Magnum not inherently less accurate?

[Warren Dean]

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 .

Nah...just finding this thread a real hoot to read.

 

[sdean]

Nah...just finding this thread a real hoot to read.

Did we learn anything about making a wind call? That’s all I need.

 

[davidjoe]

The disagreement that I have with the OP is the timing of the beginning of recoil relative to the bullet exiting the barre. 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

A test like that seems like it could be prone to both false positives and false negatives.

For example placing the sling stud in the center of the front bag is almost certain to exacerbate the effect of torque by making the rifle rifle more tippy. It will also depress itself into the bag creating an anchor that means whatever effect that trigger pull weight and the shooter had had on moving the gun pre-fire, it is now lessened. These POI changes would not be recoil dependent.

Conversely, you could have a false negative by putting the stud there, but using a heavy gun and light ammo combination that doesn’t demonstrate any effect at all, even if you are right that it can be seen in other guns. You could also have a false negative by unknowingly using different shoulder pressure each shot in an amount that masked the stud.

******
I’ve been thinking, how would we discern if a particular heavy target rifle recoiled before the bullet left the barrel? I’ll assume we don’t want to purchase any specialized electronic equipment.

The safest method I come up with is you’d (“you” of course, always means a “trained professional in a testing tunnel”) shoot paper, in a controlled environment. We always shoot paper, but no, you’d shoot a sheet paper that’s 100% flat up against the muzzle of a gun, one that’s set up so it won’t recoil. You’d do this multiple times keeping each sheet as a reference. Hopefully, there’s going to be neat holes with a roughly consistent char and residue. Mind you, I haven’t done this, it’s a thought experiment.

Then, you shoot a sheet of paper, a number of times, say 1/2 inch from the muzzle, same machine rest. Almost certainly these sheets will be ragged by comparison.

Now you have two baselines of what paper looks like at two distances. Proceed to forgo the machine rest and shoot the gun normally with paper against the barrel. If the thought experiment works, sheets of paper in normal shooting are going to look more like either set “A” or set “B” and you’ll now have an idea of whether a specific gun recoils or not before the bullet leaves the barrel.

We do know that target rifles all recoil and continue to expel burning powder, so a level of fine discernment in what you are looking at would have to be employed. For paper that didn’t bow forward at bullet exit, from catching powder, the side opposite the muzzle will accumulate more residue. It is possible to avoid this “tainting” of results by devising something of small bent paper, that will fall off the barrel end if it recoils, but if it does not recoil, will be be witness marked by the bullet as it passes. But that is getting into areas that are going to invoke Darwin’s principles, and so I’ll shut up on that count, but it’s possible, in the enclosed facilities of trained professionals, by them, of course, inquire there or with Myth Busters if interested.

 

[Ken]

My science is:
More recoil =more flinch=worse group.

 

[Mr. Ten-X]

No question to how accurate the magnums are. Look at all of the long-standing 100 & 200 yard benchrest records held by them.

 

[Warren Dean]

No question to how accurate the magnums are. Look at all of the long-standing 100 & 200 yard benchrest records held by them.

Yep...and Mid Tompkins winning at Perry with a 300 Winchester Magnum in the 60s

 

[dave@aDave]

In nuclear power school we one calculated the velocity needed by a mosquito to stop a tractor trailer moving 70 mph, assuming an inelastic collision and no deformation.

When did you go to nuclear power school?
I went in 1965 and this was an exercise then.

 

[INTJ]

I have a great illustration of how a "magnum" and accuracy interrelate.

After several of us with 6 BRAs were blown off target at the 2018 NBRSA regionals, I decided to build a 300 WSM for LR BR. Several years earlier I had used a 300 WSM in 1K BR with good success.

Now the 300 WSM isn't really a magnum, but it does have double the case capacity of the 6 BRA.

So I built a 300 WSM 17 lb light gun. I did a good job on the chamber. My first 600 yd match with it I shot in a relay where a storm blew through. While I did shoot small group of the match, I didn't really get any useful info. Also, after the match when I went to remove the muzzle brake the whole barrel unscrewed. So my first BR "magnum" lesson was to torque the barrel to at least 60 ft lbs.

The second match was the real test. I shot first relay in an NBRSA 600 yd match. While I won the entire match for score, I was last in my relay for group. The reason was the 17 lb 300 WSM moved about three times as much under recoil vs a 17 lb 6 BRA and I just couldn't shoot it fast enough in good conditions to keep up with the 6s. In LR BR, to have good groups you must be able to shoot quickly to keep all your shots in the same condition.

So I concluded that the 300 WSM probably wasn't a good choice as a LG in 600 yd BR. Now Bill Johnson's 70 lb heavy gun in 300 WSM was very competitive at 600 yds. So I decided to stick with the 6 BRA for LG and build a 300 WSM HG.

My HG weighs 30.5 lbs. It recoils about as far back as the 6 BRAs, maybe a tiny bit more, but I can shoot it as fast as a 6 BRA LG. I have only shot it in IBS 1000 yd matches but it shoots well. Not as good as a 6 BRA when the conditions are good, but in average to poor conditions it seems to have an advantage. The 300s seem to score better than the 6s in most conditions.

A good illustration is the first match where I shot the 300 WSM HG. Both days I shot the second best group and score. Day one was a 4.33" 100-5x, and I think I was beat by a 300 SAUM IMP. The second day was outstanding conditions. I shot a 3.855" 100-3x, but was beat by a 6 BRA that shot a 2.695" 100-something X world record.

BTW, the smallest group and highest score ever shot in any 1000 yd competition was shot earlier this year with a 300 WSM. It was a 2.6 something 100-10x.

 

[SweaterDood]

Lots of posts, not enough time...

Had not seen this explanation yet, so:

Recoil starts at ignition. Equal/opposite stuff. The next bit is key in my mind. As the pressure builds and gas expands, the pressure vessel grows as the bullet travels forward. As a pressure vessel applies a uniform amount of force in all directions, the center of the vessel must travel forward to remain central of the vessel. Equal/Opposite forces and resistance come into play here as the rifle and bullet both resist the movement of the center of pressure. The 22lb rifle versus the .0307lb (215 Berger) have very different amounts of resistance. The bullet also has the aid of rifling friction, which can be treated as negligible, so long as the bullet escapes.

To the OPs other question about an infinitely long barrel, the rifling will eventually slow the bullet back to stationary, as will the vacuum created by a negative pressure as the gas expansion ceases and the bullet temporarily remains in motion. The slowing of the bullet will act as a brake to end the recoil but will not return the rifle to its initial position, because the bullet & powder/gas are no longer in the same position as before charge was lit. In this hypothetical scenario, the center of mass (assuming a perfectly linear recoil) should remain the same, because of the closed system principle.

This would be the same as if you were in a cargo van and pushed off a seat back to propel yourself to the rear before hitting the back doors. The van would move to account for the change in center of mass. Another way to think about the shift in center of mass is with the closed system of a person on a motorcycle. While balanced and stationary, the rider can thrust their body to push/pull the bike a small amount. The motion of the system on a flat surface is a direct correlation to the change in center of mass.

I hope there was some value somewhere in there...

 

[XTR]

When did you go to nuclear power school?
I went in 1965 and this was an exercise then.

Class 82-04

 

[BoydAllen]

A test like that seems like it could be prone to both false positives and false negatives.

For example placing the sling stud in the center of the front bag is almost certain to exacerbate the effect of torque by making the rifle rifle more tippy. It will also depress itself into the bag creating an anchor that means whatever effect that trigger pull weight and the shooter had had on moving the gun pre-fire, it is now lessened. These POI changes would not be recoil dependent.

Conversely, you could have a false negative by putting the stud there, but using a heavy gun and light ammo combination that doesn’t demonstrate any effect at all, even if you are right that it can be seen in other guns. You could also have a false negative by unknowingly using different shoulder pressure each shot in an amount that masked the stud.

******
I’ve been thinking, how would we discern if a particular heavy target rifle recoiled before the bullet left the barrel? I’ll assume we don’t want to purchase any specialized electronic equipment.

The safest method I come up with is you’d (“you” of course, always means a “trained professional in a testing tunnel”) shoot paper, in a controlled environment. We always shoot paper, but no, you’d shoot a sheet paper that’s 100% flat up against the muzzle of a gun, one that’s set up so it won’t recoil. You’d do this multiple times keeping each sheet as a reference. Hopefully, there’s going to be neat holes with a roughly consistent char and residue. Mind you, I haven’t done this, it’s a thought experiment.

Then, you shoot a sheet of paper, a number of times, say 1/2 inch from the muzzle, same machine rest. Almost certainly these sheets will be ragged by comparison.

Now you have two baselines of what paper looks like at two distances. Proceed to forgo the machine rest and shoot the gun normally with paper against the barrel. If the thought experiment works, sheets of paper in normal shooting are going to look more like either set “A” or set “B” and you’ll now have an idea of whether a specific gun recoils or not before the bullet leaves the barrel.

We do know that target rifles all recoil and continue to expel burning powder, so a level of fine discernment in what you are looking at would have to be employed. For paper that didn’t bow forward at bullet exit, from catching powder, the side opposite the muzzle will accumulate more residue. It is possible to avoid this “tainting” of results by devising something of small bent paper, that will fall off the barrel end if it recoils, but if it does not recoil, will be be witness marked by the bullet as it passes. But that is getting into areas that are going to invoke Darwin’s principles, and so I’ll shut up on that count, but it’s possible, in the enclosed facilities of trained professionals, by them, of course, inquire there or with Myth Busters if interested.

Sounds like substituting conjecture for actual experience.

 

[BoydAllen]

I have a great illustration of how a "magnum" and accuracy interrelate.

After several of us with 6 BRAs were blown off target at the 2018 NBRSA regionals, I decided to build a 300 WSM for LR BR. Several years earlier I had used a 300 WSM in 1K BR with good success.

Now the 300 WSM isn't really a magnum, but it does have double the case capacity of the 6 BRA.

So I built a 300 WSM 17 lb light gun. I did a good job on the chamber. My first 600 yd match with it I shot in a relay where a storm blew through. While I did shoot small group of the match, I didn't really get any useful info. Also, after the match when I went to remove the muzzle brake the whole barrel unscrewed. So my first BR "magnum" lesson was to torque the barrel to at least 60 ft lbs.

The second match was the real test. I shot first relay in an NBRSA 600 yd match. While I won the entire match for score, I was last in my relay for group. The reason was the 17 lb 300 WSM moved about three times as much under recoil vs a 17 lb 6 BRA and I just couldn't shoot it fast enough in good conditions to keep up with the 6s. In LR BR, to have good groups you must be able to shoot quickly to keep all your shots in the same condition.

So I concluded that the 300 WSM probably wasn't a good choice as a LG in 600 yd BR. Now Bill Johnson's 70 lb heavy gun in 300 WSM was very competitive at 600 yds. So I decided to stick with the 6 BRA for LG and build a 300 WSM HG.

My HG weighs 30.5 lbs. It recoils about as far back as the 6 BRAs, maybe a tiny bit more, but I can shoot it as fast as a 6 BRA LG. I have only shot it in IBS 1000 yd matches but it shoots well. Not as good as a 6 BRA when the conditions are good, but in average to poor conditions it seems to have an advantage. The 300s seem to score better than the 6s in most conditions.

A good illustration is the first match where I shot the 300 WSM HG. Both days I shot the second best group and score. Day one was a 4.33" 100-5x, and I think I was beat by a 300 SAUM IMP. The second day was outstanding conditions. I shot a 3.855" 100-3x, but was beat by a 6 BRA that shot a 2.695" 100-something X world record.

BTW, the smallest group and highest score ever shot in any 1000 yd competition was shot earlier this year with a 300 WSM. It was a 2.6 something 100-10x.

Pointing out something that you probably caught in the article that others may have overlooked, the fellow that shot that record did not like the way he gun was tracking with state of the art equipment so he changed things around to fix that. As you undoubtedly are well aware for more "normal" weight rifles heavier recoiling calibers cause more bag interface problems that can and often do result in shot to shot variations in how the rifle sits in the bags. His innovation addressed that issue directly, in a very outside the box manner. IMO others should take note...but as a rule shooters are slow to adopt new ideas.

 

[INTJ]

Pointing out something that you probably caught in the article that others may have overlooked, the fellow that shot that record did not like the way he gun was tracking with state of the art equipment so he changed things around to fix that. As you undoubtedly are well aware for more "normal" weight rifles heavier recoiling calibers cause more bag interface problems that can and often do result in shot to shot variations in how the rifle sits in the bags. His innovation addressed that issue directly, in a very outside the box manner. IMO others should take note...but as a rule shooters are slow to adopt new ideas.

I talked to him on the phone after he shot the record. I don't know why he had a hard time getting his LRB to track--most of have very good results with them. Regardless, like you mentioned, he kept at it until it tracked well for him.

My current heavy gun has a Richard's Microfit BR stock. (My solid fill LRB didn't arrive until after I had packed my milling machine.) I added an LRB rudder, rails on the fore end, and 5lbs weight in the butt. This stock, as ugly as it is, tracks very well. I did what I knew needed to be done to get it that way.

I just finished finding a load for my 33-28 Nosler. 250 grain Accubonds at 2825 fps. The rifle weighs 8 lbs 12 oz with its 4.5-14x scope. It generates almost 50 ft lbs of recoil (no brake). The best load is shooting about .6 MOA. I am happy with that as this is a "timber" gun not meant to be shot past 500 yds.

I hold it into my shoulder, push forward against the rest stop, and hold the fore end down on the front rest. It launches completely off the front rest each shot. I do wonder if I put a brake on it if it would shoot tighter due to less recoil.

 

[davidjoe]

Lots of posts, not enough time...

Had not seen this explanation yet, so:

Recoil starts at ignition. Equal/opposite stuff. The next bit is key in my mind. As the pressure builds and gas expands, the pressure vessel grows as the bullet travels forward. As a pressure vessel applies a uniform amount of force in all directions, the center of the vessel must travel forward to remain central of the vessel. Equal/Opposite forces and resistance come into play here as the rifle and bullet both resist the movement of the center of pressure. The 22lb rifle versus the .0307lb (215 Berger) have very different amounts of resistance. The bullet also has the aid of rifling friction, which can be treated as negligible, so long as the bullet escapes.

To the OPs other question about an infinitely long barrel, the rifling will eventually slow the bullet back to stationary, as will the vacuum created by a negative pressure as the gas expansion ceases and the bullet temporarily remains in motion. The slowing of the bullet will act as a brake to end the recoil but will not return the rifle to its initial position, because the bullet & powder/gas are no longer in the same position as before charge was lit. In this hypothetical scenario, the center of mass (assuming a perfectly linear recoil) should remain the same, because of the closed system principle.

This would be the same as if you were in a cargo van and pushed off a seat back to propel yourself to the rear before hitting the back doors. The van would move to account for the change in center of mass. Another way to think about the shift in center of mass is with the closed system of a person on a motorcycle. While balanced and stationary, the rider can thrust their body to push/pull the bike a small amount. The motion of the system on a flat surface is a direct correlation to the change in center of mass.

I hope there was some value somewhere in there...

This phenomenon is actually what spurred my post. I didn’t want to theorize or converse solely alone on the question of whether a center of gravity shift (or CM and especially as worded in your original post) is all that’s really, or possibly, going on in the rifle pre-exit.

Besides the firehose nozzle, there are a couple of visualization analogies that bother me, fairly relentlessly. I’d be the first to admit that if we put a grandfather clock on a platform over ball bearings, the motion of the pendulum is going to ever so slightly move the clock in counter step to its swing, until that brings it to a premature stoppage, and that slight side to side displacement is not what I’d call self-propulsion, but simply finding COG.

Second, is the powerful image of an Olympic hammer thrower. The moment of dramatic “disconnection” between the person and the weight is when the rotating person now recoils in the opposite direction of the hammer, very violently to a near fall. All the energy is contained in that system until disconnection. If he never let go, and just slowed down back to a stop, is that not like a bullet that never exited, I wonder.

A system finding its COG is a really “mild” process. I don’t think it’s even speed dependent; - if you used your finger to manually move the pendulum of the grandfather clock on ball bearings 5 inches to one side, spread over an hour’s time, I think the clock would end up in the exact same place at swing’s max, even though the pendulum’s hour long swing developed infinitesimally low momentum. Absent ball bearings, it’s not even close to wanting to move on its own. I alluded way up top to whether this fixed and limited amount of work is all that’s being done pre-exit. I still wonder that. If COG dislocation is not a function of momentum, then it’s not affected by how fast or slowly the bullet and gasses move from one end of the barrel to the other, and in pre-exit recoil terms, a magnum’s higher velocity would not change anything. (?)

I hear you on pre-exit velocity affecting pre-exit recoil. But while the bullet is still inside the barrel, probably pulling very hard forward on it, how is that not like throttling up on a model jet engine contained on a stand inside a steel cargo container? Whether we give it half or max fuel, the container is still absorbing and negating all its thrust. But at the same time there is no question that if instead of a bullet in front of the charge, there was an immobile rod, the rifle would go backward on firing. A rifle prevented from recoil should chrono a bullet faster than one that is recoiling while the bullet is still in it. I wonder if there is data on this. I don’t personally see it shooting LR Fclass, though.

If I visualize a pressure bubble of heated air in the middle of a balloon, (relevant because nothing escapes) I certainly agree that it seeks center and all sides try to move away from it.

On the other hand if pre-exit recoil is really a net of nothing more than COG dislocation, (and I’m not saying it is but have sure wondered about that because it’s a closed system until exit), and if COG adjustment to dislocation is not even a function of momentum, as the grandfather clock pendulum manually raised would indicate, then it, all by itself, truly is a very mild force, right? One that in many types of rifles would not overcome the inertia of the rifle sufficient to move, pre-exit, I’m thinking. That’s of course if those “ifs” are true.

 

[Firemedic301]

Would a rifle with an infinitely long barrel where nothing escaped from it recoil when shot? Let’s say the air is removed from the barrel in front of the bullet, first.

I don’t know the answer to this, but to me the analogy would be me standing on a flat bed trailer, pushing a lawn tractor from one end to the other. Does my pushing against the flat bed to move the tractor forward have any effect on the tendency of the flat bed to move either forward or backward.

Sounds like the makings of a COOL MYTH BUSTERS episode?

 

[Mr. Ten-X]

Yep...and Mid Tompkins winning at Perry with a 300 Winchester Magnum in the 60s

Amazing how many prone/sling shooters are winning with them now, eh?

 

[gcabrera]

This phenomenon is actually what spurred my post. I didn’t want to theorize or converse solely alone on the question of whether a center of gravity shift (or CM and especially as worded in your original post) is all that’s really, or possibly, going on in the rifle pre-exit.

Besides the firehose nozzle, there are a couple of visualization analogies that bother me, fairly relentlessly. I’d be the first to admit that if we put a grandfather clock on a platform over ball bearings, the motion of the pendulum is going to ever so slightly move the clock in counter step to its swing, until that brings it to a premature stoppage, and that slight side to side displacement is not what I’d call self-propulsion, but simply finding COG.

Second, is the powerful image of an Olympic hammer thrower. The moment of dramatic “disconnection” between the person and the weight is when the rotating person now recoils in the opposite direction of the hammer, very violently to a near fall. All the energy is contained in that system until disconnection. If he never let go, and just slowed down back to a stop, is that not like a bullet that never exited, I wonder.

A system finding its COG is a really “mild” process. I don’t think it’s even speed dependent; - if you used your finger to manually move the pendulum of the grandfather clock on ball bearings 5 inches to one side, spread over an hour’s time, I think the clock would end up in the exact same place at swing’s max, even though the pendulum’s hour long swing developed infinitesimally low momentum. Absent ball bearings, it’s not even close to wanting to move on its own. I alluded way up top to whether this fixed and limited amount of work is all that’s being done pre-exit. I still wonder that. If COG dislocation is not a function of momentum, then it’s not affected by how fast or slowly the bullet and gasses move from one end of the barrel to the other, and in pre-exit recoil terms, a magnum’s higher velocity would not change anything. (?)

I hear you on pre-exit velocity affecting pre-exit recoil. But while the bullet is still inside the barrel, probably pulling very hard forward on it, how is that not like throttling up on a model jet engine contained on a stand inside a steel cargo container? Whether we give it half or max fuel, the container is still absorbing and negating all its thrust. But at the same time there is no question that if instead of a bullet in front of the charge, there was an immobile rod, the rifle would go backward on firing. A rifle prevented from recoil should chrono a bullet faster than one that is recoiling while the bullet is still in it. I wonder if there is data on this. I don’t personally see it shooting LR Fclass, though.

If I visualize a pressure bubble of heated air in the middle of a balloon, (relevant because nothing escapes) I certainly agree that it seeks center and all sides try to move away from it.

On the other hand if pre-exit recoil is really a net of nothing more than COG dislocation, (and I’m not saying it is but have sure wondered about that because it’s a closed system until exit), and if COG adjustment to dislocation is not even a function of momentum, as the grandfather clock pendulum manually raised would indicate, then it, all by itself, truly is a very mild force, right? One that in many types of rifles would not overcome the inertia of the rifle sufficient to move, pre-exit, I’m thinking. That’s of course if those “ifs” are true.

This mental exercise may help.
Imagine we are using a normal size rifle made out of a very light but strong metal, that weighs only 100 grains. Additionally we are shooting with it a bullet made out of a very dense metal, a very short 6mm bullet that weighs 15 lbs.
Using a point on the bench as reference; if ignition happens at time t=0, then at time t=0+ (an infinitesimal time later) which of the two will move with respect to the point of reference on the bench; the heavy bullet or the light rifle?
I think the correct answer is both, but one faster (the very light rifle in this case) than the other (the very heavy bullet) following the relationship of conservation of momentum.

I may be missing something, as I cannot find the reason to ‘bias’ the rifle to stay stationary while allowing the bullet to start moving.

 

[BoydAllen]

Going back to experience, that is well known by many shooters. When considering the case of benchrest rifles shot free recoil on the usual rests/bags, it is well known that if a the rifle does not slide smoothly on the bags, if the bags are made sticky by humidity, or anything else, accuracy will suffer. You do not want it to hang up even a little. My question would be how could that be true if the rifle is not moving before the bullet leaves the barrel? Imaginings have made this much more difficult than it really is.

 

[davidjoe]

I don’t disagree with the intuitive and experiential aspect of the two above, but here’s a tougher “if so then why” question I’d return to both.

Given that a bullet starts slowing down the exact moment it leaves the barrel, one following conventional rationale could be forgiven for concluding rifle recoil sharply diminishes then.

But the opposite happens. When the rifle can no longer “push” against the bullet, and all the pressure is released, there’s actually a near vertical increase in recoil on the rifle’s recoil curve. What line of momentum conservation intuition explains this? The affect of delinking two objects seeking opposed directions, at least in that the bullet no longer pulling the barrel forward, isn’t something anyone seems to want to comment on, but if that’s not a part of recoil, why is the force evident at separation so clearly demonstrated in the other examples without controversy, I’ve mentioned, but not here applicable. Here’s one I’ll come back to, if an astronaut running out of oxygen drifts 10 feet from the hatch no matter what movements he makes, what do we expect he’ll be forced to do?

Regarding the light rifle and heavy bullet, - being the same as a regular rifle around an immovable rod, I’d say yes, like all sides of a balloon want to move away from air pressure, that is the tendency, but where one side is heavily biased and there’s only a finite time for inertia to be overcome before the bullet is gone, what we are really inquiring is whether that happens any differently with magnum loads, if even at all, in some guns.

For illustration, pressure to motion is not a linear function, and this is my problem with talking about primer ignition as material starting point. If it takes me 1 second to go from just neutrally gripping the bar on a bench press, to passing every pound of upward pressure until I exceed the plates’ weight and it departs the bench stand, it doesn’t really matter that I pushed upward with 200 pounds at .8 seconds, or that something fleetingly lightened or added to the load, so long as I haven’t yet hit the threshold to raise it anyway; it’s not moving up at all until more than 225 is exceeded, and it certainly doesn’t matter if I push upward with 80 pounds for 15 seconds, no work is done, there is no 1/3 of the lift, it will not move at all.

I’m thinking that the non-nozzle element of recoil - momentum opposite the bullet may, be beneath the movement threshold (intertial) of most firearms explaining why video so often doesn’t show pre-exit movement. It’s like casually grasping a weight as merely a spotter. The nozzle-propulsion portion seems sufficient to force back most every rifle, but of course the bullet is already gone and cannot be affected by that particular disturbance to the gun, and actually the moving blockage is what let the pressure build enough to have that nozzle effect. There is likely some combination to every target rifle and load where it can’t move any distance, before the bullet is gone, regardless of which is the correct mechanism and material starting point of recoil.

It’s extremely hard to push a mid-barrel jacketed, lodged bullet either direction to clear a primer-fire-only jam. I believe a bullet being pushed at firing, causes the barrel to exert a very strong forward pull away from the receiver, especially as the bullet gets going. In that regard I still don’t know whether moving two+ feet forward pre-exit amounts in the net of things, to close to just a shift in center of mass of the rifle. I’m cognizant that the formula for measuring the increasing momentum/velocity to the point of the barrel’s end in KE, is the accepted result for momentum imparted to the rest of the rifle in the opposite direction, but I remain perplexed how, as far as that calculation is concerned, it doesn’t apparently matter that one projectile of a given weight may tightly fit the barrel and pull the rifle forward, while a loose fitting ball or slightly longer narrower bullet of the same weight that easily traverses the barrel, will by formula be required to have netted exactly the same push back on the rifle as a function of only two things, weight and velocity.

I am familiar with wasted energy being spent as a concept and a reality, and that varying forward barrel pull is probably already baked in and just manifests as offsetting greater pressure in all directions, but here it would seem that there is a loose end as everyone agrees that bullet friction pulls an unlimited barrel forward, or the same thing, eventually stops a freely recoiling barrel, necessary to distinguish its result from the jet effect of regular barrel that would keep going until something stops it, but what will have the equivalent decelerating effect of friction with a bullet less capable of friction, or an aerated projectile, such as ice, that never exited, to maintain the distinction.

… This last example reminds me of the enclosed system of a small jet mounted in a shipping container where the exhaust can have no recoiling/propulsive effect on the sealed container as a whole, which re-raises the doubt in my mind as to whether a long/capped barrel that does not permit the bullet or anything else to exit, would recoil upon firing. This of course, is potentially important if it establishes a first, second, third order to known phenomenon, that are both difficult to observe, and possibly attributable to alternative causes.

 

[sdean]

Going back to experience, that is well known by many shooters. When considering the case of benchrest rifles shot free recoil on the usual rests/bags, it is well known that if a the rifle does not slide smoothly on the bags, if the bags are made sticky by humidity, or anything else, accuracy will suffer. You do not want it to hang up even a little. My question would be how could that be true if the rifle is not moving before the bullet leaves the barrel? Imaginings have made this much more difficult than it really is.

^^^^^^^
This. The “why” won’t make any difference. I spend as little time as possible thinking about something I can’t do anything to change it.