special and magnum loads, same point of aim

[buck460XVR]

If the gun recoiled while the bullet was still in the barrel, any heavy recoiling gun would shoot high. I sometimes shoot a 480 Ruger with full house 355 gr. bullet loads at 50Yds. If the gun recoiled while the bullet was in the barrel, how can I even hit the black much less the center of the target, airplanes would be in danger. Think about it. All those big bore handgun hunters would go hungry. But they don't . I stand by my opinion , bullet is out of the barrel before recoil starts.

Me thinks you need to shoot that .480 more often and with a larger variety of bullet weights. Barrel dwell is measured in nano-seconds. If you fired your .480 horizontal to the ground at shoulder height by the time it recoils to the point there is enough muzzle lift for you to even perceive, the bullet has already hit the ground a little over 200 yards away, long before the time the muzzle reaches it's peak during recoil and is aimed at the sky. Big bore hunters don't go hungry because they understand barrel dwell, not because it doesn't exist. They know they need to re-sight the handgun when changing bullet weight or powder charge enough to significantly impact amount of recoil. The reason you can hit the black at 50 yards even with barrel dwell is that you've adjusted your sights to accommodate the change in POI caused by it. The amount of difference caused by barrel dwell can range from hardly noticeable to readily apparent and is influenced by barrel length, difference in bullet weight and difference in powder charge. I shoot my .460 generally at 70 yards. At 70 yards the difference in POI from a 200 gr bullet going 2200FPS and a 300 gr bullet going 1500 is over 12 inches.....with the 300 grainers shooting higher than the 200s. The 200s are going faster and drop less, but still the 300s shoot a foot higher. It ain't flinching, it's barrel dwell and increased recoil.

Correct. It'd defy the rules of physics otherwise.

Also, the ever popular "dwell time" is a red herring. It's true the lower-velocity bullet stays in the barrel for a longer period of time, but it's also true that the muzzle rises with a correspondingly lower velocity; the result is that muzzle rise between a fast and slow bullet of the same mass is the same. In other words, when considering normal handgun distances, neither velocity nor dwell time affect POI - mass of the bullet (as well as gun mass and barrel length) does, with the heaver bullet hitting higher.

If the bullet weights are the same and there is lower velocity, there is less recoil. So even if the amount of barrel dwell is increased, the amount of recoil and muzzle lift is deceased. This is why at shorter ranges, lower velocity ammo of the same bullet weight impacts lower. Less muzzle rise. Now take a much heavier bullet and shoot it at the same velocity and while you haven't changed dwell time, you have increased muzzle rise because of increased recoil. Heavy bullets take more powder, recoil more, and generally less velocity, thus have more muzzle rise and dwell time. It's not the mass of the bullet that influences POI, but the amount of recoil/muzzle lift and velocity.

Here's a better explanation than I can give.....

It goes like this. When you fire any weapon, the laws of physics come into action full force. Ever heard the one that says "For every action, there is an equal but opposite reaction?"

Upon firing, the powder begins burning and builds pressure which forces the boolit out of the case and down the bore, eventually to leave the muzzle and fly toward it's target. At the same time, the pressure that forces the boolit forward, forces the receiver backwards. Here comes the equal but opposite part.

Since most firearms will move in the shooter's grip under this opposite reaction, the muzzle lifts, which affects point of impact. When you "sight in" a particular load, your sight adjustments will generally compensate for this movement. It's just a part of shooting. As you shoot heavier boolits, there is more movement produced since it takes more energy to force the heavier boolit down the bore, and therefore the resulting equal but opposite reaction causes more muzzle lift, and the sights must be re-adjusted to compensate for the additional movement in order to strike the target at the intended point of impact.

For a revolver, especially a single action revolver with fixed sights where there is no adjustment, choosing a powder/boolit combination that will "shoot to the sights" is critical. Too fast or too light a boolit will leave the muzzle before the recoil lifts it far enough to strike point of aim on the target because it has less dwell time (time in the barrel from the moment of ignition to exiting the muzzle) and will "shoot low." A heavier boolit takes longer to speed up because it requires more energy to break the force of intertia and start the boolit moving in the bore, so it has more dwell time, and the muzzle rise in the shooter's hands is greater, causing the heavier boolit to "shoot high."

Here's a relevant vid on the subject:

It's a video on the subject, but not relevant at all. The dude actually contradicts himself by displaying that lower recoil ammo impacts lower. While velocity has an affect on dwell time, amount of recoil/muzzle lift has more. He didn't get it at all and his demonstration does nuttin' but confuse. When one decreases velocity and decreases recoil/muzzle rise, POI may remain similar because those changes cancel each other out. We don't see this as much in rifles because rifles don't pivot on our shoulder like a handgun pivots in our hand.

 

[Jack B.]

You should give Ruger engineers a bit more credit: "Intrinsic Recoil" has been factored into the design. If you look at a revolver from the side, draw a horizontal line between the top of the front and rear sights, you'll see that the barrel is actually pointed down. Think about it.

This gun recoils more than that. Sorry I don't buy it. I've watched and seen and done so much shooting that I'll stick with my opinion. I'm convinced the bullet is out of the barrel before recoil starts.

 

[someguy2800]

If you look at this video you can see the gun is moving up and back while the bullet is still in the barrel.



I did the math in a previous post and if the front of a 4 inch barrel rises by .010" it will change point of impact at 25 yards by 2.25" so a very small amount of movement is all that's needed

 

[someguy2800]

This video you can see it really clearly if you pause it frame by frame that the front sight come up like an 1/8" before the bullet leaves the muzzle.

 

[MrBorland]

If the bullet weights are the same and there is lower velocity, there is less recoil. So even if the amount of barrel dwell is increased, the amount of recoil and muzzle lift is deceased.

The velocity of the muzzle lift is decreased by a corresponding amount - multiply the lower recoil velocity by the longer dwell time, and you get the same net recoil distance during that dwell.

Here's some real data from a recoil calculator, using some reasonable input:

.38 special:
Bullet weight in grams: 158 grains
powder charge in grains: 4.0
Velocity in fps: 800
weight of firearm in pounds: 2.5

velocity of recoiling firearm 8.14 fps
dwell time: 0.42 milliseconds (= 4 inches / 12 inches per foot / 800 fps)
distance muzzle traveled during dwell = 0.04" (= 0.00042 seconds * 8.14 fps * 12 inches per foot)

.357 mag:
Bullet weight in grams: 158 grains
powder charge in grains: 14.0
Velocity in fps: 1200
weight of firearm in pounds: 2.5

velocity of recoiling firearm 14.0 fps
dwell time: 0.27 milliseconds (= 4 inches / 12 inches per foot / 1200 fps)
distance muzzle traveled during dwell = 0.04" (= 0.00027 seconds * 14.0 fps * 12 inches per foot)


ergo - the distances the muzzle traveled during the dwell are essentially the same, despite the difference in velocity and recoil. Again, it's because the longer dwell is balanced against a slower recoil velocity.

Now do the above analysis while altering bullet mass (125 and 158 grains) and leaving MV the same (1200 fps). Dwell time is the same, but since the gun shooting the lighter bullet recoils with less velocity (10.9 vs 14 fps, respectively), it moves correspondingly less during dwell time. IOW, mass, not velocity affects POI.

 

[macgrumpy]

I watched those videos and I have to say that your perception isn't the same as mine, I don't see any muzzle movement before the bullet leaves the bore.

I did a frame by frame analysis as you recommended and you are flat out wrong.

FRAME 0 This is just before ignition


FRAME 40 The bullet has left the bore and the both the bore and the bullet are the same centerline which proves that there is no muzzle rise at this point


MUZZLE RISE OCCURRED AFTER THE SLIDE REACHED IT'S REAR MOST TRAVEL


Additionally, you guys keep reciting Newton's Laws but you take them out of context. When the bullet is still in the bore the combination of gun and bullet is called a closed system, meaning that there are no outside forces on the system, only the forces inside the gun. The force that creates the movement is the expanding gases within the closed system. That force is applied equally in all directions. That means that while the bullet is pushed forward the gun is pushed backward with equal and opposite force (Newton's Third Law) which causes there to be no resulting force on the center of mass - the gun doesn't move. As long as all of the forces are internal of this closed system, the gun wont move but if you add force externally (the shooter moves or gasses escape between the cylinder and forcing cone of a revolver or gasses are pushed out ahead of the bullet) then the gun will move.

 

[macgrumpy]

The velocity of the muzzle lift is decreased by a corresponding amount - multiply the lower recoil velocity by the longer dwell time, and you get the same net recoil distance during that dwell.

Here's some real data from a recoil calculator, using some reasonable input:

.38 special:
Bullet weight in grams: 158 grains
powder charge in grains: 4.0
Velocity in fps: 800
weight of firearm in pounds: 2.5

velocity of recoiling firearm 8.14 fps
dwell time: 0.42 milliseconds (= 4 inches / 12 inches per foot / 800 fps)
distance muzzle traveled during dwell = 0.04" (= 0.00042 seconds * 8.14 fps * 12 inches per foot)

.357 mag:
Bullet weight in grams: 158 grains
powder charge in grains: 14.0
Velocity in fps: 1200
weight of firearm in pounds: 2.5

velocity of recoiling firearm 14.0 fps
dwell time: 0.27 milliseconds (= 4 inches / 12 inches per foot / 1200 fps)
distance muzzle traveled during dwell = 0.04" (= 0.00027 seconds * 14.0 fps * 12 inches per foot)


ergo - the distances the muzzle traveled during the dwell are essentially the same, despite the difference in velocity and recoil. Again, it's because the longer dwell is balanced against a slower recoil velocity.

Now do the above analysis while altering bullet mass (125 and 158 grains) and leaving MV the same (1200 fps). Dwell time is the same, but since the gun shooting the lighter bullet recoils with less velocity (10.9 vs 14 fps, respectively), it moves correspondingly less during dwell time. IOW, mass, not velocity affects POI.

Please explain where you came up with your calculations for muzzle travel during dwell.

 

[Jack B.]

If you look at this video you can see the gun is moving up and back while the bullet is still in the barrel.



I did the math in a previous post and if the front of a 4 inch barrel rises by .010" it will change point of impact at 25 yards by 2.25" so a very small amount of movement is all that's needed

flinch , trigger jerk ,shooter mistake, bullet long gone before recoil. Obvious. Made my point. Thanks.

 

[someguy2800]

Here is the revolver video I posted at 20% speed with a line drawn just above the front sight.



In the semi auto video I can't see that the gun makes any upward travel but I noticed the slide does move a small amount.



Can we talk about making 357's and 38 specials shoot to the same spot now?

 

[Jim K]

Above (#4), I wrote "In fact the change was due to less barrel time for the faster bullet, allowing the gun to recoil more and the bullet to strike higher.
The first part of the statement is correct, but the underlined part is wrong, and I apologize. It is the slower bullet that will take more time to get out of the barrel, so the slower (not necessarily heavier) bullet will strike to point of aim in a fixed sight revolver, where the faster bullet will shoot lower, hence the police found that the new +P+ loads shot lower, with the result I described.

Jim

 

[CraigC]

The rule of thumb is that for a given velocity, heavier bullets impact higher (due to greater recoil). For a given bullet weight, lower velocities impact higher (due to longer dwell time).

Now you can argue the physics behind it until the cows come home but most folks will find the rule of thumb to bring true. I certainly do. I have had guns that were dead zero at 25yds with full pressure 240gr .44Mag loads that would sling the same bullet right over the target when the velocity was reduced to 800fps with .44Spl's. Same if we go the other way, increasing velocity ALWAYS lowers point of impact. Increasing bullet weight ALWAYS raises point of impact, sometimes to the point that we need taller front sights to shoot with heavy bullets.

Any slow motion video depicting a semi-auto is irrelevant. In a revolver, recoil forces are acting directly against the shooter. In a semi-auto, they are working against the slide, which must at least begin moving backwards before any recoil forces are transmitted to the shooter. This, coupled with a typically lower bore centerline, are why semi-autos tend to have MUCH shorter front sights than revolvers.

 

[buck460XVR]

Please explain where you came up with your calculations for muzzle travel during dwell.

Same here.....and what direction was the travel? Back/up/combination? Was there any human attempt to control recoil and muzzle lift? Sorry but claiming that a 158 bullet will impact the same spot regardless of muzzle velocity at reasonable target ranges(15-40 yards) just does not hold true from my experience. Why with some of my fixed sighted handguns I've had to adjust powder charge to shoot to POA. Why I've had to change height of adjustable sights when changing power level of ammo with the same projectiles. I've found that sometime changing my grip on the revolver will impact where it hits on the target as far as vertically. I always assumed it was because I was changing the fulcrum point of it's recoil.

The rule of thumb is that for a given velocity, heavier bullets impact higher (due to greater recoil). For a given bullet weight, lower velocities impact higher (due to longer dwell time).

Now you can argue the physics behind it until the cows come home but most folks will find the rule of thumb to bring true. I certainly do. I have had guns that were dead zero at 25yds with full pressure 240gr .44Mag loads that would sling the same bullet right over the target when the velocity was reduced to 800fps with .44Spl's. Same if we go the other way, increasing velocity ALWAYS lowers point of impact. Increasing bullet weight ALWAYS raises point of impact, sometimes to the point that we need taller front sights to shoot with heavy bullets.

^^^This reflects my experiences also.

I shoot a lot of different loads in my revolvers/handgun caliber carbines. Many times I will shoot 38s in the .357s using the exact same bullet. Never do they impact the same. Sometimes they are close, with the upper level .38s generally being the closest to lower level .357s, but they do vary. Sometimes for just shooting balloons/bowling pins or other reactive targets it is not enough of a difference to bother changing the sights. But because of the accuracy needed for the distances I intend to shoot, I sight in my revolvers used for deer hunting with ammo from the same batch I will be hunting with.

 

[MrBorland]

a 158 bullet will impact the same spot regardless of muzzle velocity at reasonable target ranges(15-40 yards) just does not hold true from my experience.

And this is all the OP was really asking. I chimed in with my experience (that I see a different effect), and that it was consistent with what I was expecting. Beyond what I've already offered, I'm not going to help derail the thread by persuading anybody anything. If POI is different between different ammo, fine with me, and I don't doubt anyone. It's a deceptively complicated subject. At any rate, it's good those who's experience differs from mine have taken steps to insure they know how their POI changes with differing ammo.

 

[BobWright]

From my experience: I have a Ruger Super Blackhawk .44 Magnum. I sighted it in with a 240 gr. JHP @ 1400 f.p.s., using a 6" dia. bullseye and a 6 o'clock hold at 25 yards, shots hitting dead center. This put me on target using an 8" dia. (estimated diameter) bull at 100 yards. This was a B-8 target, I think, on a wooden frame made of 2 x 2 wood, with the crossmember of the frame bordering the target paper.

Switching to a 180 gr. JHP @ 1700 f.p.s. my bullets went between the legs of the target frame, some 12" ~ 14" low.

Draw your own conclusions.

Bob Wright

P.S. What are y'all calling "dwell time?" My bullets seem to get going as soon as I bust a cap.

 

[CraigC]

P.S. What are y'all calling "dwell time?" My bullets seem to get going as soon as I bust a cap.

How long the bullet takes to get down the bore.

 

[BobWright]

How long the bullet takes to get down the bore.

Thank you, Sir. Never heard that term used before. Always heard the term "barrel time."

Thanks for elucidating.

Bob Wright

 

[BobWright]

For whatever its worth, I've held my gun with the sights at the 9 o'clock position and using a 3 o'clock hold, also held the gun upside down and used a 12 o'clock hold. When I did my part, the bullet hit the center of the bullseye.

This during my "exhibition shooting" phase.

Bob Wright

P.S. Should you wish to try this, I'd suggest using a milder recoiling gun until you get the hang of it.

 

[GooseGestapo]

Revolvers and semi-autos are very different animals.
With the revolvers, the breach is fixed, and recoil is instantaneous with cartridge ignition.

With a recoil operated (including blow-back) semi-auto, you first have the slide moving rearward and recoil sensation and effect doesn't occur till the slide reaches its full rearward travel contacting the frame, and transferring the momentum to the frame, effecting recoil. Hence, most semi autos have fixed sights. A M1911 .45 will typically shoot most bullet weights to same poi, however, a heavier bullet will induce torsional twist greater than a lighter bullet, causing a change in lateral impact.
For instance, I had to drift the rear sight of my .40 Shield to the right, as the mid-range 155gr and 135gr I shoot bullets cause less "twist" than a full velocity 180gr bullet, it came from factory sighted for...

Yep, physics at work. Newtons laws!

 

[someguy2800]

The torsional twist is something I never thought of with a revolver. You can really feel it shooting a contender.