Walt Sherrill
New member
Recently we had a long discussion about the effect of different bullet weights on recoil -- and whether heavier bullets (as I and others claimed) tended to hit higher on the target than lighter ones.
My claim was that because the heavier bullet was moving slower, the barrel rose a bit before the bullet was fully out of the barrel, and that raised the point of impact. That seemed intuitively obvious to me and to others, here.
JohnKSa and other said, "no, that isn't so". It appears I was wrong and he/they were right.
Well, I'm here with some convincing evidence supporting their position. I've found a number of super-slow motion videos of semi-autos in action, and it seems to confirm their point. If you think I'm waffling when I say "seem" or "seems" rather than saying "it proves they're right," my choice of words is based on observations that could be in error, but I don't think that's the case. The following videos seem pretty convincing to me.
As I was looking at the following videos I also looked at revolvers -- and the claim that recoil tended to be a bit different there, too. I have found nothing to suggest that revolvers are really all that different. I can understand why they MIGHT be different, but it seems that MOST of the difference may come into play AFTER the bullet has left the barrel. That's a different topic, and we can ignore it for the moment -- and I'll address it again, at the end, below the "-----------------".
When looking at Semi-Autos, here's what I found:
In semi-autos the slide and barrel move together to the rear as the bullet goes down the barrel. That was the earlier claim.
The only motion visible in the ultra high-speed videos is of the slide and barrel slightly moving to the rear until AFTER the bullet has exited the barrel. The slide and barrel don't start to rise UP gas is coming out of the barrel, and the barrel and slide has gone more to the rear, and started to separate. At THAT POINT the bullet is already gone.
Before the bullet exits the barrel, some of the rearward movement of the slide is likely transferred to the recoil spring and to the frame - but even that small amount of energy is a transfer of force that is primarily to the rear, and it has no up or down effect.
If the barrel doesn't rise until AFTER the bullet leaves the barrel, bullet weight or bullet speed down the barrel isn't affecting the barrel or slide's vertical position. That kills my earlier claim.
Bullet weight does affects bullet performance after it leaves the gun. But, a light bullet fired from a gun and a heavy bullet fired from a similar gun will both hit the ground at the same time if they're both fired from the same height and level, and exactly at the same time.
But if the light bullet is moving faster, it will hit a closer target more quickly than a heavier bullet (because gravity hasn't been working on it as long), and that lighter bullet should hit higher than a heavier bullet because it hits the target more quickly and has less time to be affected by gravity.
The point overlooked in this comparison, however, is whether the two rounds are loaded to be delivered at the same velocity. If the velocity is the same, they'll both get there at the same time. Felt recoil might not be the same, but felt recoil won't have any real effect until the bullet is out of the barrel...
Here are several videos that seem to offer proof:
The first one is of a 1911, and if you click the stop/go button on the bottom left of the video, you can stop the motion. If you do it just right, you'll see that the bullet leaves the barrel BEFORE the barrel and slide start to rise. At that point, the barrel and slide have moved to the rear only about a tenth of an inch, and while a little force has been pushed into the recoil spring, the base of that spring is resting against the frame and there will be some push BACK against the frame.
https://youtu.be/ySO0EWIlOKc
It's only later as the momentum (of the slide continues to move back and changes the balance of the gun, and the barrel separates and is moving down at the breech end and up at the crown) that you start to see much vertical movement. But the bullet left the barrel earlier. Judicious use of the stop/start button will show you a lot. Lots of clicks very quickly!! Bore axis seems to be a bigger player than anything.
The next video is very good -- but they also experiment with a lot of different video capture speeds. This video is more of a demonstration of some awesome videographic gear and technique than a study in handgun ballistics -- you can watch it all if you like, or you can just go to the two points mentioned below.
If you jump ahead to about 7:40 in the video you'll see the semi-auto fired while being videoed at a very high frame rate. Look closely and you'll that the barrel hasn't risen but the barrel and slide have moved back just a bit. At about 8:04 you'll see it all repeated, with the videographer telling you where to look to see the bullet. The bullet is gone but the barrel/slide are still perfectly horizontal.
https://vimeo.com/48571597
A heavier bullet moves down the barrel more slowly, to be sure, but that it's moving more slowly doesn't really change how the gun functions. A semi-auto's action is a MECHANICAL process, based on equal and opposite reactions.
It's all mechanical at that point: dependent on how far things have moved, not how FAST they're moving. It would seem that velocity, which can be indirectly affected by bullet weight, is a far more important factor in point of impact position than weight. Maybe folks focus on weight and ignore velocity in these discussions. As noted above, gravity is a constant and it doesn't care how heavy the bullet is.
After the bullet is gone the forces at play continue to move the barrel and slide to the rear. The barrel is forced away from the slide (with the rear of the barrel dropping down and the other end rising. The weight of the slide pushing back on top of along the top of the gun (bore axis) and the force of the recoil starts to raise the entire gun a bit.
While its going up, it doesn't have any effect on point of impact -- the bullet is long gone. Proper technique can also keep barrel/gun rise to a minimum. Jerry Miculek's videos address this topic.
The Mythbusters TV Show has a video on YouTube; they pay more attention to the gases coming out of the barrel than recoil. They cut the video off before the bullet has moved very far, but their video clearly shows the bullet several inches in front of the muzzle, with no visible rise/vertical movement of the barrel or slide. If nothing moves vertically before the bullet exists, bullet weight is clearly not a factor in recoil and barrel rise.
What I'd like to see is whether, in a semi-auto, two bullets of different weights have the same point of impact if fired at the same velocity. In theory, they should. Recoil will be felt differently by the shooter.
https://youtu.be/7y9apnbI6GA?t=2
-----------------
I'd also like to understand whether a revolver is really all that different than a semi-auto BEFORE the bullet leaves the barrel...
Most folks seem to feel there is a big difference. Others also feel that heavier bullets make a difference, too -- as does the lack of a moving slide and barrel. They may be right, bu ]t the evidence supporting that position isn't clear to me, yet. (As is probably obvious to some of you, I can be "slow" to understand some of this stuff...)
Super Slow Motion videos of revolvers being fired are much harder to find than similar videos of semi-autos. Many of the videos show the amount of recoil with different calibers and different loads, but nobody pays much attention to points of impact.
Revolvers typically recoil more than semi-autos firing similar loads -- but that seems to because most revolvers have a very high bore axis. In watching videos of revolvers, most of that higher-bore-axis induced recoil seems to occur AFTER the bullet is gone! Super slow motion videos might resolve that issue, too, but I can't find any that are helpful (or slow enough.)
The only video that sort of addressed the issue was the following, which shows both a semi-auto and revolver being fired underwater. Shooting a gun underwater is NOT the same as shooting a gun above water, but much of the recoil-related "physics" could be similar. ( I don't know whether the heavier density of water affects recoil differently, or whether it affects a semi-auto differently than it affects a revolver.)
Look at 3:00 to see a semi-auto being fired, and then at 6:00 to see a revolver being fired. There isn't a noticeable difference -- but because it's water, not air they're both being fired in, the heavier density of water may play into to this differently...
Warning you must watch a brief ad -- but you can skip it after 3 seconds:
https://youtu.be/OubvTOHWTms
I have seen photos of someone firing a .357 Magnum offhand, and then with the barrel/frame wired down to a heavy rest so that there is no recoil. They don't show whether the points of impact are different. I wasn't able to find that video, today.
Here's a video of a revolver being fired (.357 Magnum), and if you press the start/stop button carefully you can catch the barrel AFTER the bullet has exited, and it doesn't seem to rise much more than a semi-auto. Perhaps a hair more, and given the effect of a fraction of a minute of angle, that COULD affect the point of impact.
(You also see what happens when they fire a dud round, and push the gun down! Bad technique!!)
https://youtu.be/c_AmpNimp-Q
My claim was that because the heavier bullet was moving slower, the barrel rose a bit before the bullet was fully out of the barrel, and that raised the point of impact. That seemed intuitively obvious to me and to others, here.
JohnKSa and other said, "no, that isn't so". It appears I was wrong and he/they were right.
Well, I'm here with some convincing evidence supporting their position. I've found a number of super-slow motion videos of semi-autos in action, and it seems to confirm their point. If you think I'm waffling when I say "seem" or "seems" rather than saying "it proves they're right," my choice of words is based on observations that could be in error, but I don't think that's the case. The following videos seem pretty convincing to me.
As I was looking at the following videos I also looked at revolvers -- and the claim that recoil tended to be a bit different there, too. I have found nothing to suggest that revolvers are really all that different. I can understand why they MIGHT be different, but it seems that MOST of the difference may come into play AFTER the bullet has left the barrel. That's a different topic, and we can ignore it for the moment -- and I'll address it again, at the end, below the "-----------------".
When looking at Semi-Autos, here's what I found:
In semi-autos the slide and barrel move together to the rear as the bullet goes down the barrel. That was the earlier claim.
The only motion visible in the ultra high-speed videos is of the slide and barrel slightly moving to the rear until AFTER the bullet has exited the barrel. The slide and barrel don't start to rise UP gas is coming out of the barrel, and the barrel and slide has gone more to the rear, and started to separate. At THAT POINT the bullet is already gone.
Before the bullet exits the barrel, some of the rearward movement of the slide is likely transferred to the recoil spring and to the frame - but even that small amount of energy is a transfer of force that is primarily to the rear, and it has no up or down effect.
If the barrel doesn't rise until AFTER the bullet leaves the barrel, bullet weight or bullet speed down the barrel isn't affecting the barrel or slide's vertical position. That kills my earlier claim.
Bullet weight does affects bullet performance after it leaves the gun. But, a light bullet fired from a gun and a heavy bullet fired from a similar gun will both hit the ground at the same time if they're both fired from the same height and level, and exactly at the same time.
But if the light bullet is moving faster, it will hit a closer target more quickly than a heavier bullet (because gravity hasn't been working on it as long), and that lighter bullet should hit higher than a heavier bullet because it hits the target more quickly and has less time to be affected by gravity.
The point overlooked in this comparison, however, is whether the two rounds are loaded to be delivered at the same velocity. If the velocity is the same, they'll both get there at the same time. Felt recoil might not be the same, but felt recoil won't have any real effect until the bullet is out of the barrel...
Gravity is a constant, and it doesn't care how heavy the bullet is. The only difference between the hot or heavy round and a light or slower round is how far the bullet travels before it hits the ground. When shooting at targets, the round's elapsed time to target affects where the point of impact will be, all other things being equal. A faster round will get there more quickly and be less affected by time/gravity.
Here are several videos that seem to offer proof:
The first one is of a 1911, and if you click the stop/go button on the bottom left of the video, you can stop the motion. If you do it just right, you'll see that the bullet leaves the barrel BEFORE the barrel and slide start to rise. At that point, the barrel and slide have moved to the rear only about a tenth of an inch, and while a little force has been pushed into the recoil spring, the base of that spring is resting against the frame and there will be some push BACK against the frame.
https://youtu.be/ySO0EWIlOKc
It's only later as the momentum (of the slide continues to move back and changes the balance of the gun, and the barrel separates and is moving down at the breech end and up at the crown) that you start to see much vertical movement. But the bullet left the barrel earlier. Judicious use of the stop/start button will show you a lot. Lots of clicks very quickly!! Bore axis seems to be a bigger player than anything.
The next video is very good -- but they also experiment with a lot of different video capture speeds. This video is more of a demonstration of some awesome videographic gear and technique than a study in handgun ballistics -- you can watch it all if you like, or you can just go to the two points mentioned below.
If you jump ahead to about 7:40 in the video you'll see the semi-auto fired while being videoed at a very high frame rate. Look closely and you'll that the barrel hasn't risen but the barrel and slide have moved back just a bit. At about 8:04 you'll see it all repeated, with the videographer telling you where to look to see the bullet. The bullet is gone but the barrel/slide are still perfectly horizontal.
https://vimeo.com/48571597
A heavier bullet moves down the barrel more slowly, to be sure, but that it's moving more slowly doesn't really change how the gun functions. A semi-auto's action is a MECHANICAL process, based on equal and opposite reactions.
It's all mechanical at that point: dependent on how far things have moved, not how FAST they're moving. It would seem that velocity, which can be indirectly affected by bullet weight, is a far more important factor in point of impact position than weight. Maybe folks focus on weight and ignore velocity in these discussions. As noted above, gravity is a constant and it doesn't care how heavy the bullet is.
After the bullet is gone the forces at play continue to move the barrel and slide to the rear. The barrel is forced away from the slide (with the rear of the barrel dropping down and the other end rising. The weight of the slide pushing back on top of along the top of the gun (bore axis) and the force of the recoil starts to raise the entire gun a bit.
While its going up, it doesn't have any effect on point of impact -- the bullet is long gone. Proper technique can also keep barrel/gun rise to a minimum. Jerry Miculek's videos address this topic.
The Mythbusters TV Show has a video on YouTube; they pay more attention to the gases coming out of the barrel than recoil. They cut the video off before the bullet has moved very far, but their video clearly shows the bullet several inches in front of the muzzle, with no visible rise/vertical movement of the barrel or slide. If nothing moves vertically before the bullet exists, bullet weight is clearly not a factor in recoil and barrel rise.
What I'd like to see is whether, in a semi-auto, two bullets of different weights have the same point of impact if fired at the same velocity. In theory, they should. Recoil will be felt differently by the shooter.
https://youtu.be/7y9apnbI6GA?t=2
-----------------
I'd also like to understand whether a revolver is really all that different than a semi-auto BEFORE the bullet leaves the barrel...
Most folks seem to feel there is a big difference. Others also feel that heavier bullets make a difference, too -- as does the lack of a moving slide and barrel. They may be right, bu ]t the evidence supporting that position isn't clear to me, yet. (As is probably obvious to some of you, I can be "slow" to understand some of this stuff...)
Super Slow Motion videos of revolvers being fired are much harder to find than similar videos of semi-autos. Many of the videos show the amount of recoil with different calibers and different loads, but nobody pays much attention to points of impact.
Revolvers typically recoil more than semi-autos firing similar loads -- but that seems to because most revolvers have a very high bore axis. In watching videos of revolvers, most of that higher-bore-axis induced recoil seems to occur AFTER the bullet is gone! Super slow motion videos might resolve that issue, too, but I can't find any that are helpful (or slow enough.)
Note: if you look at videos of the Chiappa or Matebba revolvers, which have the barrel aligned with the bottom of the cylinder, their recoil seems to be similar or even less than! most semi-autos shooting similar loads!! These guns have VERY LOW BORE AXES!
The only video that sort of addressed the issue was the following, which shows both a semi-auto and revolver being fired underwater. Shooting a gun underwater is NOT the same as shooting a gun above water, but much of the recoil-related "physics" could be similar. ( I don't know whether the heavier density of water affects recoil differently, or whether it affects a semi-auto differently than it affects a revolver.)
Look at 3:00 to see a semi-auto being fired, and then at 6:00 to see a revolver being fired. There isn't a noticeable difference -- but because it's water, not air they're both being fired in, the heavier density of water may play into to this differently...
Warning you must watch a brief ad -- but you can skip it after 3 seconds:
https://youtu.be/OubvTOHWTms
I have seen photos of someone firing a .357 Magnum offhand, and then with the barrel/frame wired down to a heavy rest so that there is no recoil. They don't show whether the points of impact are different. I wasn't able to find that video, today.
Here's a video of a revolver being fired (.357 Magnum), and if you press the start/stop button carefully you can catch the barrel AFTER the bullet has exited, and it doesn't seem to rise much more than a semi-auto. Perhaps a hair more, and given the effect of a fraction of a minute of angle, that COULD affect the point of impact.
(You also see what happens when they fire a dud round, and push the gun down! Bad technique!!)
https://youtu.be/c_AmpNimp-Q
Last edited:
(And single shots.)
