TargetTalk

I had been using 25 yd T&R centers on our local indoor range until I found out it is only 20 yards. I ordered some 20 yard targets. While 20 yards is 80% of 25 yards the target black X-10-9 rings on the 20 yard targets are only 68% of the size of the 25 yard targets. A 25 yard T&R black is 5.5". 80% of that would be 4.4". But the 20 yard T&R black is only 3.75". These are official NRA targets.
I am sure there is some mathematical reason for this but I can't figure it out. Does anyone know why the 20 yard scoring rings are so much smaller?

Well, that shows the differences but it still does not explain why there are differences.

MajD;

I may be totally wrong but will take a shot at answering your question.
Never really thought about it until now.

I believe it has to do with having the same sight picture.

If a target is a certain size at said distance then if you bring it closer the target black and scoring rings become smaller to get the same visual effect.

Using math and percentages is not the same as vision interpretation.

Hope this makes sense, maybe not, I am still thinking about it, damn it...

Clarence

The simple reason is the the bullet diameter does not change size with distance. Therefore, to get the same scoring potential as you move from 25 yards to closer to the shooter, the rings have to get decreased for the distance and the bullet diameter since the bullet just has to "touch" the scoring rings to get that score.

The size of the black is visual only, not for scoring and therefore the diameter of the black will vary for distance only, and to the closet scoring ring for that size.

Opinion part, since I have not done the match, but I think I remember they used the .38 caliber as the average to do the additional reduction. At least I think so and that's why that B-16 is so much harder with a .22 than it is with a .45, at least for me.

Cecil R.

OK, I will explain.
If you look at the link above, the guy did take into account the bullet diameter (though I have not verified if he did it correctly).

In short, it is not the diameter of a scoring ring that scales, but rather the sum of the diameter of the scoring ring (D) plus the diameter of the bullet (d). Say, the size of the black is D1 at distance L1, then for the value of the same shot to remain the same at distance L2 there must be a relation satisfied

(D1+d)/L1=(D2+d)/L2,

from which a simple conversion formula follows

D2=D1*(L2/L1)-d*(L1-L2)/L1.

For L1=25yds and D1=5.32" (slow fire black) you get
D2=4.21" at L2=20yds in case of a .22 bullet and
D2=4.17" in case of a .45 bullet
The actual diameter of NRA is 3.73", which is smaller than both.

When you scale down from 25yds to 50ft the same thing is seen.
Slow fire: 3.47" for .22 and 3.40" for .45 instead of the official 3.07".
Sustained fire: 3.62" for .22 and 3.54" for .45 instead of the official 3.06".
Another obvious discrepancy is the fact that the black on 25yds slow fire is smaller than on T/R, while it is reverse (slow fire's is bigger) for 50ft. That obviously cannot be explained by any scaling and indicates that it was NRA's intention to make shooting at shorter distances harder.

Note that the USA Shooting does not have this and all the rings on International targets simply scale by the above formula. I hope this clarifies it better than the link I posted initially.

Yes, I saw that and it needs a correction for 2 items, I think. Again, I never took the time to do anything but what follows, but please see if this addresses the issues. I doubt the NRA would have done anything as simple as just the math, they would also have to have included the "scoring potential" of a shot where the projectile size does not change with the distance.

Therefor I think the math is correct except for the real application of a bullet hole in the target. Again, this is for scoring rings, not the black. The black just seems to be the closest rings that get a similar size black, and for some reason, it is not very good at that.

To correct the application of the formula for actual shooting requires application of the bullet hole after the initial distance potential scoring ring is determined.

Yes, the diameter of ring + the bullet diameter is used to get the "potential" ring size at the yardage, say 3.36 10 ring at 50, which is 3.36 +.357 (actually .357/2 on either side representing the center of the bullet to visualize this properly) = ring to be reduced. That is the standard distance for slow fire.

Take to 25 yards for B-16, you get about 1.858, then subtract .357 (actually .357/2 on either side to visualize properly) to move that potential size down until a .38 bullet will just touch to get that score. You get about 1.50 (I think since I'm doing this from memory). I guess the tolerance stacking gets it to 1.51 for a B-16 10 ring, but I never took the time to check.

I never checked further than this.

Cecil

Cecil,

The formula D2=D1*(L2/L1)-d*(L1-L2)/L1 takes care of everything. The second term (the one proportional to the bullet diameter 'd') corrects for the fact that the bullet diameter stays the same no matter how far the target is.

The International reduced distance targets
http://www.usashooting.org/library/Rule ... N_TECH.pdf
could all be checked to obey by that formula. NRA's conventional targets, on the other hand, do not. Since, as you correctly pointed out NRA staff were unlikely to make simple math errors, it was clearly done on purpose.

My guess is that it was done to make classifying for a higher rank more difficult at tournaments shot at non-standard (20 yd, 50 ft) distances. To the contrary, USA Shooting does not award classifications, and only really care about a handful of National level matches shot at proper distances anyway.

Shaky, my post was not in response to yours, but the general comments above.

The formula you have and my description are the same. I just hate the "student can easily see this reduces to process", reminds me of calculus where it was a simply way of saying I was going to be spending the next hour trying to figure it out.

Anyway,

The formula works with a .357 bullet and the the slow fire target rings given by the NRA for 25 yds, 20 yds and 50 ft. based on a 3.63 inch 50 yard 10 ring starting point for reduction (well, within a few .01's) Well, at least it did for the 10 ring and I quit looking after that. I'm not worried about the other rings too much.

The formula does not work for the scoring rings for the Timed and Rapid fire targets, they are approximately +0.3 inch smaller (based on calculations for the 10 ring). Therefore the T/R could be considered harder, although I never found it so. I'd like to know the reasoning for the reduction or calculation.

The size of the black for the NRA appears to follow the closest approximation of the nearest ring sized based on starting from 50 or 25 yards for slow or T/R as near as I can see.

There, I think I'm done thinking about this for now. I will be asking Dennis the next time I see him about the T/R process. It may just be because.....

Cecil

Hmm? I'm not all that hot at math any more. Have any of y'all checked the TQ6 and TQ7 targets we shoot at 25 FEET at our local range for our monthly bullseye league? They seem so tiny and so close. I wonder if they scale down also?

Cecil,

You are right in that the 10-ring scales correctly for the .357 bullet diameter, for slow fire from 50 yd to 50 ft. 7-ring definitely not (see above), and I have not checked all others. Pretty funny. It would be interesting to find out from NRA how 50 ft targets were established historically. If they still remember, of course.