ShotMarker caliber not precise?

[davidjoe]

Yes, it is. Great weekend of shooting. A .22 benchrest Saturday and a 600 Fclass Sunday, both went well. Both got me thinking about something they have in common.

Score ring shooting has a quirk. The center of our shot can clearly miss the ring, but we get credit if the edge of our bullet touches the ring. I call it a quirk because a bullet that only tangentially touches a target doesn’t really do anything, but anyway. Years ago we had gauges made up for ranges in every conceivable caliber to help iron out tricks played on the eyes.

Yesterday, I shot a .284. The system was open to caliber changes, which I requested shooters make after saving, before we started. On my last match, I was shown a 150-8X. But, the default was .308. Although no one would have said anything, I re-ran it suspecting a 149-8, and indeed that’s what it was.

But here’s what’s new, that I have not seen analyzed, before.

Just how precise is the ShotMarker’s center to edge placement? Extremely, relative to our caliber increments, it turns out.

So by the eye on a phone screen I surmised that I’d lose on the difference between a 7mm and a 7.62 mm bullet. Remember, it’s actually half the difference because there is as much bullet on the irrelevant side of the center.

It turns out that if I shot a .292 caliber on up, it’s a 150.



If I shoot a 291 caliber, on down, it’s a 149.




Walking that in showed a ShotMarker is capable of seeing a gulf of difference between a 30 cal and 7mm. We are talking on the order of magnitude of 24 one thou gradations between the two, (half of that which impacts score) and then drawing a circle that is capable of splitting those gradations in half. A 7mm only “reaches” out from its center 92.2% as far as a .30 does, and a 6, only 78.9%.

.22 BR at 50 yards fits in oddly to the discussion. We want this, but it doesn’t always happen.



On a “P” for .22 pinned and magnified target, we get just as much credit for this, which clearly is not “as good” a shot.




This shot below is almost identical to the pinned shot. The pinned shot and it both come much closer to each other than they do to the first picture. It however is properly a -1.





It’s tempting to round to 30 for all assuming it can’t tell a difference but, looks like it can, many times over. Preserving these small differences does make .22 BR a blast to shoot. If a guy used a 30 cal, the difference in score would be tremendous.

An open mic ShotMarker might indeed not put the center exactly where the paper hole would say it is, relative to other shots and the target center, but it’s thought to put the center of each shape, speed and size bullet in the same starting place as each other, our part being the manual caliber selection, and it sure can draw an amazingly precise circle that is no doubt finer than the pixels on any screen.

 

[kzin]

I lost a point changing from 243 to 224

 

[Bottom Fodder]

Does that not somewhat level the playing field? If all were set at say 308.
I don‘t have a dog in this hunt

 

[davidjoe]

Does that not somewhat level the playing field? If all were set at say 308.
I don‘t have a dog in this hunt

It does have that effect, but it ought to be neutral instead, because pulled targets that are manually marked are all scored by whether the higher value ring is touched by the shot or not; and when switching to etargets, using the single caliber choice for all rifles “enlarges” the ShotMarker’s representation of the bullet hole of all the calibers used that are smaller than the one selected, which deviates from passively recording edge distance to the scoring ring. On a pulled and scored target holes would be physically gauged by a plug of their actual caliber, when too close to call, so a divergence is occurring.

The ShotMarker cannot discern the actual diameter of the bullet and relies on the caliber information inputted. We see in videos of big matches, and in accounts of club matches conducted in many places, that the “administration features” are typically locked, making for a more smooth and efficient progression, but when so, this means that all targets are preset to a single caliber.

There’s an inherent accuracy benefit to the smaller calibers that always interplays with what they give back to the “environment” when scored at great distance. The thought would be that the interplay is physically a real one, involving strategy and choices, that the scoring system would be impartial to.

 

[Bottom Fodder]

thanks, so if a lower score ring is touched do you get the lower score?

 

[Ned Ludd]

Does that not somewhat level the playing field? If all were set at say 308.
I don‘t have a dog in this hunt

IMO - it does not "level" the playing field. One cost-benefit to using a larger diameter bullet is heavier weight versus the larger hole; i.e. having to deal with greater recoil versus a potential positive effect on scoring. Assigning a .30 cal hole to individuals using a much lighter bullet provides them with a benefit that comes at no cost in terms of recoil management. Of course, lighter and smaller diameter bullets often have lower BCs, but that's an additional difference above and beyond the weight versus caliber issue I'm describing. If someone wants the benfit of the larger .30 cal hole in their target, then they should actually be using a .30 cal bullet and experiencing both the potential benefits and negatives associated with its use.

A perfect example of this scenario would be the two calibers used in F-TR; namely, .223 Rem and .308 Win. I shoot both and I can tell you that the difference in recoil between typical F-TR loads using these two caliber is substantial. In fact, the relative lack of recoil shooting 90+ gr bullets in the .223 Rem can allow for noticeably enhanced precision over a much heavier recoiling .308 Win with 200+ gr bullets. It's enough to make a difference, especially at distances of 600 yd or less where the benefit of the increased BC of the 200+ gr .30 cal bullets is much less significant.

Even as a regular .223 Rem shooter in F-TR matches, I believe allowing someone using a smaller diameter bullet to use the .30 cal bullet setting of an e-target provides an unfair advantage. The trade-off is that many match directors do not want the added hassle of setting the system for the bullet diameter used by each individual shooter, or they may not want to unlock the software so each shooter can input their bullet diameter individually because of the potential for bad things to happen with the system when a bunch of different people have access to all the internal software controls. Thus, it's not uncommon to find the systems set for .30 cal holes across the board at F-Class matches.

I suspect the more common issue some people have with the ShotMarker is not the diameter of the bullet hole, but the actual placement of the center of the bullet hole. Even if the diameter of the hole is spot on according to the unit, points may be dropped if the shot placement isn't accurate, meaning the center of the hole.

 

[Bottom Fodder]

So if I shot say a 6 Dasher I would get the benefit of less recoil but not the benefit of a larger hole that I would get from say a 308

 

[davidjoe]

thanks, so if a lower score ring is touched do you get the lower score?

No in Fclass, it’s only a question of whether the higher value ring has been touched, or not. The bullet hole can sit 100% beside the next higher ring, and touch it at exactly one “tiny” spot, - a single tree cell worth of paper, and that counts for the higher score.

Since I opened the door on the .22’s, I should say that there is in fact a variation of .22 scoring ring matches shot at 50 yards, where touching the inside of the lower value ring does give you exactly that score. But that’s not scored by a ShotMarker.

 

[Gater]

back in the day when I first started shooting service rifle I was shooting an AR while most where using the M-1A. According to NRA rules .223 holes where to be plugged with a .30 cal plug that has since been changed

 

[ChrisNZ]

.. a variation of .22 scoring ring matches shot at 50 yards, where touching the inside of the lower value ring does give you exactly that score. ..

It's called "outward gauging" in these parts. In the distant past in smallbore (rimfire) shooting, I think they used to do inward gauging but changed to outward when scores were maxing out too often.

 

[kzin]

With modern digital technology we often get falsely high precision.

The shot may be recorded to 16 digits but that's kind of silly when the accuracy is only 2 or 3 digits.

 

[Spoonbill]

Kick ass targets

 

[Rick Ratzlaff]

Interesting conversation. There is one significant issue that nobody here has understandably brought up. The hidden physics is the precision of the E-target. The factor between the reported X&Y and the actual can be very different depending on environmental conditions which can change moment by moment.

 

[davidjoe]

…. It seems that we all have an equal chance of a random environmental deviation occurring in the plotted shot placement, and that it’s really only going to matter if we are somewhat close to a line. X’s are the hope of course, and we are plenty safe in that 5 inch disk at a thousand, but horse races usually get decided by a nose at the line.

It’s tempting to say that since the shot could be or is misplotted by more, there’s no harm, but that error will actually go both ways and even out to a net zero, averaged over thousands of shots and hundreds of matches for each of us, while the caliber bump on the other hand, will remain, is cumulative, and is a one-way edging toward the center, only capable of improving scores; if it were “group size” caliber choice wouldn’t matter, but it’s an inside edge game.

To my thinking if it’s the liners, and really only them, that make or break us, then the plus 8% for a 7mm hole ranging to a plus 21% for a 6mm added to the actual hole size, is really quite a bit to look past. Keeping it exactly straight is definitely the function of the ShotMarker that is the most precise, as shown above, if we choose to use it.

Kind of ironic to think about, but if the the ShotMarker couldn’t account for caliber differences, we’d probably all be complaining how roughshod it operates in that regard and blurs outcomes at the lines, but when it can differentiate, and to its credit exceedingly well, we are tempted to disable it.

 

[Bottom Fodder]

Are “E targets” use in major National matches

 

[davidjoe]

Are “E targets” use in major National matches

When at Lodi, yes, but otherwise no, not at Raton, Avery, or Camp Atterbury. Lodi is likely a bit small in number of target frames to host nationals, but a neat range that actually extends behind 1k to allow 1,200 yard shooting.

 

[morpheus]

NRA Long Range Nationals for Conventional Prone will be fired on e-targets at Atterbury this year. I think this is year 2 or 3 for this scenario, and I believe Mid-Range is also fired on e-targets. Not sure about Across the Course.

 

[kzin]

CMP National Prone Smallbore was held on e-targets this year.

Kongsberg(?sp)

Camp Perry does some events with the etargets but more still with pits.