Theoretical Groups at Distance

[JW.]

I have a indoor range that is limited to 40 yards (48 if I diagonal), I use it to test regulator settings and for verifying tins of pellets prior to the more relevant outdoor testing.

If I shoot a ten shot group of 1/2" (outside to outside) at 40 yards (a 0.323" group ctc), how close would the theoretical ctc group of 0.444" be at 55 yards (indoors)?

Can I expect some additional expansion of the group?

Back calculating to 10 yards I get a 0.081" ctc group (half a pellet), which seems close to actual if not slightly larger than... That is what got me thinking about the additional expansion, it is expanding more further away from the muzzle.

Has anyone calculated tested groups at 40 yards and then confirmed the theoretical size at 55 yards?

 

[beerthief]

Personally i just go shoot @ required distance , lot easier on the brain and just way more fun too .
Theory is just that , no extenuating circumstances just perfection IN THEORY .

 

[JW.]

Yeah, cute (and worthless) comment, see it's not that 'easy', i'm not doing several hours in the car just to get that extra 15 yards.

I've won a couple Grand Prix Championships and a National Championship (plus countless State Championships) using this limited indoors distance as my ground zero for testing...

 

[JEFFPPC]

It's not linear and yes it will be bigger. Random thoughts and theorys don't win. Testing and practice wins.

 

[Racer88]

You can't extrapolate theoretical groups at a longer distance based on performance at a shorter distance.

I can shoot sub-1/2-MOA at 100, 200, and even 300 yards with one of my "powder burner" rifles. But, it's a whole other "ball-o'-wax" at 600 or 1000 yards. I won't be shooting 1/2-MOA or even 1-MOA groups or even 2-MOA at 600 or 1000 yards.

There is no linear correlation or extrapolation possible in practical / real world experience. I would expect the same to be true for air rifles at air-rifle-distances.

You've won national championships.... This question doesn't "jive" with that kind of experience / background. Puzzling.

PS.... Another "cute and worthless" comment, I'm sure!

 

[thomasair]

You can extrapolate 40 to 55 just fine.

I've done it at 25 then checked at 50 and it was very very close.

Mike

 

[6gun]

I have a indoor range that is limited to 40 yards (48 if I diagonal), I use it to test regulator settings and for verifying tins of pellets prior to the more relevant outdoor testing.

If I shoot a ten shot group of 1/2" (outside to outside) at 40 yards (a 0.323" group ctc), how close would the theoretical ctc group of 0.444" be at 55 yards (indoors)?

Can I expect some additional expansion of the group?

Back calculating to 10 yards I get a 0.081" ctc group (half a pellet), which seems close to actual if not slightly larger than... That is what got me thinking about the additional expansion, it is expanding more further away from the muzzle.

Has anyone calculated tested groups at 40 yards and then confirmed the theoretical size at 55 yards?

I would say theoretically yes the groups would increase in size as range increases, if there are no other variables. I think of my groups as the base of a cone. If the group is 1/2 inch at 15y I would expect it to be around 3 1/2 inches at 100y or worse.

This is why when setting guns up with my 15 yard indoor range I don't explore setups that won't shoot 1 hole or 1 ragged hole depending on what the gun shows me for it's personality(or how expensive it was).

 

[rdtricks]

Just for giggles, you could shoot several groups at 20 yards, then an equal number of groups at 30 yards, and finally groups shot at 40 yards. Take the measurements of each group, at distance, and average the group sizes. Then compare the average group sizes looking at the percentage of change. This should allow you a rough extrapolation on how your groups grow over distance. With the average percent of growth it may also allow you to predict grouping growth at given distances - within reason.

 

[Struckat]

Most of my shooting is in the basement at 10 meters.

At that distance I can tell if a barrel hates a pellet. No point in trying farther if it won’t shoot @10m.

This does not mean that one that does well @10 will do any good @50

 

[JW.]

You can't extrapolate theoretical groups at a longer distance based on performance at a shorter distance.

I can shoot sub-1/2-MOA at 100, 200, and even 300 yards with one of my "powder burner" rifles. But, it's a whole other "ball-o'-wax" at 600 or 1000 yards. I won't be shooting 1/2-MOA or even 1-MOA groups or even 2-MOA at 600 or 1000 yards.

There is no linear correlation or extrapolation possible in practical / real world experience. I would expect the same to be true for air rifles at air-rifle-distances.

You've won national championships.... This question doesn't "jive" with that kind of experience / background. Puzzling.

PS.... Another "cute and worthless" comment, I'm sure!

So then sub MOA doesn't really mean anything apart from the distance you shot it at?

To say you have a "sub MOA" gun is a LINEAR correlation. A very common expression would you say?

Yes, i've won and this question and discussion is common among experienced competitive shooters.

So then if you are not having these conversations since you believe they have no basis, are you then winning AAFTA GP Championships and National Championships? You must be right?

 

[JW.]

I would say theoretically yes the groups would increase in size as range increases, if there are no other variables. I think of my groups as the base of a cone. If the group is 1/2 inch at 15y I would expect it to be around 3 1/2 inches at 100y or worse.

This is why when setting guns up with my 15 yard indoor range I don't explore setups that won't shoot 1 hole or 1 ragged hole depending on what the gun shows me for it's personality(or how expensive it was).

Same here with the cone. I think i'm seeing some additional expansion as I get further away, this is why I referenced the sides of the cone as curves instead of straight lines (yes, an odd way to explain it). We know for sure the groups won't get smaller... lol

 

[JW.]

Just for giggles, you could shoot several groups at 20 yards, then an equal number of groups at 30 yards, and finally groups shot at 40 yards. Take the measurements of each group, at distance, and average the group sizes. Then compare the average group sizes looking at the percentage of change. This should allow you a rough extrapolation on how your groups grow over distance. With the average percent of growth it may also allow you to predict grouping growth at given distances - within reason.

That was part of the data collection process. 10, 26 and 40 simply because they are the distances I needed to verify (well 10 and 26). It was the 10 yard group that was the odd one, difficult to know if its a half a pellet or not but it seems right.

 

[JW.]

You can extrapolate 40 to 55 just fine.

I've done it at 25 then checked at 50 and it was very very close.

Mike

Thanks Mike, proof will be in the pudding when I get out to distance tomorrow.

How have your experiences been lately with LW's slow twist poly stainless steel 177 barrels?

 

[Racer88]

So then sub MOA doesn't really mean anything apart from the distance you shot it at?

To say you have a "sub MOA" gun is a LINEAR correlation. A very common expression would you say?

Honestly, I don't understand your question.

A "sub-MOA" gun relates to the gun's mechanical potential. But it means nothing if it's in the hands of Mr. Shakey McFlincher.

As distance increases, so do the effects of shooter error, ammunition load inconsistencies, and other factors such as wind. So, naturally it's easier for a shooter to achieve a sub-MOA group at 100 yards than it is at 300 yards, and even harder at 500 yards, etc. So, a shooter that can shoot <1-MOA at 100 yards may not be able to achieve it at 300, 500, 800 yards. So, that's why I submit extrapolation or assumptions based on shorter distance results are not valid.

In my short time / limited experience with air rifles, the most obvious difference I noticed is that pellets are MUCH more susceptible to wind, even at relatively short distances. I suspect there's some variability in the air pressure behind the pellet, depending on the rifle quality. The difference in my precision from 25 to 50 yards is noticeable. 100 yards? VERY noticeable.

So then if you are not having these conversations since you believe they have no basis, are you then winning AAFTA GP Championships and National Championships? You must be right?

Again, I'm not sure what you're asking here. But I would expect someone who wins rifle championships to be knowledgeable and not ask questions about the basics of marksmanship, nor would I expect such a champion to suggest that if a shooter can achieve a certain measure of precision at a short distance then we can assume the same level of precision at longer distances. I definitely disagree with that, for the reasons previously mentioned.

It is entirely possible that I have misunderstood your questions and comments.

I've had many many many conversations related to long-range precision rifle shooting. While I have a fair bit of experience in precision shooting (from 100 - 1000 yards), I was very turned off by my experiences with organized competition (the people / culture), so I terminated that pursuit. They were not nice to me or my daughter. At all. It was clear they were not interested in welcoming newcomers to their competition. That's a whole other conversation.

 

[thomasair]

He's asking about 40y to 55y.....Not 100y to 1000y.

In terms of moa...shooter error won't magnify at longer distances. If you have a 1 moa wobble....it's 1 moa at any distance.

Since he's talking about indoors....surely wind isn't a factor.

Mike

 

[Racer88]

In terms of moa...shooter error won't magnify at longer distances. If you have a 1 moa wobble....it's 1 moa at any distance.

True... 1 MOA is 1 MOA at any distance. I'm not suggesting otherwise. What I AM suggesting is that errors introduced by the shooter (among other factors) increase over distance. Shooter wobble isn't the only factor affecting precision.

In any case, I'm out. Good luck to the OP!

 

[JW.]

True... 1 MOA is 1 MOA at any distance. I'm not suggesting otherwise. What I AM suggesting is that errors introduced by the shooter (among other factors) increase over distance. Shooter wobble isn't the only factor affecting precision.

In any case, I'm out. Good luck to the OP!

The idea of doing this preliminary testing indoors is to remove all the factors that would typically add imprecision into the mix. Super solid bench, rest, bag, etc. good light, no wind, no parallax errors, as pure groups as possible to vet a new barrel (I didn't sort, weigh, clean or lube pellets). As others here have mentioned they have indoor areas they use to do the same type of testing, I guess i'm pretty luck to get to 40 indoors.

But, how to you get a sense of what those groups would be at 55 yards if all I have is 40?

It is very common to discuss the extrapolated group size that you would see at 1000 yards from a group shot at 500 yards (I can pull up countless references to this) or from 100 to 200 for powder burners. What is not discussed is just how different those extrapolated groups are compared to the actual shot group at 1000 yards (crickets in terms of online references).

This is why I made the post.

Nothing uncommon is being asked or represented, its not under my experience or competitive level to make such a post (and even if it was it still does not take away from my competitive record). I only mentioned my competition experience because someone flippantly responded unaware of the validity or point of the post and having no idea who's posting or what experience they have (this is pretty common on this forum). If they were smart they'd start paying attention, it's what I do.

The ironic part is you had a chance to possibly learn something but you're leaving the discussion without understanding the discussion... That's a bummer honestly and you'll notice I didn't call your post cute or worthless, I addressed it with serious answers and some questions as examples to help you think it through because that is what happens in field target.

I'm hoping to take as much luck out of the equation as possible, however a little luck is always part of doing well on the course.

 

[JW.]

Since he's talking about indoors....surely wind isn't a factor.

Not yet...

I do have at least a half dozen box fans.

 

[d3vnull]

My simple mind says that:

1. You can prove it mathematically with pythagorean theorem and similar triangles

2. Or swag it. If 40' is a 1" group then divide by 8 to get 5 yard change.

35' is 7/8"
45' is 1 1/8"

That is my 15 minute thought pattern.

 

[Motorhead]

IMO using a slow twist .177 poly with 10.3 to 13.4 weight pellets at the speeds we shoot to stay sub 20 fpe, high pellet rpm is not an issue and gyroscopic stability degradation we see with some faster twist combinations IS NOT an issue here.
As such the questioned last 15 yards ( 40 to 55 ) should see a very similar accuracy trend with all the shots taken in a similar fashion and conditions.

As another with accolades in winning matches and one who preps guns and barrels for other competitive shooters .. I'll stand by my opinion & continue to do .. what I do