How Much Can 9mm Bullet Weight Affect POI (S&W 3913)

[PolarFBear]

IWestatbus:

The 3913 is my favorite fire arm. It was also my first firearm. But, I never could shoot it well. It always shot a little low and a little left. Without adjustable sights (yes I did try drifting the rear sight), I just learned to compensate. Those sights look fuzzy to me as well. As a check, I gave this pistol to my son who also experiences the same sight picture. Perhaps they just don't fit some eyes. Still, I like them. Have 3 of this generation and will buy another when seen. As for a CCW, I have moved on to a Glock 19. Not in love with it but it WORKS.

 

[random guy]

Fire the same loads from a rest at 25 and 50 yards. At those ranges the difference will show up a lot more.

Well, that's what I thought, that the difference would increase proportionally with range but from what I can tell from my small and sloppy sample (I cannot explain the low flyers in both groups) there is virtually no elevation change to proportionally increase. At least nothing like we are used to seeing in revolvers. 4 X 0 is still zero. 4 X 1/2" would only be 2" at 50 yards. Not much.

I mean this is like comparing 300 gr cast softball .44 mag to sizzling 200 gr max loads. Just about the most extreme ends of the scale. I did not expect this result. Granted, tighter groups (better loads and shooter) would make this more definitive. Another factor may be the simple difference in total recoil between magnum revolvers and a 9mm. It's not like the 9 just lays there though. This really has me wondering.

 

[JohnKSa]

Are you a good enough shot to separate two groups that are a half inch apart or would it look like one group at 25 or 50 yards?

Fire the same loads from a rest at 25 and 50 yards. At those ranges the difference will show up a lot more.

I submit that if it is necessary to shoot groups, from a rest, and at distances that are 2 to 4 times further than typical handgun ranges, to even see a difference, that it is perfectly accurate to say: "There's very little recoil arc in a locked breech semi-auto while the bullet is in the bore." or to say: "That is because there's very little muzzle rise while the bullet is in the bore."

Just to be clear, I didn't claim that there's NO difference at all in POI due to bullet weight difference. Here's my first response to the OPs question.

The muzzle doesn't really begin to rise significantly until the barrel unlocks and, by design, that takes place after the bullet leaves the bore. As such, there's not as much effect on point of impact when changing bullet weights.

 

[Walt Sherrill]

Well, that's what I thought, that the difference would increase proportionally with range but from what I can tell from my small and sloppy sample (I cannot explain the low flyers in both groups) there is virtually no elevation change to proportionally increase. At least nothing like we are used to seeing in revolvers. 4 X 0 is still zero. 4 X 1/2" would only be 2" at 50 yards. Not much.

Something has changed, and I can't post from Photobucket as I used to. I can, presently, only show the targets in question as an attachment. Click on the "attached Images" link at the bottom. I have posted other images here recently, using the [ IMG ] function, but it wouldn't work this time out.

When I look at the target, I shudder, as my personal shooting performance was terrible. But, I was rigorous in doing everything the same. (The target says 50' but it was shot at 30'-35'.) A first shot that was not part of the test was shot off target so that the first TEST ROUND was chambered by the gun cycling, and not done manually.

I shot the first test round on the first target using a 115 gr round, then the second using a 124 gr. round, then the third using a 147 gr. round, and then came back and repeated the process until all 15 rounds were fired. The rounds were loaded in the mag to allow that. I used the same point of aim on each target, and sights were not adjusted. (My eyesight has been adjusted since then, via cataract surgery... That might make a difference if I try it again.)

I don't know why the 147 gr. rounds made bigger holes in the paper, but they did.

... Another factor may be the simple difference in total recoil between magnum revolvers and a 9mm. It's not like the 9 just lays there though. This really has me wondering.

I'm not sure the total difference in recoil matters as much as it seems it should.

As I've noted in earlier replies, until the bullet has almost moved out of the barrel, there's not much connection between the slide and barrel and the frame, and until THAT connection becomes more direct and forceful, there's not much way for any recoil (heavy or light) to have an effect on the frame (and barrel rise.)

The relationship of the bullet, barrel and slide, until the bullet leaves, is based on a fixed, physical relationship, and faster, slower, heavier or lighter bullets don't change that fixed physical relationship. The only thing that changes is the speed with which it is all takes place. But when the bullet is moving as part of that relationship, the timing doesn't seem to matter much, either.

Some recoil force may pass to the frame more quickly if the bullet is moving faster, and to the frame more slowly if the bullet is going slower, but the bullet position is always relatively the same with regard to slide movement. I don't see how the barrel can rise differently from one load to the next, as slide and barrel movement is the main transfer agent!

When the bullet is gone and while the recoil spring is still being compressed, the momentum of the slide and barrel moving to the rear continues until they each hit their respective stops in the frame. THEN you really see (and feel) the force of recoil, and that when the force of all of that mass of material moving to the rear directly causes the gun in the hand to tilt upwards.

While weight shift and more recoil spring pressure is also affecting the gun prior to that, almost all of this movement takes place AFTER the bullet is gone.

 

[random guy]

I wouldn't have believed it if I hadn't seen it. If not a universal rule, it certainly appears to be an unusual tendency of this type of semi-auto pistol. And a good tendency...unless you want to adjust POI by load.

 

[random guy]

JohnKSa:

I've got three boxes of 9mm ammo, all from the same manufacturer and all with different bullet weights that are slated for a test like yours.

I'm going to add one wrinkle. In addition to shooting groups from all three weights to see if a POI difference can be seen, I'm going to fix the slide closed and fire the groups again with all three weights. Right now the test is on hold while I come up with a reliable and practical way to fix the slide closed without causing any damage to the pistol.

It would be very interesting to also try a 1911 (or similar) with the slide locked, as the theory is that their quicker barrel tilt is part or all of the reason that we see elevation change with bullet weight in them. At least I think we do. Been a while since I shot mine much.

Not sure how you keep the slide locked though.

 

[45_auto]

Some evidence would make your argument more convincing.

What evidence are you looking for? I'm not going to invest in a fixed rest and shoot thousands of rounds of ammo to provide you with statistically meaningful proof that 230 grain ammo shoots .010" higher at 25 yards than 200 grain ammo which shoots .010" higher than 185 grain ammo. Just doesn't mean that much to me.

And how is the extra force that accompanies a heavier, slower bullet transferred to the frame BEFORE the bullet exits the barrel?

As previously stated, the momentum in a 1911 is transferred to frame thus to the shooter primarily by the cocking of the hammer (this is why the small radius on the bottom of the firing pin stop is critical and makes such a large difference in felt recoil) and recoil spring BEFORE the bullet exits the barrel.

No one is disputing the fact that the distance the slide moves is fixed by the mechanics of the pistol. I'm having a hard time figuring out why you can't understand that a heavier bullet moving 10% slower will spend 10% more time in the barrel and thus will be more affected by the forces (minimal as they are) transferred to the shooter as described above.

 

[Walt Sherrill]

As previously stated, the momentum in a 1911 is transferred to frame thus to the shooter primarily by the cocking of the hammer (this is why the small radius on the bottom of the firing pin stop is critical and makes such a large difference in felt recoil) and recoil spring BEFORE the bullet exits the barrel.

We aren't really talking about how recoil is transferred to the shooter. We're talking about HOW recoil affects barrel rise while the bullet is still in the barrel. That is clearly dependent on the frame being affected by recoil. This is addressed more directly, below.

No one is disputing the fact that the distance the slide moves is fixed by the mechanics of the pistol. I'm having a hard time figuring out why you can't understand that a heavier bullet moving 10% slower will spend 10% more time in the barrel and thus will be more affected by the forces (minimal as they are) transferred to the shooter as described above.

If the slide movement is fixed by the mechanics of the pistol, why is there more recoil applied to the frame BEFORE the bullet leaves if the the relationship of the components are the same regardless of bullet weight or speed? It's all based on physical movement, isn't it? A fixed-barrel gun seems to behave differently than a Browning Short-Recoil Locked-Breech gun, even though the physical forces affecting their behavior are the same.

A number of us don't understand why you can't (or won't) offer at least some evidence, like targets with holes in them, that show that a heavier, slower bullet's extra time in the barrel makes a difference in a BROWNING SHOT-RECOIL LOCKED-BREECH (SRLB) semi auto. We all agree that bullet weight and bullet speed does affect barrel rise in a fixed-barrel gun. You offer us only a theoretical argument and no proof that physics affects the behavior of the Browning SRLB system in the same way it affects a fixed barrel gun.

A number of folks here have shown the results of their tests or talked about what they've observed.

• lwestatbus is for more experienced in statistical analysis than most of us, and he found no statistically significant differences between bullet weight groups in the test he did.
  
• I was finally able to post images of my targets -- and I certainly sure can't brag about MY accuracy. I was consistent! (I don't remember which gun I used. If I do it again, I'll use my most accurate 9mm.)
  
• Jim Watson could find no difference in the groups of his 200 gr. and 230 gr. bullets fired from his 1911. And that's MORE than a 10% difference in bullet weight. Jim did see a difference with 185 gr. bullets -- but JohnKsa offered an explanation for THAT difference that may have been caused by the barrel link. (My gun was linkless.)
  
• random guy, did as others have, and was surprised that he saw no differences in points of impact.

We've shown you ours, now you need to show us yours.

You don't need a Ransom Rest to offer evidence to prove your claims. You don't need to fire thousands of rounds. You just need the same sort of rest you'd use when sighting in a gun -- a sandbag or bag of beans or rice -- a target, a variety of bullet weights, and a slow, steady press on the trigger as each shot is fired. Firing all of the bullets from the same gun without changes to the sights, and using the same point of aim makes for an easy test. If you use three or four bullet weights -- maybe 5 or 10 rounds each --means you'd shoot less than one box of ammo.

If you push the target out far enough, I'm sure you'll should see some differences, and the farther you go, bullet velocity will play a more-noticeable role in the results -- as because bullets drop at the same rate whether they're heavy or light. That means given the same barrel alignment with a target, a lighter bullet moving faster will hit HIGHER at greater distances than a heavier bullet that moves more slowly -- the lighter bullet it will have gotten there sooner and have dropped less.

If all the components (bullet, barrel, slide, frame AND recoil spring compression) have the same physical position in relationship to each other whether the bullet is heavy and slow, or light and fast until the bullet leaves the barrel how does that (supposedly) extra force cause barrel rise when a heavier/slower bullet is fired transferred to the frame before the bullet leaves the gun?

Where does that extra force come from and how is it transferred to the frame? The only direct contact of the slide (prior to bullet exit) with the frame is through the recoil spring. A spring doesn't know that heavier recoil is at play -- it reacts by traveling a given distance when compressed by physical movement. If bullet movement in the barrel is a fixed relationship regardless of bullet weight or speed, the amount of spring compression will also be the same while the bullet is still in the barrel.

That seems to suggest that the force transferred to the frame by the physical movement of the slide will be the same, too, until the bullet is gone, regardless of bullet weight or speed. The time involved for all this to happen is different, but the amount of physical movement is not different. Once the bullet is gone, things change dramatically. The PHYSICAL MOVEMENT OF THE SLIDE and how the force of that movement is transferred to the frame is the critical factor.

You haven't shown us WHY or HOW heavier, slower bullets cause a Browning SRLB barrel to rise higher while the bullet is still in the barrel . You seem to acknowledge that the physical relationship of the components are unchanged by bullet weight or speed while the bullet is in the barrel -- that is, in effect, a fixed relationship. That suggests that the force transferred to the frame -- dependent on slide movement prior to the bullet's exit -- is also the same, regardless of bullet weight or speed.

You could easily offer us you own test results that show different points of impact on a target that vary with bullet weight or speed. Give us more than theory -- which is theory that may be misapplied in this case.

.

 

[ShootistPRS]

In a self defense situation the change in impact of a slower heavier bullet than that of a faster lighter bullet is insignificant. Whether it is being fired from a locked breach semi-auto or a 6" revolver makes no difference.

What I maintain is that there is a measurable amount of difference between the two regardless of the gun used. I practice shooting at 25 and 50 yards more often than I do at 7 yards and less. I rarely use any rest unless I am testing a load or a gun. Once I am familiar with a handgun the only time I practice at less than 25 yards is in "combat" or defensive training. I train at 25 yards shooting 6 inch falling plates. That is for speed training. I shoot the "El Presidente" at 7 yards with the targets 3 yards apart. I do that for speed training. I don't actually use the sights on those games, I fire instinctive point fire. At less than 7 yards I train to shoot from "the hip" without extending my arms and using one hand hold.

I can see the difference in impact points between heavier and lighter bullets when using my sights. I don't shoot small enough groups with instinctive shooting to tell the difference. You have to be capable of shooting groups to see the difference.

 

[mavracer]

We aren't really talking about how recoil is transferred to the shooter.

Ultimately yes you are because it get's to the shooter thru the frame.
One of the biggest reasons you see less difference in POI when changing bullet weights in a semi auto is bore axis above the pivot point (web of your hand).

And 45_auto is absolutely correct about the firing pin retainer and it's radius being an important factor.

 

[ShootistPRS]

In a locked breech semi-auto the barrel and slide are never in "free recoil". They push on a spring that rests against the frame. That push is recoil that is felt by the shooter. Placing the gun lower in your hand (gripping the gun higher) will help to reduce the amount of angular displacement but it does not negate it until the barrel is in-line with the center of your wrist.

As soon as the link or ramp begins to move the rear of the barrel down the angle of the barrel rises. Even though the barrel is not completely disengaged it is moving vertically. The entire time that the barrel and slide are moving the recoil is being absorbed by your hand. (as transfered through the recoil spring to the frame). Recoil always begins when the bullet starts to move.

 

[Walt Sherrill]

In a locked breech semi-auto the barrel and slide are never in "free recoil". They push on a spring that rests against the frame. That push is recoil that is felt by the shooter. Placing the gun lower in your hand (gripping the gun higher) will help to reduce the amount of angular displacement but it does not negate it until the barrel is in-line with the center of your wrist.

As soon as the link or ramp begins to move the rear of the barrel down the angle of the barrel rises. Even though the barrel is not completely disengaged it is moving vertically. The entire time that the barrel and slide are moving the recoil is being absorbed by your hand. (as transfered through the recoil spring to the frame). Recoil always begins when the bullet starts to move.
ShootistPRS is online now Report Post

Do you agree that the key relationship of the components -- barrel, slide, frame, bullet, and recoil spring are all fixed in their relationship (i.e., how they move with regard to each other) until the bullet leaves the barrel?

IF not, tell us what changes in those relationships due to different bullet weights or speeds.

IF they are fixed, the amount that the recoil spring is compressed when the slide and barrel have move that trivial 1/10th of an inch and the bullet leaves -- and the amount of forces pressed to the frame -- is the same regardless of bullet weight or speed. If they aren't the same, tell us why they're not the same. We're talking about the physical relationships and slide travel, not the TIME involved.

Nobody has claimed that the recoil has no effect in a Browning Short-Recoil Locked-Breech gun. The claim is that its effect is no different with heavier/slower bullets than with faster/lighter bullet UNTIL after the bullet is out of the barrel.

Recoil's transfer to the frame is based on slide movement. And even if it's being passed faster or slower, the slide is moving the same amount until the bullet is gone. The total recoil effect on the frame is the same -- until later.

If the slide moves the same distance to the rear, regardless of bullet weight or speed --and slide movement is what transfer recoil to the frame -- what other force is at play that causes the barrel and slide to rise when a heavier and slower load is used that isn't caused by slide movement down the frame?

 

[Walt Sherrill]

Ultimately yes you are because it get's to the shooter thru the frame.
One of the biggest reasons you see less difference in POI when changing bullet weights in a semi auto is bore axis above the pivot point (web of your hand).

And 45_auto is absolutely correct about the firing pin retainer and it's radius being an important factor.

Ultimately we're talking about how recoil affects barrel rise -- and why it might rise MORE BEFORE the bullet has left the barrel when the bullet is heavier/slower, or lighter/faster.

With a 1911, the firing pin retaining plate and its radius at the rear of the frame has moved only 1/10th of an inch to the rea when the front of the slide has move that same 1/10th of an inch. That is force applied to the frame, to be sure, but like the recoil spring, the same amount of slide travel occurs regardless of bullet weight or bullet speed. As noted in other responses, the distance the bullet, slide, barrel, frame and recoil spring move is a fixed relationship.

We can add the hammer-spring and hammer to the discussion, but it still doesn't change anything. If we switch to a striker-fired gun, it won't change anything, either. Ditto a linkless Browning SRLB design.

SLIDE movement (the distance traveled) when the bullet leaves the barrel is the key factor, and it's the same, regardless of bullet weight or speed. How fast all of this happens is different, but not how far things move.

As I noted in an earlier response, nobody is claiming that recoil isn't a factor with the Browning SRLB. What some of us are claiming is that with Brownging SRLB design, a light/fast bullet and a slow/heavy bullet the moves the same amount until about the bullet is gone. THEN, things change.

What would cause the slide/barrel to rise more, given the same (FIXED) amount of slide travel when a heavier, slower bullet is used than when a faster/lighter bullet is used? I've been led to believe that the bullet always leaves the barrel at the same point of slide travel. Is that not right?

 

[ShootistPRS]

Do you agree that the key relationship of the components -- barrel, slide, frame, bullet, and recoil spring are all fixed in their relationship (i.e., how they move with regard to each other) until the bullet leaves the barrel?

IF not, tell us what changes in those relationships due to different bullet weights or speeds.

IF they are fixed, the amount that the recoil spring is compressed when the slide and barrel have move that trivial 1/10th of an inch and the bullet leaves -- and the amount of forces pressed to the frame -- is the same regardless of bullet weight or speed. If they aren't the same, tell us why they're not the same. We're talking about the physical relationships and slide travel, not the TIME involved.

Nobody has claimed that the recoil has no effect in a Browning Short-Recoil Locked-Breech gun. The claim is that its effect is no different with heavier/slower bullets than with faster/lighter bullet UNTIL after the bullet is out of the barrel.

Recoil's transfer to the frame is based on slide movement. And even if it's being passed faster or slower, the slide is moving the same amount until the bullet is gone. The total recoil effect on the frame is the same -- until later.

If the slide moves the same distance to the rear, regardless of bullet weight or speed --and slide movement is what transfer recoil to the frame -- what other force is at play that causes the barrel and slide to rise when a heavier and slower load is used that isn't caused by slide movement down the frame?

Once the trigger is pulled and the cartridge ignites there is no fixed relationship. The bullet is moving in the barrel, barrel moves (slightly) in relation to the slide and both the barrel and the slide move in relation to the frame under the recoil of the bullet and the spring is being compressed. It is, in fact a very dynamic relationship.

A heavier bullet has more mass so it imparts more movement to the parts of the gun and does so for a longer (slightly) time. (barrel time)

Clear your semi-auto and move the slide a tenth of an inch to the rear. While holding it there check the amount of vertical play in your barrel. (at both the muzzle and the breech)

After the bullet leaves the barrel it no longer has any effect on the gun at all. All the motion is imparted to the gun while the bullet is traveling down the bore.

The speed of the slides rearward movement is due to the velocity and mass of the bullet. (momentum conservation) The more momentum the bullet has, the more the slide moves in a given time.

The distance the slide moves before disengaging from the barrel is always close to the same but the time it takes to get there changes with the amount of momentum exchanged with the bullet.

The question you need to answer is, "At what point does the barrel (its locking lugs) begin to move downward away from the slide?" You will find that it is less than the time the bullet is in the barrel. You continue to bring up that the distance is the same but forget the the time is different. The time is determined by the weight and velocity of the bullet.
A car going 200 miles at 50 mph will be on the road 4 hours to get there but if you go 100 miles per hour you are on the same road for only 2 hours. The faster bullet gets out of the barrel faster and has less effect than the heavier slower bullet. The distance remains the same but the time changes.

 

[Walt Sherrill]

The question you need to answer is, "At what point does the barrel (its locking lugs) begin to move downward away from the slide?" You will find that it is less than the time the bullet is in the barrel. You continue to bring up that the distance is the same but forget the the time is different. The time is determined by the weight and velocity of the bullet.

Does the barrel of a Browning Short Recoil Locked Breech (SRLB) weapon unlock at a different point in the bullet's travel in the barrel when you use use a heavy bullet (moving slowly) than when you use a light bullet (moving more quickly)?

If it doesn't, what else can cause the barrel and slide rise when using a heavier/slower bullet before the bullet leaves the barrel which is before the slide has traveled 1/10th of an inch. Is there some way for recoil force to be transferred to the frame rather than through slide movement?

It would seem that if the bullet is moving more slowly, the barrel rise would also be happening more slowly. WHY is such a small amount of rearward movement causing what seems to be a disproportionate amount of barrel rise?

What would happen if two different loads, one with a heavy bullet and one a lighter one, both send their bullets down the barrel at the same velocity. How does the gun behave differently, then?

I've always understood that the process that leads to the bullet leaving the barrel in a Browning SRLB gun is a fixed one. While the time required for the bullet to move down the barrel can be different, the distance it travels and how the bullet physically relates to the other affected components (barrel, slide, frame, compressing springs) are all part of a fixed relationship based on bullet and barrel/slide movement. Barrel and slide movement seem to be the only way that recoil forces can be transferred to the frame.

If the barrel does unlock differently for a heavy/slow bullet than for a fast/light one, please explain why that is so. If it doesn't unlock differently (which means there can be no different barrel rise due to the barrel unlocking), what else is causing barrel rise before the bullet has left the barrel? Do you feel that the physical movement of all of the key components are NOT part of a fixed relationship until the bullet is gone? I agree that the time it takes for the firing cycle to complete itself will be different depending on the load and how fast the slide moves, but I continue to argue that the way the components move with regard to each other doesn't change when the do it more or less quickly..

Said in a different way, the speed of the process isn't the controlling factor -- instead it's the LOCATION of the different components, which are part of a fixed, predictable relationship. Nothing about that series of physical relationships changes when things are speeded up or slowed down. The components all move in the same way and travel the same distances -- they just do it at different speeds when the loads used are different.

Does any want to say that lighter/faster bullets leave at some point before the barrel unlocks while heavier/slower bullets leave after barrel/slide separation has begun. Is that the explanation for barrel rise? I have been led to believe recoil force being applied to the frame (as is the case with a fixed-barrel gun) is what causes muzzle rise.

High speed videos of Browning SRLB guns being fired show the bullet leaving the barrel after the slide and barrel have moved a small fraction of an inch. The barrel remains level and the bullet exits horizontally. The bullet path and the slide/barrel movement seem the same regardless of bullet weight, caliber, barrel length, etc. The very high-speed videos (73,000 frames per second) show no muzzle rise until AFTER the bullet is gone and the slide has moved farther to the rear. This can clearly be seen in the links in earlier messages.

IF slide movement is the way recoil force is transferred to the frame, and all bullet weights and bullet speeds cause the same amount of slide movement UNTIL THE BULLET HAS LEFT THE BARREL, it would seem that recoil isn't playing a big role in barrel rise when it matters -- while the bullet is still in the barrel.

 

[JohnKSa]

In a locked breech semi-auto the barrel and slide are never in "free recoil". They push on a spring that rests against the frame. That push is recoil that is felt by the shooter. Placing the gun lower in your hand (gripping the gun higher) will help to reduce the amount of angular displacement but it does not negate it until the barrel is in-line with the center of your wrist.

As soon as the link or ramp begins to move the rear of the barrel down the angle of the barrel rises. Even though the barrel is not completely disengaged it is moving vertically. The entire time that the barrel and slide are moving the recoil is being absorbed by your hand. (as transfered through the recoil spring to the frame). Recoil always begins when the bullet starts to move.

You've posted this more than once and I've already responded to it.

Rather than repeating it again, please consider the sightline vs. boreline diagram posted earlier and explain how significant muzzle rise while the bullet is in the bore could take place given what the diagram shows.

 

[mavracer]

The very high-speed videos (73,000 frames per second) show no muzzle rise until AFTER the bullet is gone and the slide has moved farther to the rear.

Look again closely, keeping in mind that with a 5" barrel every .005 is nearly an inch (.9 to be exact) at 25 yards.

Let's look at your theory in reverse. Once the bullet leaves the barrel it has no more input on recoil, the gun has already reached it's maximum recoil velocity if it weren't already starting to rise it never would

 

[Walt Sherrill]

Rather than repeating it again, please consider the sightline vs. boreline diagram posted earlier and explain how significant muzzle rise while the bullet is in the bore could take place given what the diagram shows.

I suspect the boreline and sightlines for most handguns are set by the gun makers for bullet impact at 20 yards. That distance also seems to be the sweet spot used in most of the ballistic tables cited by ammo makers. I've never noticed that much difference in bullet impact points at shorter distances regardless of bullet weight or speed. My tests at much closer distances didn't show any.

Bullets that must go farther would force sight adjustments -- which changes the boreline/sightline relationship. But what we see there, arguably, is the effect of the bullet's travel over time -- gravity is constant, regardless of bullet weight. That means that a slower bullet will drop more at a given distance than a faster bullet, and you've got to adjust your point of aim to compensate for that time-related variable.

As soon as the link or ramp begins to move the rear of the barrel down the angle of the barrel rises. Even though the barrel is not completely disengaged it is moving vertically. The entire time that the barrel and slide are moving the recoil is being absorbed by your hand. (as transfered through the recoil spring to the frame). Recoil always begins when the bullet starts to move.

I guess I'm beating a dead horse, but...

You seem to be saying that a heavier/slower bullet causes a different amount of vertical movement of the barrel than a lighter/faster bullet. What causes that to happen?

As far as I can tell, the movement of the bullet, barrel and slide on the frame remain n a FIXED RELATIONSHIP until the bullet is gone and the barrel and slide are fully unlocked. The speed with which these components move can change, but not HOW they move with regard to each other.

I think that for the barrel to unlock VERTICALLY in a different way when a heavier/slower bullet is used would mean the heavier bullet has traveled farther down the barrel during the firing cycle than a faster/lighter bullet would have traveled. That seems counter-intuitive. That says there is NOT a fixed relationship between the key components prior to the bullet exit from the barrel. Is that what you believe?

.

 

[45_auto]

You don't need a Ransom Rest to offer evidence to prove your claims. You don't need to fire thousands of rounds. You just need the same sort of rest you'd use when sighting in a gun -- a sandbag or bag of beans or rice -- a target, a variety of bullet weights, and a slow, steady press on the trigger as each shot is fired. Firing all of the bullets from the same gun without changes to the sights, and using the same point of aim makes for an easy test. If you use three or four bullet weights -- maybe 5 or 10 rounds each --means you'd shoot less than one box of ammo.

You must be joking. How close do you think you can locate the actual center of your population from 5 or 10 rounds?

Where is the population center based on this sample of five shots? Is it the center of the five holes, or do those 5 holes just happen to be above or below or to one side of the true center of the population? The more shots you fire, the more accurately you can determine that center.

How much difference are you expecting?

Let's say the difference is .25" at 25 yards.

Let's also say your pistol/shooter combination is good for 2.5" groups at 25 yards.

A quick estimation of how many shots you would need to locate the group center within a given error at a 95% confidence level can be approximated by 1/B^^2, where B is the error bound. Quick explanation here:

The sample size is an important feature of any empirical study in which the goal is to make inferences about a population from a sample.

https://en.wikipedia.org/wiki/Sample_size_determination

If we want to locate your group center within plus or minus .25", which is 10% of the 2.5" group you are shooting, you would need 1/(.10)^^2 = 1/.01 = 100 shots.

So if the bullet weight caused a .25" difference, and 100 shots only allows you to locate your group within plus or minus .25", that means that given 200 shots (100 shots of each bullet weight) you can't tell any meaningful difference between them.

If you want to locate the center within .10", which is 4% of your 2.5" group, then it will take 1/(.04)^^2 = 1/.0016 = 625 shots per group.

At that resolution of .10" on group center, even if your upper group center was off .10" inch low, and your lower group center was off .10" high, you would still have .050" between the centers of your groups if there was a .25" difference, and it will only take 1,250 shots.

You must have some BIG boxes of ammo to do it in less than a box!

I'll take another shot at simplifying the physics later if I get a chance.

 

[Walt Sherrill]

I'll take another shot at simplifying the physics later if I get a chance.

I wish you WOULD simplify the physics. But you may have to do some other explaining, as well.

Re: your graphic. It shows us that it's VERY POSSIBLE to misinterpret results, but I'm not sure it's a meaningful proof for this discussion. Another participant here who teaches statistics and analysis seemed to have no problem coming to a conclusion about bullet rise vs bullet weight using far fewer rounds. Maybe he needs to re-examine his findings and how he teaches statistical analysis to his students?

And there was a general consistency in the results cited by others who did their own tests. I showed an image of my results. Did we all make the same errors? Or were we simply shooting our handguns at targets so close that the differences aren't significant?

My assumptions:

• How far the bullet moves in the barrel is related and proportional to how far the slide and barrel move and how far a recoil spring or hammer springs are compressed.
  
• The components listed above act as part of a fixed relationship until the bullet leaves the barrel -- when the barrel and slide go to their different stops on the frame.
  
• Different weight bullets moving at different speeds will change the time it takes for the different components of this fixed relationship to go through their related motions, but not how the parts move in their relationships to each other.
  

This basic set of assumptions seem to be confirmed by the comments of many people considered experts on the subject. As I interpret them, these assumptions also seem to be confirm by observations, by simple tests (at least one of which was analyzed by a person familiar with statistical practices), and by high-speed vidoes. It appears that barrel tilt is the same UNTIL AFTER the bullet leaves the barrel. The point is that a very, very minor amount of barrel rise can have a big impact farther down range. Perhaps so, but farther down range many other factors can also affect bullet placement -- not the least of them being gravity. Can it have a large effect at typical handgun (self-defense) ranges?

It seems to be generally accepted that a .45, bullet exits the barrel before the barrel and slide have moved a bit less than 1/10th of an inch. In the 1911s I've owned, it always seemed that the barrel had to move a bit more than that before the link began to pull the barrel down. But that's hard to measure or verify if your not a gun builder or gunsmith.

But, even IF the link can come into play before the barrel has traveled that far, even before the bullet leaves the barrel, I would expect the link to pull the barrel down the same way/distance regardless of bullet weight or bullet speed -- because the link's action is dependent on slide/barrel movement with regard to the frame (to which the bottom of the link is attached). It's not about slide or bullet speed, but about the physical slide movement, and what I consider a FIXED relationship between the various parts as they move.

For a heavier/slower bullet to cause more barrel rise, it would seem to mean that the supposedly FIXED relationship of barrel/slide, bullet, and frame has to become become one that isn't fixed. It would seem to mean that the heavier/slower bullet has traveled less far when the the barrel begins to unlock from the slide than would be case with a lighter/faster bullet.

ShootistPRS mentioned different bullet momentum due to a heavier bullet, and also said that recoil was transferred in a subtly different manner when the barrel unlocks as a heavier/slower bullets is used.

I don't see how either one of those really apply, but maybe they do. I don't claim to be a good student of physics. That may be where you need to simplify the physics for me and others.

If any part of my assumptions above are wrong, show me why -- correct my misunderstandings about Browning SRLB function -- and we'll go from there.

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