from a slightly longer sight radius, so they're a bit more likely to have hit CoM.

OK, so there is a longer lever provided by the longer barrel but the angle of the exiting bullet is much higher over the axis of rotation in a short barrel than in a long one.
For example; say a short barrel ends at a 45 degree angle above the wrist (the axis of rotation) and compare that to a 4” barrel ending at a 30 degree angle over the axis. (I’m just pulling these angles out of the air to illustrate my point).
In the case of the 45 degree angle above the axis, the force vectors are split evenly between the rearward vector and the upward vector. In the case of a 30 degree angle, only a third of the force is the upward vector while 2/3 of the force is the rearward vector.
The length of the barrel as a lever is insignificant but I am also ignoring the inertial force imparted to the gun and wrist while the bullet moves from the chamber until it’s exit from the barrel.

IMHO Mr Broland is right as usual.
I seem to feel a wee bit more "flip" shooting the same loads from a 6" barreled K-14 than from a 2" barreled K-15 (possibly due to the mechanical advantage mentioned above) although perceived recoil is certainly partly compensated by the extra barrel weight.

For faster shooting,I get my best results with a 4" barreld K-15 or 586.
I do doubt the difference between a 3" and a 4" barrel would be noticeable, though.

9mmepiphany said:

The bullet, after being fired, will spend more time in a longer barrel...just based on the length of barrel. Since the rotation (rise) is continuous from the moment the bullet leave the case, wouldn't spending longer in the longer barrel result in it having risen more before the bullet exits the muzzle?

Also, since the bullet spends a longer time in the bore, the gas would have longer to push back above the pivot point

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When all else is equal, "time" is a proxy for barrel length, so 9mm's 1st statement is correct. The 2nd can easily be overgeneralized, though:

The physics works out such that "intrinsic recoil"* is time-independent, and the amount the muzzle moves while the bullet's in the barrel (and therefore enacting a force on the gun) is only dependent on the mass of the gun, the mass of the bullet/powder, and the barrel length. Time (and therefore velocity) doesn't matter: While a faster bullet will spend less time in the barrel, it raises the muzzle faster, but for less time. That distance the muzzle rose, then, is the same as the slower bullet (which raised the muzzle slower, but for more time).

Also, the mechanical leverage the exiting bullet has occurs at the end of the barrel. The longer barrel has more mass there, and ought to be more resistant to the leverage. But the longer barrel comes with more "intrinsic recoil", and since it gets the muzzle moving before leverage effect, it theoretically boosts the leverage effect a bit.

Again, though, these aren't major effects and won't be noticeable under most conditions. Still, if I were going to scope a target pistol, I'd go for a shorter, rather than longer barrel.


* what I call the upward movement of the muzzle while the bullet's still in the barrel.

"won't be noticeable under most conditions" +1

Whew! Too complicated for my simple mind.

Let's do a hypothetical.

Let's levitate a muzzle loading barrel into the air so there's no pivot point at the rear.

Let's not taper this barrel, so there won't be a rearward weight bias. Let's add a small weight at the muzzle in order to counter the mass of the breechblock.

Fire it.

Will the muzzle rotate upward...or will the thing recoil straight backward? Will it matter how long the barrel is or how fast the bullet exits?

1911Tuner said:

Will the muzzle rotate upward...or will the thing recoil straight backward?

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Since there's no pivot point in this hypothetical, the barrel will be pushed straight back, methinks.

But how 'bout an experiment than can be done:

Stick a 3" N-frame and a 6" K-frame in a ransom rest, such that the gun is free to rotate upon firing. I'm guessing the guns would be about the same weight, so they'd differ in barrel length only. My bet is the 6" gun shoots the same ammo a bit higher.

Then choose one of them, and vary the ammo:
- Same bullet weight, different velocities, and my bet is they hit about the same POI.
- Same velocity, different bullet weights, and my bet is heavier bullets hit higher.

I have to side with those that think this conventional wisdom, that longer barrels recoil less, is wrong. I had this conversation with a well known gunsmith and we both agreed that longer barrels "seem" to have more leverage against the wrist and that shorter barrels are less wrenching. I think shorter barrels are louder with more obvious muzzle blast and that is the reason for the misconception.

Since there's no pivot point in this hypothetical, the barrel will be pushed straight back, methinks.

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Yes, it 'twill.

The muzzle flips precisely because there is a pivot point AND because the bore axis is above the pivot. In the case of revolvers, the hand is the pivot point. It's also an outside force that decelerates the back end while the front end is free to move.

Think of a bullet's yaw when it hits a fluid medium. The nose hits the outside force, but the base hasn't.

But how 'bout an experiment than can be done:

Stick a 3" N-frame and a 6" K-frame in a ransom rest, such that the gun is free to rotate upon firing. I'm guessing the guns would be about the same weight, so they'd differ in barrel length only. My bet is the 6" gun shoots the same ammo a bit higher.

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Yep...at least theoretically. The bullet is in the barrel for a longer time. The gun starts to rotate around the pivot point as soon as the bullet starts to accelerate...so naturally, the bullet from the longer barrel will strike higher...the same as a heavier, lower velocity bullet will from the same gun. Dwell time in the barrel.

But the barrel's length doesn't cause the muzzle to flip any more or any less. The longer barrel's extra weight will tame the muzzle flip a little...which leads to another question.

Will the more rapid muzzle rise with the shorter barrel work to cancel out the bullet dwell time in the longer barrel and make any difference in the impact point a non-starter?

Now, here comes the theoretical part.

Or...Will the more rapid rotation of the shorter, lighter barrel actually cause the bullet to impact higher?

These theories are going to be very hard to prove because of the tiny increments involved. It would necessarily entail using a machine rest to shoot groups instead of single shots with an accurate gun and precisely loaded ammunition.

A few years back, I had a Model 29 Mountain Gun and a standard 4-inch Model 29. Firing ammunition from the same lot, the difference in recoil was...very noticeable...especially in the violence of the muzzle flip. I'm not at all recoil sensitive, but after two cylinders full of my old standard consisting of a 245-grain cast bullet and 22 grains of 2400, I was done. I had a friend who shot two rounds...laid the gun down on the bench...and refused to shoot it again. With the standard M29, he was good to go. That thing was a beast with a full-throttle "Elmer" load.

1911Tuner said:

the same as a heavier, lower velocity bullet will from the same gun. Dwell time in the barrel.

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It's not intuitive, but I don't believe it's "time" per se, but barrel length: The length the bullet travels is proportional to the distance (length) the gun gets pushed back.

Solve the equation for Conservation of Momentum (mass x velocity). Velocity is, of course, distance/time. The time the muzzle spends getting pushed back is the same as the bullet dwell time, so "time" cancels out, and the equation really becomes Conservation of "MD" (mass x distance). Ergo, just the mass of the gun, mass of the bullet/powder, and the barrel length matter. Dwell time and velocity don't.

1911Tuner said:

Will the more rapid rotation of the shorter, lighter barrel actually cause the bullet to impact higher?

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Sooo...my answer is maybe. If the mass of the shorter-barreled gun is less than the longer-barreled one, it could hit higher because the bullet is pushing against less mass, and the muzzle therefore jumps more.

But in my example above, I intentionally used the example of a short-barreled N-frame and a long-barreled K-frame to keep the weights roughly the same. Get the masses the same (with similar CGs), and the shorter-barreled gun won't hit higher; the longer-barreled gun will. Adjusting the loads such that the dwell times are the same won't make a bit of difference, I predict.

This is the first time I have ever had to read a thread three times to fully understand the discussion. I always assumed basics, that longer barrel meant more weight, and thus less recoil.

I see now there is more to it. Very interesting and good explanation MrBorland. I learned something in this one.

question:

Sooo...my answer is maybe. If the mass of the shorter-barreled gun is less than the longer-barreled one, it could hit higher because the bullet is pushing against less mass, and the muzzle therefore jumps more.

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Wouldn't the reduced velocity (due to the shorter barrel), and thus a more arched trajectory of the slower moving bullet have some effect on this too, and negate the above mentioned outcome? I suppose you'd need to be shooting a pretty long distance to really notice or measure this. Obviously the recoil impulse would have the effect you describe due to the gun weighing less, i.e. same force working on a less massive object, but I'm just curious about the impact point.

the smaller the radius (barrel length), the faster the rotation (muzzle flip) for a given amount of energy.

the increase in weight of the longer barrel should negate an increase in velocity (and therefore energy), so cancels out (sort of).

so, i say the shorter barrel will "flip" more than the longer barrel.

murf

Sooo...my answer is maybe.

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There ya go. Until it's actually tested and proven...it's all guesswork and theory. And even testing in a machine rest can't duplicate what would happen in actual shooting from one man to the next. As a competitive revolver shooter, you know as well as anybody the effect that grip strength and recoil control have on the point of impact...because with a real gun in a man's hand, recoil and muzzle flip start the instant the bullet starts to accelerate...not when the bullet is about to exit the muzzle.

The whole point of my hypothetical suspended gun barrel was to illustrate that the bullet can't "lever" the barrel upward, regardless of the length. All the forces are horizontal. (If we ignore the rotational forces and torque imparted by the rifling.) There's no vertical force to cause the muzzle to lift unless there's a pivot at the rear of the gun, and the higher the bore axis is above the pivot point, the greater the amount of rotation with a given gun/cartridge combination.

1911Tuner said:

And even testing in a machine rest can't duplicate what would happen in actual shooting from one man to the next. As a competitive revolver shooter, you know as well as anybody the effect that grip strength and recoil control have on the point of impact...because with a real gun in a man's hand, recoil and muzzle flip start the instant the bullet starts to accelerate...not when the bullet is about to exit the muzzle.

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Agreed.

My follow-up discussion on the OPs questions is really one of those "how many angels can fit on the head of a pin" discussions. As you suggest, there's much more to "shootability" beyond what's been discussed here. One of these days, I'd like to get hold of a ransom rest and do some testing, though. Just 'cuz.

My follow-up discussion on the OPs questions is really one of those "how many angels can fit on the head of a pin" discussions.

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I don't know if it's that insignificant, there's always discussion going on involving statements that longer barrels produce less felt recoil. It might be nice to have some data to support any seat of the pants impressions.

One of these days, I'd like to get hold of a ransom rest and do some testing, though. Just 'cuz.

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Keep us posted on your findings. I haven't had access to a Ransom Rest in years. I miss it.

I've had one for a year but have never set it up.

He doesn't know what he is talking about.

All other things being equal; the same loads and the same shooter and the same technique, a heavier barrel will have less muzzle flip than a lighter barrel.

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That's correct. I shoot .45 Colt loads of around 21,000 PSI in my Colt New Service with a 7 1/2" barrel, and it's a pussycat. The same load in a Ruger with a shorter barrel has a lot more flip.

I have a pair of custom Ruger Bisley .44Mag's. Same gripmaker, same grip profile, apart from cosmetic differences, they are the same except for barrel length. I've always found the 4 5/8" barrel version more comfortable to shoot than the 7½".

The same load in a Ruger with a shorter barrel has a lot more flip.

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Ruger what? You can't directly compare a DA to an SA because they handle recoil differently.