Eagle Eye vs Gehmann Scoring Gauge

Eagle Eye vs Gehmann Scoring Gauge:


Hello everybody:

I recently purchased a Gehman Scoring Gauge pictured here to assist in scoring targets:

Gehmann Illuminated Scoring Gauge – 141 – Intershoot


A couple of people have told me that it is inaccurate, that it has too large a scoring ring on the glass and the good old Eagle Eye is the way to go.  

Well, I would like to verify that myself before I take it on their word.  

 I got my trusty Eagle Eye out and examined them with the etched surface on the etched surface of each gauge and examined them. 

Sure enough, the Gehmann 22 gauge is slightly larger then the Eagle Eye.  

Scoring targets, I compared multiple bullet holes using each and there was a good number of bullet holes that scored a "10" with the Gehmann that only scored a "9" on the Eagle Eye.  

Ok, then I got a scoring plug with magnifying lens and upon using the three gauges on the same targets, there were a higher number of "10's with the Gehman then with the plug.  But, there were more 10's with the plug then with the Eagle Eye.  

Then I considered the temperature and what effect the ambient temperature would have on the accuracy of each gauge, the stainless steel plug would probably have the higher coefficient of thermal expansion then either the Gehmann or the Eagle Eye.

Time to take a breather, Cranky!

Basically, I know that each scoring gauge will not score the same target the same.  

Now I am questioning how I verify the accuracy of each of the three gauges.  

Micrometer?
Steel Gauge?
Lead Bullet?
Calipers?

Back story:

One of the leagues that I shoot in is very competitive.  The score of the top four shooters are totaled for the team score and in the 20 years I have been shooting the league, there have been quite a number of combined scores within 10 points of each other, and there have been a handful of matches that used the X count to determine the winner.  In close matches, each target is examined carefully by the captains of the team and an associate.  Every team has a handful of Eagle Eyes and nobody has ever questioned the accuracy of the Eagle Eye until a couple of us purchased the Gehmann Illuminated Scoring Gauge.  Up until now, everybody has assumed that the Eagle Eye is correct but now we have another scoring gauge that does not jive with the Eagle Eye.  Which one is correct?

My gut feeling is the plug is the most accurate but the plug is not allowed as a primary scoring tool for our league, only after a question is raised and the captains are informed is a plug used.  

Realistically it is a very friendly and fun league but we are sticklers to details.  

Regards, 
Crankster

I don't think you will find accurate "mathematical" answer to your question.  IMHO, proper answer would be in line with very same as one behind the reason your league doesn't allow plugs - it is matter of policy that your league instilled.  Hence I would choose one, and stick with it, mandating all teams within league use the same scoring tool.  If shooters within league are interested to have more 10s / Xs, maybe using Gehmann would please everyone. 

Now, another approach might be asking the governing body of your league (presumably CMP or NRA) what is their acceptable standard.  After all, I presume, your league submits results and shooters get qualified based on it.

My 2c.

AP

We've noticed the same thing in our club - the Gehmann is ever so slightly larger and calls "in". The current theory is that it does not press down on the paper quite as tightly, and the magnifier alters the visible diameter of the hole.

The Eagle Eye has a different issue - it has two unmarked circles, for .22 and .177, and many shooters inadvertently use the wrong one. And because it presses down firmly, some feel it damages the hole.

The NRA rules explicitly say "plug", and that it can only be used by an official, inserted once, and the decision is final. That doesn't fly well either. But plugs definitely alter the hole and make challenges, well, a challenge.

Bottom line, agreed with AP - make a rule and do that, every time.

[edit] BTW Champion's Choice also sells the Gehmann (and all the other) gauges: https://www.champchoice.com/mc-range-equip/scoring-gauges/gehmann-scoring-gauge-with-illuminated-reticle-g141

In benchrest we used scoring plugs.  Targets were placed on a light box and any questionables were plugged and inspected with a magnifier.  If the plug (0.224") touches the ink it gets the ring.

Similar to this:  https://www.champchoice.com/mc-range-equip/scoring-gauges/22cal-scoring-gauge-with-magnifier-13322m-133

Well Hell, let’s just throw in the electronic (optical) devices also for comparison.

Plug, Eagle Eye, or German Gizmo, it’s always subject to some issue, the Eagle eye is placed by trying to center the hole in a smaller circle in the gauge.  This is a matter of subjective idea of centering.  A plug is placed into the smaller hole, but it doesn’t necessarily follow the actual axis the bullet transversed through the target.  The Eagle Eye being seemingly smaller, to my mind it makes some sense that a false ‘ten” is less probable.  

In spite of all of this, if the shot is questionable, my gut tells me to call it out unless it can be proven otherwise.  Especially in relatively lower importance events like indoor leagues.  Otherwise we just become arguing about nothing important.

I know people want targets scored correctly but when you get to the point of needing an Eagle Eye or some other high dollar fancy dancy looking device that is not what "Bullseye" is about. I have always scored by the rule if it is close enough for one of the fancy gizmo's I give it to the shooter EVERY time!!!!!! And with that said you wonder why some people never come back to Bullseye.  We sometimes are our own worst enemy!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

NRA overlays are pretty accurate and you can use 2 overlays to find those hard to determine doubles if needed. 
Stan

NRA Rule 14.3 calls for the scoring gauge to be .2225" - .2240".  The Eagle Eye guaranteed size is .221" which makes is too small to officially score the target.

I recall a post years ago from a HM saying if it takes more than 5 seconds looking at a shot, it is in.

Jack H wrote:I recall a post years ago from a HM saying if it takes more than 5 seconds looking at a shot, it is in.

Yes, this. The same as the HM that mentored me when I started told me.
If I have to think about it for more than two or three seconds the shooter gets the benefit of the doubt and it's in. Use overlays to see shot up scoring rings and doubles.

If league is that fussy about points, it may be time for the members to pony up for an acoustic scoring system.

Jees:

So much anger and criticism directed towards the original poster (me).  Had to check and make sure I was not on Sniper's Hide.


With one of my leagues a postal league, we send our scores in via email and I want to make sure that the scores we are reporting are accurate and verifiable.  It comes down to the principals of honesty and integrity, which are basic cornerstones of our sport.  

Do not know if any of you guys have ever been involved in a league where there were a couple of dishonest competitors, but it is not pretty. Completely destroyed the league although a couple of teams survived and formed a much smaller league.  

When I am scoring a target, I do not care if it is a 94 or a 96, I want to make sure that if somebody sees me scoring their target, they will have no question that the score recorded is accurate.  This is especially important for a new shooter who is tracking their progress every match.  Last thing we need is a discouraged shooter who got a score that does not represent what they shot.   

You guys have a great day. 

Geo

That’s what the challenge system is for.

And yes, any scoring aid that doesn’t alter the target( penetrates) is legal to assist the scorer.
I won’t quibble about the .0005 out of tolerance of the eagle eye, nor the wide line/narrow line targets.

I think the rule books have dimensions of what a scoring plug should measure. I suggest to validate relative sizes of the optical gages with a couple of gage pins, laying the gage on the end and comparing. For the plug, measuring with a micrometer. I think that you will determine what is what.

John, pass the popcorn, please...