Ballistics Mystery

[Twystd1]

Marmaduke?

[LynnJr]

In Frank Leonard and Marmaduke mode.
Bullets hit higher on the target as the velocity increases not lower. Barrel harmonics make the groups grow and shrink but the higher velocity rounds still hit higher.
A tuner or Muzzle Weight will dampen and broaden the barrels harmonics shrinking the groups but the higher velocity rounds will still hit higher if the Shooter is holding the gun correctly.
The late Jerry Tierney who was an engineer and tested bullets for Sierra and Berger told me in a lightgun that faster shots would hit lower from time to time. At the 2010 1000 yard Nationals we set up his Oehler chronograph and had Wally Larsen and Dangerous Bob Dorton Gary Child's and several others mark four targets.
I shot two 6 Dashers a 300 WSM and a 300 Ackley at 1000 yards.
Each shot was numbered and matched up to the chronograph reading.
The extreme spreads were all less than 10 fps and all the shots hit lowest to highest on the target and followed the velocity readings exactly as expected.
The test results were posted on the F-Class forum visited by that gang of shooters.

[AFTII]

Bullet behaviour doesn't change in small yardage changes like 50 yards.
Convergence takes place around a node due to very small muzzle angle change and a very small velocity variation. The slower shots are in the barrel longer so they leave the muzzle at a steeper angle and converge with the faster rounds.
Barrel harmonics affects the vertical spread of your group.
The bullet is still hitting higher on the target but only groups well near a node.
If the barrels muzzle is moving downward the slower rounds that are in the barrel longer will not converge with the faster rounds and that is why you get big groups.
If you map it out from your lowest velocity to your highest velocity as the velocity increases the rounds will print higher but will only group well near a node.
When you add a tuner to a barrel it will compensate for a larger velocity variation because the mass added to the end of the barrel dampens the harmonics and flattens and widens the node.

Technically its the anti-node and not the node. The node is the area of highest angular velocity. Hence the more likelihood of dispersion if the rounds do not leave the barrel at the exact same time.

The anti-node is the area of lowest angular velocity, i.e., the top and bottom of the curve where angular velocity hits 0 just before reversing direction. It's the anti-node that gives the least dispersion. Carry on.

[AFTII]

Jack, I just don't think we have enough data to explain what you are seeing. I'll throw this out there because I've seen it happen on more than one occasion.

Optics. Optics are prone to fail at the least opportune time. Optics can cause a 8 min dispersion. They can cause scenarios where two shots are touching and one is off in the stratosphere.

I've had all manner of scope failures ranging from having the cross hairs fall completely out of the focal plane to having the gun suddenly throw unexpected fliers. Nothing sucks more than to drive 1500 miles to a benchrest match only to discover that the cross-hairs fell out. (My dad had similar issues with a scope on his elk rifle from flying.)

In my opinion the biggest cause of optics failure is high frequency vibrations, like the vibrations you experience when driving or flying. I drove from CA to TX in a motorhome to shoot a BR match only to get there to find that my scope took a complete **** on me from the drive.

If I were you, I'd definitely explore that possibility.

P.S. All scopes fail, even the $3K ones. Although I have seen cheap scopes fail from recoil alone, it's usually not recoil that kills them. Its vibration that kills them.

[Ishooter]

I'm with the others that say you'd need a chronograph if you're a serious reloader. It's cheap for about $100. Easy to set up & use. It helps you to know what your loads are. If you're looking to duplicate factory loads or even better than factory loads, or want to know why your loads are different from factory loads, then get a chronograph. Many factory velocities posted won't show that with your gun. Also, if you reload for accuracy, then you'll need a chronograph. It helps you to see how consistency your loads are.

Once you have a chronograph, it'll open up a lot interesting things about shooting and reloading.

[bsumoba]

I don't know if anyone mentioned this, but could it just be that the gun does not shoot small groups? I would like to also point out that you did not shoot a whole lot of shots. It could be that your gun is a 1-2 minute shooting gun, at which point both loads are shooting near the same point of aim. Could it be that your rifle is just not accurate enough. My friend has a R700 that will not shoot less than a minute no matter what he tries.

We all think that our guns shoot like lasers and that where we aim is where the bullet will go. Wrong...

You have to remember that we are still shooting a group and the better guns will shoot 1/4 minute (with tuned loads), most custom guns will shoot 3/8-1/2 minute with a decent load and factory rifles could be just plain ugly no matter what you put down the barrel.

As you go farther out, many other things come into play like mirage, wind conditions, etc and at that point, the shooter is mainly to blame if the gun is shooting horribly (bad shooting position, bad wind reading, pad point of aim, etc).

Technically its the anti-node and not the node.

That is why I usually say "accuracy" node

[LynnJr]

Technically its the anti-node and not the node. The node is the area of highest angular velocity. Hence the more likelihood of dispersion if the rounds do not leave the barrel at the exact same time.

The anti-node is the area of lowest angular velocity, i.e., the top and bottom of the curve where angular velocity hits 0 just before reversing direction. It's the anti-node that gives the least dispersion. Carry on.

I worked RF Microwave for 22 years so I do know the difference.
If you follow Dr Geofrey Kolbe on his Compensation Theory it is the anti-node.
If you follow the world's best Rimfire Gunsmith Bill Calfee you want the NODE and not the anti-node at the crown of the barrel and not the typical 2.5-2.75 inches back it is routinely at.
I follow Bill Calfee because his guns win more big matches than all the other Gunsmiths combined and following his instructions I won a big match in 2010.

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm

Here is a combined article that explains what Al Harral and Dr Kolbe have to say but not what Bill Calfee has to say. Bill doesn't use the correct terminology so the engineers turn there noses up but none of them can tune a rifle like he does. When he says stopped muzzle he wants the node which looks stopped in a standing wave at the crown nothing more nothing less. If you follow his writings I am that Lynn or WaterBoy for the last 25 years.

[JustEd]

Great point, entirely posssible. Also I would expect that given the same bullet weight the slower load would print higher, not lower. More dwell time in the barrel.

Thanks for getting it right!

[LynnJr]

Thanks for getting it right!

Wow just Wow!!!
Slower rounds hit higher? So my 308 subsonic loads will hit higher than my max loads as long as I use the same weight bullet?

[bsumoba]

Wow just Wow!!!
Slower rounds hit higher? So my 308 subsonic loads will hit higher than my max loads as long as I use the same weight bullet?

I think they are talking about a specific situation, which is shooting at 50 yards, with a 100 yard zero...or at least I hope that is what they are saying. Otherwise, it does not make sense.

If you have a 100 yard zero AND you shoot at 50 yards, then yes, the slower bullet might hit a little higher; and that is only because of how the scope is zero'd and the trajectory of a bullet relative to the yardage you are shooting at.

If you hypothetically had a zero 1 yard away from your muzzle, then at 50 yards, the higher velocity round will hit higher.

If you have a 50 yard zero, then 100 yards out, the faster bullet will hit higher.

Whoever thinks that a slower bullet will hit higher needs to share what they are having because in most cases, that would defy physics.

[JackEllis]

I was going to go out this morning to shoot 4 groups of 3 rounds each, one with Remington Core Lockts, one with Wolf FMJs, one with the original hand load (longer OAL0, one with a slightly shortened hand load (.055). Objective number 1 was to see how each load grouped. Objective number 2 was to see where they grouped. The wind came up early so I switched to prepping the deck for it's annual coat of stain.

I appreciate all your suggestions, advice and patience. Hopefully I'll have some more information in a few days once the weather calms down. It's supposed to snow overnight with more possible snow next weekend. What happened to spring?

[diver160651]

I think they are talking about a specific situation, which is shooting at 50 yards, with a 100 yard zero...or at least I hope that is what they are saying. Otherwise, it does not make sense.

If you have a 100 yard zero AND you shoot at 50 yards, then yes, the slower bullet might hit a little higher; and that is only because of how the scope is zero'd and the trajectory of a bullet relative to the yardage you are shooting at.

If you hypothetically had a zero 1 yard away from your muzzle, then at 50 yards, the higher velocity round will hit higher.

If you have a 50 yard zero, then 100 yards out, the faster bullet will hit higher.

Whoever thinks that a slower bullet will hit higher needs to share what they are having because in most cases, that would defy physics.

[Flouncer]

Thanks Lynn, now I need some aspirin. Kidding !!!

[LynnJr]

What everyone is missing is the OP is shooting solids. I have never seen solids hit where lead core bullets hit. I have never seen them change 3 inches but 1.5 is quite common.

Flouncer
If you where to use a machine rest and go from book minimum to book maximum at 100 yards most chamberings would have a vertical spread under 3.5 inches.
I think BSumoba is on the right track with his rifle capability theory. Solids can be finicky and if they are out of tune the groups can be large.
When Warren Jensen first came out with his balanced flight J40 bullets I bought $2000 worth and the smallest 100 yard group I shot was 9 inches. I had to trim the meplats back to 0.055 inches before they would group which defeats there use.

[TMB 1]

Great point, entirely posssible. Also I would expect that given the same bullet weight the slower load would print higher, not lower. More dwell time in the barrel.

Really noticeable in pistols at short range with cartridges like the 44mag. The faster flatter load hits lower at close range and hits higher at long range. The slower load hits higher close range and lower long range.