Scatt problems

[Guest]

I've been trying to use a scatt system usb pro, and keep having the same problem. I'll be shooting say prone and have a steady hold dead center going 1/2 way out to the 9 ring and when I shoot the lines will stay in the same hold but it'll show the shot as many a 5 rings away with no lines leading to or from it. Is there something I'm doing wrong or what? Thanks

[David Levene]

What have you got the f-coefficient set at. Sounds like it might be too high.

70-80 seems to be a reasonable starting point if you are using Scatt to simulate a match.

If however you are using Scatt to check and improve your technique I am still of the opinion that the f-coefficient is better set at zero.

The f-coefficient introduces a variation based on such things as gravity, atmospheric conditions, projectile efficiency etc. In other words the things that come into effect after the shot has left the barrel. I do not consider them to play any significant part in checking or correcting your technique.

[PaulT]

David, I have never understood the actual merit of setting the f-coefficient to anything but zero as it is an electronic training for developing technique.

I don't know if this coefficient includes barrel acceleration at time of the shot being fired, is it this coefficient that factors and predicts the likely shot impact resulting from such movement?

Has a consensus been reached on what f-coefficient should be used for 10m air pistol and for shorter distance training [with the known parallel –v- angular error] of 25m pistol and 50m pistol shot with sensor at 10m.

[David Levene]

I don't know if this coefficient includes barrel acceleration at time of the shot being fired, is it this coefficient that factors and predicts the likely shot impact resulting from such movement?

I never really managed to get a straight answer out of them on this. If it is included then I don't think it should be. Why group something that can be calculated in with other things that can't.

[Fabio]

You should think the f-coefficient as a "quality" of your "ammo" who can show some unpredictable groups.

Even the better ammo suited for the better barrel and shooting indoors can land on the target forming a not so perfect group.

Try differents f-coefficient searching for groups you see on testing ammo, for more "real" felling or just forget the "shot-hole" and analyse the very end of the trace.

[David Levene]

...... or just forget the "shot-hole" and analyse the very end of the trace.

You beat me to it Fabio, I had just realised that I did not mention this in my response to PaulT and came back to make that very point.

[Guest]

F coefficient accounts for the projectile deviation from the theoretical hold due to lateral velocity vector at the time of the shot. It has nothing to do with adding random noise due to ammo variation.

If the barrel moves during the shot, by the time the projectile hits the target, it will not be where the barrel was pointed (hence away from the trace). An infinitesimal but fast jerk will send the shot into 8 even though the sights would look like they've been inside 10.5 all that time.

Such deviation is actually a function of lock+barrel time and projectile velocity, but instead they chose to use only one variable, so everyone now has to mess with it manually until it approximates their gun.

Setting it to zero does nothing except masks the triggering errors.

[dflast]

F coefficient accounts for the projectile deviation from the theoretical hold due to lateral velocity vector at the time of the shot. It has nothing to do with adding random noise due to ammo variation.

If the barrel moves during the shot, by the time the projectile hits the target, it will not be where the barrel was pointed (hence away from the trace). An infinitesimal but fast jerk will send the shot into 8 even though the sights would look like they've been inside 10.5 all that time.

Such deviation is actually a function of lock+barrel time and projectile velocity, but instead they chose to use only one variable, so everyone now has to mess with it manually until it approximates their gun.

I came to the same understanding checking out my own Scatt. If you look at the locations of the virtual shot hole and of the aiming trace at the instant of trigger release you'll see this in action: when F = 0 the shot falls right at the end of the trace, and as you increase F, the "hole" is displaced in the direction the trace was moving, the more F (and the faster the trace was moving) the further the displacement.

I tuned Scatt to my AP by live firing at the full 10m, and then fiddling with shot parameters until the virtual targets most closely resembled the paper ones. In my case F = 8. Note "most closely resembled." Scatt is not an electronic match target and you'll drive yourself to distraction trying to make it one.

David

[David Levene]

It's a shame that Scatt seem to have removed the definitionof the f-coefficient, what it is actually designed to do, from their web site.

I have emailed them for a copy and will post it here if/when I get an answer.

In the meantime I seem to remember that Scott Shaffer's definition in his manual for Scatt was pretty much a word-for-word copy from the Scatt site.

[Guest]

F coefficient accounts for the projectile deviation from the theoretical hold due to lateral velocity vector at the time of the shot. It has nothing to do with adding random noise due to ammo variation.

If the barrel moves during the shot, by the time the projectile hits the target, it will not be where the barrel was pointed (hence away from the trace). An infinitesimal but fast jerk will send the shot into 8 even though the sights would look like they've been inside 10.5 all that time.

Such deviation is actually a function of lock+barrel time and projectile velocity, but instead they chose to use only one variable, so everyone now has to mess with it manually until it approximates their gun.

Setting it to zero does nothing except masks the triggering errors.

This is how I understood the F coefficient to work too - but the definition in the Scott Shaffer manual disagrees.........

[Guest]

Sorry, I missed this bit in the Scott Schaffer manual referring to F coefficient:

"this is affected by a number of factors that include things such as........... ........the speed and direction of the movements of the firearm caused by pulse and nerve related movements"

So mixed in with all the random stuff is this VERY important variable.

To simulate bullet dispersion you could use the "Bullet SCATT" variable which seems to add some adjustable randomness to the fall of the shot.

[David Levene]

So mixed in with all the random stuff is this VERY important variable.

That's exactly my point and is why I suggest setting the f-coefficient to zero, ignoring the shot hole and then analyzing the data. Scatt gives you the speed of movement so it is easy to see which are the good shots in this respect and which are bad. It also gives you solid data to work with, rather than just looking at a hole positioned away from the trace. If the speed is 120mm/s at shot release it is obvious that the shot hole is going to be further away from the trace than one with 80mm/s.

To simulate bullet dispersion you could use the "Bullet SCATT" variable which seems to add some adjustable randomness to the fall of the shot.

If you are looking at bullet dispersion then yes, Scatt does have a dedicated function for ammunition variations. The f-coefficient includes for other items which, although they affect the shot placement, are not necessarily related to ammunition variation.

As I previously said, if you just want to simulate a match then the f-coefficient is a useful tool. If however you are using it purely as a training tool then I consider it much more beneficial to set the f-coefficient to zero, ignore the shot hole and just use the data supplied.

[KennyB]

Hi Dave,
all I will add is that, for me, using SCATT and seeing the shot fall outside the hold pattern, due to being released while the barrel was in motion, was one of the things that transformed my shooting. A real revelation. I still use the mantra "wait for the still moment". It works for me anyway.

This effect explains a lot of unexplained flyers that less experienced shooters produce. Training to release the shot when there is minimum lateral velocity is one of my top tips.
Yes, I'm in favour of the F coefficient.

(The other revelation was how staring at the sight picture for too long can create a false image - also gleaned from SCATT. But that's another story.)