Magnum not inherently less accurate?

[Stan Taylor]

What about if the barrel had an absolute obstruction that stopped the bullet completely, absorbing its momentum. You see where I’m trying to go with this, right?

Here’s what I know will happen witnessing with my own eyes.
This is what happens when you. Have 2 bullets one behind the other .

 

[davidjoe]

Watching some of the shows on Outdoor Channel and others like Gun Stories, they are firing rifles and pistols at the range with everything in slow motion so you can see the bullet leaving the barrel. It has been confusing to me but I can clearly see that the bullet is out of the barrel before the rifle starts to recoil and pistols even more so. I know this disagrees with physics but there it is on film. Perhaps the bad shots from magnums are, as has been said here before, people being adverse to recoil.

There’s a channel called “Smarter Everyday” and another called the “Slow Mo Guys” on YouTube using equipment we will never buy for competitive shooting purposes, that can resolve motion much faster than bullet flight.

Current high speed photography equipment resolves cracks traveling through glass, in detail, to the edge of glass feet away, before the bullet that caused the crack has moved a quarter of an inch forward. These cameras resolve shock waves caused by individual powder grains burning after they left the barrel, across a wide field of view.

These channels have captured both 50’s and also cannon fire, - of the fuse lit wagon wheel variety where no one is either impinging on or creating movement. In the case of the cannons, the projectiles are getting very heavy in proportion to the cannon weight.

We see a jet of powder, then a projectile then more powder, shock waves and all, travel of the projectile maybe 5-8 feet from the muzzle, and then that cannon first starts its roll backwards, which continues for a number of feet.

There are many 50’s videos, including one by “Fullmag” that is called “Barrett .50 Cal Super Slow Motion” only 40 seconds long worth watching. I haven’t see one that demonstrates pre-exit recoil, only the opposite, and a lot of cringeworthy scope and barrel flexing, I will say the FullMag video shows the ever-so-slight movement of the spring-buffered barrel, pre-exit. Maybe 3% of its total movement. The rest of the rifle doesn’t start with it. That barrel is both short, fluted and light contoured, and the least the bullet would weigh is 650 and the most for that gun should be 750 grains, with 230 grains of powder.

I’m going to surmise that one of the 50 cal guys had pulled rearward on that .416 in anticipation of recoil, in Keith’s video . When you watch them fire a 50, as with other dedicated shooters, the barrel is just planted, dead still, then I see these brakes “explode” in flash and power, and then after that the motion starts to occur.

I mentioned it before, but Boyd’s recoil pressure curve, by definition of being the shape it is, increasing pressure over time, does proves that recoil is a “build” of pressure that intersects with inertia of a resting rifle, at some point, or actually not, if the gun is heavy enough. But prior to that intersection, if the barrel were to start moving, such as “immediately” which is inside first percent of the the primer’s ignition, then that law of physics would have to be disregarded.

 

[DickE]

Where would a barrel go if it had no threads?

 

[davidjoe]

Where would a barrel go if it had no threads?

Barrel threads per se weren’t in question. Whether an “endless” barrel, - one that trapped its own bullet by being long enough to do so, - or simply a “blind” bore that caught the shot, was used illustratively in the question of whether such a barrel would recoil at all, firing a shot. Opinions varied on when recoil occurs, but only one guy really ventured an opinion on this, specifically.

Such a barrel could pose a minor paradox. If it does not recoil despite the motion of the bullet and burning of the powder, that implies that recoil does not start until the bullet exits, as bullet and powder exiting are the only difference between an endless barrel and regular barrels. This would actually trump the assertion (which is true) that inertial resistance of the gun must be overcome before it moves at all.

Moreover, if it does recoil despite the fact that no material has actually exited it, that bends some assumptions about conservation of momentum and propulsion. Most pilots will tell you that absolute thrust reversers would of course prevent any forward motion in total, from still, as would the inability of exhaust to ever exit a jet engine. Likewise, if exhaust exited a small jet engine attached to a mount affixed inside an airtight shipping container, the mount will experience torque but the container is simply going to experience increased air pressure as fuel becomes gas, not be motivated to move. There is a nozzle being studied with a “blind” end preventing exit, which some physicists label the impossible engine for obvious reasons. Its proponents under a research grant suggest that microwaves reflected internally within that nozzle a certain way, will generate small forward thrust despite the absolute exit blockage.

The original closed barrel hypothetical must reconcile with the accepted idea that you must push against something else, in order to move, -I’m thinking of the untethered, helpless astronaut here, - or as the saying goes, one cannot lift himself up by his own bootstraps. But I do think at first blush, a fully contained barrel moving on its own is not a very likely exception to constraints applicable to similar objects. The only thing a rifle bullet pushes against not contained by or attached to the gun, before the bullet exits the “system” is the ambient air in the barrel. Perhaps this is sufficient to account for some slight motion, but that would not be for the reason that the rifle is offsetting the momentum of the bullet.

If guns don’t actually recoil until the bullet has exited, or if most guns are too heavy to start their recoil until the bullet has exited, either one of these would represent a big difference in the conventional thinking on the subject. This would not suggest the barrel does not vibrate before it recoils, whenever that actually is on a specific gun.

 

[INTJ]

Most pilots will tell you that absolute thrust reversers would of course prevent any forward motion in total, from still,

I can say, with near absolute certainty, that no pilot would tell you that. Maybe an engineer would. A pilot would simply tell you that he could back up on the ground using reverse thrust, aka C-130s and C-17s. Oh yeah, the 130 guy would also tell you not to reverse in the air. The C-17 guy would be okay with it.....

 

[INTJ]

Where would a barrel go if it had no threads?

It would go in the lathe to be threaded......

 

[BoydAllen]

Where would a barrel go if it had no threads?

Decades back, a fellow that I knew blew up a rifle rather spectacularly, to the extent that the top half of the receiver ring came off the action. The barrel went down range a bit. It was a Savage 110 and the shank of the barrel was deformed, swelling so that the barrel nut could not be removed.

 

[BoydAllen]

There is other potential for barrel motion besides recoil. Have you ever watched a hose move when the valve is turned on , with a hand vlave on the end that is shut? With heavier bullets and greater gas volume for a given bore size one might postulate that the effect would be greater, and this might affect accuracy. One thing that we do know is that in the real world, with shoulder fired arms, higher recoil rifles are more difficult to shoot accurately. That is the main reason for weight limits in competition. Years ago, my first CF rifle was a sporter weight .308 that only liked heavy bullets. I shot it, from a rest, with light shoulder contact, and no other contact. It would bounce off the front bag as it was fired. The concentration required to ignore all of the motion was good training. I had to learn to focus on the target, slowly increase pressure on the trigger, and not react. My .22 RF was much easier to shoot. No bounce, minimal recoil. I think that this comparison speaks to the original question. Harold Vaughn pointed out that a rifle rotates around its center of mass as it is fired, due to the usual offset between line of thrust and center of mass. Strictly speaking this movement is different from recoil. If you eliminate the offset, the effect is minimized. He did actual testing on this. I think that it is obvious that very slight differences in muzzle elevation are significantly magnified at the target.

 

[davidjoe]

There is other potential for barrel motion besides recoil. Have you ever watched a hose move when the valve is turned on , with a hand vlave on the end that is shut? With heavier bullets and greater gas volume for a given bore size one might postulate that the effect would be greater, and this might affect accuracy. One thing that we do know is that in the real world, with shoulder fired arms, higher recoil rifles are more difficult to shoot accurately. That is the main reason for weight limits in competition. Years ago, my first CF rifle was a sporter weight .308 that only liked heavy bullets. I shot it, from a rest, with light shoulder contact, and no other contact. It would bounce off the front bag as it was fired. The concentration required to ignore all of the motion was good training. I had to learn to focus on the target, slowly increase pressure on the trigger, and not react. My .22 RF was much easier to shoot. No bounce, minimal recoil. I think that this comparison speaks to the original question. Harold Vaughn pointed out that a rifle rotates around its center of mass as it is fired, due to the usual offset between line of thrust and center of mass. Strictly speaking this movement is different from recoil. If you eliminate the offset, the effect is minimized. He did actual testing on this. I think that it is obvious that very slight differences in muzzle elevation are significantly magnified at the target.

I agree with you 100% on there being a variety of disturbances and sources of motion traversing the barrel. Yes, I definitely do think the bullet sends a pressure wave out in front of it, and also that harmonic waves could travel several times down the length of the barrel by the time of exit. How much violence we do to our prized barrels is pretty unsettling. We know they must deform and snap back like brass does, because an external strain gauge placed on them can translate the displacement to psi, and we know the unhappy fate of all brass.

One thing I definitely didn’t want to appear to contradict in any way is the well-understood and accepted functioning of tuners, which bear upon motion through the barrel that precedes exit, and proves the significance of that other motion on accuracy.

 

[Edd]

I have read that measured muzzle velocity will be different with different people shooting the same rifle and ammo. If this is true, it seems it would prove that some of the energy used to push the bullet forward is pushing the rifle rearward while the bullet is still in the barrel.

 

[davidjoe]

I have read that measured muzzle velocity will be different with different people shooting the same rifle and ammo. If this is true, it seems it would prove that some of the energy used to push the bullet forward is pushing the rifle rearward while the bullet is still in the barrel.

I’m going to try to smoke some pilots out of the eaves again, but that’s proving hard to do .

This theory or principle you describe would have to work the same way going forward and backward.

Looking at an A-10 Warthog with its big 30mm, we know that the rapid fire chain gun’s recoil is significant and slows the plane dramatically.

The first rounds fired at say 1,000 MpS leave at that speed plus the speed of the plane in that direction, a second or two later in the burst the plane has slowed, but scores of rounds were shot.

Those first rounds, judged from the ground hit harder and travelled faster (factor out that the gun gets closer to the target) than subsequent rounds, say by 10%.

It would not be correct to conclude early rounds penetrating deeper had higher ME or caused more recoil; the end of the barrel sees them all leave at the same V, but a ground radar near the target trained just 3 inches in front of the barrel is going to report each round going slower than the one before it, (because the plane slows) and both are correct. But, the rounds were charged with exactly the same powder and bullets and were shot from the same barrels, recoiling the same.

The 30’s hit at different speeds because the gun was moving differently, shot to shot. I’d surmise that people can affect the velocity of a bullet on target.

(Some shooters lean forward involuntarily. You see this when the gun doesn’t fire but they expected it to. Some slap the trigger back, either with or without palm wrap, others intentionally start the gun on the arc or line they expect it will need to travel, which is easier on the body. In the tests you reference, we don’t know how much different velocity was).

But just like with the A-10, they
moving the whole gun slightly differently, but the interplay between the bullet and barrel would result in the same outcome every shot if they were not.

Edit: Also, I think about it this way, if their moving the gun is not the explanation for different velocity, then they are necessarily somehow affecting the internal pressure inside the barrel. To my thinking, if the bullet is gone, these are the only two ways that velocity can altered at the point that firing occurs, and that second possibility I can’t see happening.

The third possibility is of course the bullet moving the gun itself before exit, if the gun is allowed to move, if this occurs. I saw a video last evening of multiple guns recorded that shot a “squib load” which stuck in the barrel, and of course those guns were put down immediately, as there was now a deadly obstruction should another shot be fired. The point of that video was to warn shooters, but that kind of video may also show whether there is even slight recoil or not occurring pre-exit.

It would be very interesting to see whether an F-Open rifle shot different velocities from a machine rest versus string pull free recoil on the bags, though, and that would certainly be easier than trying to film the bullet’s exit. However, high speed photography does reveal how much gas blow by is occurring and the shock wave size of the ambient barrel air, both which would have the same apparent effect as the recoil we are talking of.

.22 barreled actions are clamped routinely for lot testing, effectively making them a gun of hundreds of pounds that a .22 charge cannot budge. It might be interesting to know what Lapua and Eley would say about whether this increases muzzle velocity.

As an Open shooter, my guess is that you won’t see a difference in velocity but you will in accuracy, for the reason that other movements besides recoil affect accuracy.

 

[Old Navy]

But the mosquito, traveling at ~450 times faster than the speed of light creates what kind of energy singularity that vaporizes the truck?

That's a BEER:30 question!

 

[Old Navy]

I wasn't going to post on this topic because it made my head hurt. Now I know there are some old dudes here that remember back in the day when everyone hunted with an 06, .270 etc etc. I can remember sighting my trusty 30-06 in to impact approximately 2 1/2" 100 yards with 150 grain deer loads. Now along came elk season and it 180 grains back then. With no sight change they impacted quite a bit higher. The gun writers of the day said it was simple. Bigger slower bullets took longer to exit the barrel. This was back in the 70s so maybe my memory is a little foggy.

 

[Archer79]

The 300wsm currently holds the 1000yd benchrest world record for small group...its under 3" for 10 shots

 

[davidjoe]

The 300wsm currently holds the 1000yd benchrest world record for small group...its under 3" for 10 shots

It’s just an aside, to a wrinkle, on what’s merely quizzical, but I have always thought magnum was a suspect term. The list of .30 cal cartridges in ascending capacity, probably has as many “magnum” labels affixed as standard.

Weatherby for example has two long action 30’s of nearly the same COAL, that it markets for hunting purposes, that are both callled magnum. If anything, the 30-378 sometimes leaves off the magnum, while the much smaller capacity 300 Weatherby Magnum, never does.

The 30-378 also held a BR record for 30 years, and deserves the name, according to articles, testing by or for the military, reached 6,000 FPS with it.

 

[davidjoe]

I wasn't going to post on this topic because it made my head hurt.

Mine too, because as simple as it seems, video is colorable either way, and,

1) When if ever in the process is this properly seen as one instead of two objects;

2) The barrel pre-exit has traits of just a basic pressure vessel;

3) The bullet while in the barrel has traits of a pendulum in a grandfather clock (one self-contained object) trying to move the clock, in the opposite direction conserving momentum;

4) But unlike a pendulum, the bullet is not connected to the barrel, (Jelenko’s two object frictionless bullet, the clearest image of opposing recoil);

5) The bullet on exit has traits of ejecta, but with mischief causing recoverable energy;

6) The barrel and cartridge has the functional traits of a both a rocket engine and nozzle;

7) but the barrel isn’t passive because it resists the exit of the bullet, and under some circumstances can also recover it.

 

[Warren Dean]

 

[Archer79]

It’s just an aside, to a wrinkle, on what’s merely quizzical, but I have always thought magnum was a suspect term. The list of .30 cal cartridges in ascending capacity, probably has as many “magnum” labels affixed as standard.

Weatherby for example has two long action 30’s of nearly the same COAL, that it markets for hunting purposes, that are both callled magnum. If anything, the 30-378 sometimes leaves off the magnum, while the much smaller capacity 300 Weatherby Magnum, never does.

The 30-378 also held a BR record for 30 years, and deserves the name, according to articles, testing by or for the military, reached 6,000 FPS with it.

For what it's worth P.O. Ackley referred to the 243 winchester as a magnum case when he was asked about improving it

 

[davidjoe]

Warren, that there looks like an animal that can effortlessly copy my words, has 20 : 1, 270 degree, high contrast vision, can live 85 years on a few 50 pound seed sacks, for crying out loud, can fly, … saying, hey turd target, this ain’t all that complicated, about right? Or, that’s internet for giving the bird .

 

[BoydAllen]

The disagreement that I have with the OP is the timing of the beginning of recoil relative to the bullet exiting the barrel. All sorts of wild visualizations have been offered but no one has addressed my example of what happens when one mistakenly places a rifle's front sling stud in the center of the front bag. If the rifle did not move until the bullet cleared the muzzle, this would have no effect on accuracy. It does, and this particular test is one that requires no exotic equipment. Anyone who has an accurate rifle with a sling stud mounted on the forestock can duplicate it. As far as the question that became somewhat secondary. Yes, a .300 WSM has shot the pending new 10 shot record for 1K.

Sunday GunDay: .300 WSM Pending 1K World Record Heavy Gun « Daily Bulletin

This Sunday we feature an impressive .300 WSM Heavy Gun shot by a superb long-range shooter. With this rig, at age 83, Arizona benchrest ace Charles Greer drilled a remarkable 2.862 100-10X group, beating all known 1000-Yard HG 10-shot records on the books.

bulletin.accurateshooter.com