about accuracy

A place for general potato gun questions and discussions.
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bravootome
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Wed Dec 30, 2020 2:11 pm

i opened this topic looking for some answers about what to do ( that i have not done ) for accuracy....
specs : 6.01 500 mm barrel ( 450mm, 550,mm, 600 mm.........)
0.5 g quality bbs
optisan scope( 2 tasco, 1 buschnell (?), 1 no name,1 old russian made ww2 one)
stainless steel very well put together construction
70- 100 bar used pressure
diferent hammer springs for diffrent fps
and no hop-up system
+ i eliminated dust from inside .

what i tried so far : 4 6.01 barrels
5 airtanks
6 air sources
at least 20 types of bbs , many hours of cleaning everything
eliminated the bounce back hammer,,,,,
and i will fill this page with other things
i know it can shoot like charm but why does not do it anymore ?

just to understand: my backyard neighbor has a apple tree, about 70 m. the apples where the targets, by 70m !, i was able to do 1 shoot - 1 kill last year, bbs where fling directly into .... now bbs goes all over the place .....
my neighbor does not live here anymore, so plenty of targets ................

i know i want airsoft to shoot like a pellet gun, but it can be done.......
come undone
PracticallySane
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Wed Dec 30, 2020 6:19 pm

This is the exact same gun from a year ago? But different performance? Did I get that correct? That is a curious issue for sure. The scientific method would say you must have changed a variable to change the performance. Is there anything different?
I’m a scientist; because I invent, transform, create, and destroy for a living, and when I don’t like something about the world, I change it. ~Rick Sanchez.
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mrfoo
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Thu Dec 31, 2020 2:43 am

PracticallySane wrote:
Wed Dec 30, 2020 6:19 pm
Is there anything different?
Quite a lot, going through the list above :)

I'm no expert on bbs, but something with a smoothbore barrel and no other "gizmo" to ensure reliable, repeatable spin of the bb is going to result in random or more-or-less random spin, and thus bbs wandering off anywhere they damn please. That holds for airgun pellets as well - without a rifled barrel, they start to tumble almost instantly they exit.

So my guess is that this is the determining factor :
no hop-up system
It's possible that the original iteration forced the loaded bb in such a way as to influence the random factors enough to impart a more or less repeatable spin, and subsequent tearing down / rebuilding has removed that. I'd try implementing a hop up or some other way of reliably forcing a repeatable spin on the bb.
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farcticox1
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Thu Dec 31, 2020 7:05 am

It's 2020, would you expect anything different, wait until next year at least.
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Thu Dec 31, 2020 7:07 am

Round balls do not use rifling. And shooting a round ball from a rifled barrel is horribly inaccurate.

And yes he mentioned things he changed trying to chase his performance, which was apparently gone before any thing was changed.

My only guess is gasses from the barrel are imparting spin on the bb when it leaves causing it to wonder.

A spining ball acts like a tire and will "climb" or "steer" through its flight path.

Google the magnus effect if you dont believe me.
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Thu Dec 31, 2020 7:30 am

To amend my previous statement.

I looked into airsoft and how the magnus effect pertains to accuracy.

Airsoft guns use a "hop-up" to impart back spin to the projectile. This gives it a desirable lift increasing range and accuracy.

However if you try to impart rotational energy the way rifling does to a bullet you will never hit the same space twice.

My apologies.
I’m a scientist; because I invent, transform, create, and destroy for a living, and when I don’t like something about the world, I change it. ~Rick Sanchez.
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mrfoo
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Thu Dec 31, 2020 8:47 am

I wasn't suggesting he should use a rifled barrel*, I thought that was fairly clear. What's important is imparting a known and consistent spin on the projectile such that the aerodynamic effects can be compensated for. A hop up does this by imparting backspin on the projectile, using the aerodynamic effect to impart lift (thus helpfully increasing range) as well as stabilising the trajectory. There's probably other ways of doing this (imparting a consistent spin) but the hop-up seems like a pretty good solution.

* although lead 'round' balls can, do, and have historically, benefitted from being fired through rifled barrels, it's bloody hard to do this with plastic bbs, mainly because it's hard to get a rifled barrel to impart a longitudinal spin on a hard sphere.
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Thu Dec 31, 2020 9:50 am

I dont think you actually Google the magnus effect? Its not the "aerodynamic" effect.

Lead balls where phased out and replaced with mini balls when rifling became common place.

I can agree to disagree, I would never use a rifled barrel for a spherical projectile. My 2.5 cents...
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Thu Dec 31, 2020 11:15 am

Hop-up spin is imparted by friction between the rubber bucking and the BB. This is by far the biggest variable in airsoft and the hardest to get consistent. Something seemingly irrelevant like the BB texture or humidity or lubrication can completely throw it off.

If I was looking for an accurate airsoft gun, I would eliminate the hop-up and instead use a laser rangefinder for accurate range estimation and a scope that can compensate accordingly.

I'm sure an arduino whiz could come up with a motorized scope mount that would take an input from a laser rangefinder and translate it into a change in scope elevation so it's immediately on target.

Worth noting that like rifling, the hop-up spin robs energy from the projectile so it means less energy retention at range.
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Thu Dec 31, 2020 11:28 am

PracticallySane wrote:
Thu Dec 31, 2020 9:50 am
I dont think you actually Google the magnus effect? Its not the "aerodynamic" effect.
It's absolutely aerodynamic, and I didn't need to google it. Higher education in physics will do that for you :) What would you suggest as a mechanism for the magnus effect other than aerodynamics? Unicorn farts, perhaps?

As for lead balls, there's a lot* of people still shooting round balls in rifled and unrifled muzzleloaders. It seems that the rifling for round balls is much less pronounced than that for the later minié balls, and, in turn, modern projectiles. I did need to google this, it wasn't covered. The trick, it seems (and again, this is from some google-fu) is packing the round ball in with a patch; this allows it to conform to the rifling and have spin imparted to it. Round balls are apparently also shot from revolvers (guess where I found this out?) but the the technique is different, a "ring" of the ball is removed by forcing it into a smaller diameter, this allows the ball itself to deform and take the form of the rifling.

Stay safe in the new year :)

* perhaps not that many, but still - well - enough that google could find them. I didn't try Bing.
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Thu Dec 31, 2020 11:49 am

Magnus effect has an affect on aerodynamics, it is not however aerodynamics. They are two separate things

When you rotate a wheel it moves, not because of aerodynamics but because it is displacing its self across the ground.

An airplane is aerodynamic. Cars are aerodynamic. Neither of which are rotating through the air.

The magnus effect is what we are describing...

I will concede though, it doesn't seem like you are worried about the proper science, rather that your opinion is fact.

https://en.m.wikipedia.org/wiki/Magnus_ ... 20spinning.

I love these forums, these guys are incredibly intelligent. Happy new year!
I’m a scientist; because I invent, transform, create, and destroy for a living, and when I don’t like something about the world, I change it. ~Rick Sanchez.
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Thu Dec 31, 2020 11:51 am

I do want to reiterate though. I mean no disrespect. 🙂
I’m a scientist; because I invent, transform, create, and destroy for a living, and when I don’t like something about the world, I change it. ~Rick Sanchez.
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jackssmirkingrevenge
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Thu Dec 31, 2020 11:53 am

Here's to ending 2020 on good terms and hoping that 2021 will not get too much worse before it gets better, cheers!
hectmarr wrote:You have to make many weapons, because this field is long and short life
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mrfoo
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Thu Dec 31, 2020 12:36 pm

PracticallySane wrote:
Thu Dec 31, 2020 11:49 am
I will concede though, it doesn't seem like you are worried about the proper science, rather that your opinion is fact.
PracticallySane wrote:
Thu Dec 31, 2020 11:51 am
I do want to reiterate though. I mean no disrespect.
Really. Because putting a smiley on the end makes it all so much more polite.

Happy new year.
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Thu Dec 31, 2020 12:51 pm

Doesn't it? 🙂

Text doesn't covey emotion or intent, without physically speaking with someone it is impossible to covey "tone"

Noticed i changed my point from "spin on a bb will degrade accuracy" to "the magnus effect has a positive affect on accuracy".

I gathered information, and changed my opinion because I was wrong...

So yes, no disrespect. aerodynamics and the magnus effect altho related are two separate physics properties.

🙂🙂
I’m a scientist; because I invent, transform, create, and destroy for a living, and when I don’t like something about the world, I change it. ~Rick Sanchez.
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