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Old 12-26-2019, 08:42 AM   #1
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Over hop discussion

So I hear people talk about over hopping bbs and say they want the bb to travel straight as possible and as far as possible to the target and then start to fall off. But if someone was looking for realism wouldn't we want to over hop slightly to get the arc that an actual bullet does on it's way to the target? And wouldn't that over hop give us a little more range? Or does that over hop degrade accuracy and energy rather than having the bb fly as straight as possible before falling off? I've been airsofting a long time but I'm kinda new to building a sniper and the desired trajectory and ballistics of the bb.
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Old 12-26-2019, 09:14 AM   #2
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Just FYI, An actual bullet does not arc up at all. it continues to fall as soon as it comes out of the barrel. Now it can seem like that as most sight in their scope where to where it crosses the bullet path twice. For example, on my 30-06, zeroed at 75yards. It is zero again around 170yards. What this does for me, is I can put my crosshair on the bulls eye any distance from 50-200 yards and I know that I will be +-1" in elevation which is plenty precise enough for hunting coyotes without worrying about bullet drop and having full confidence in an ethical kill.
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Old 12-26-2019, 09:28 AM   #3
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Now I am not military or a long range competition shooter by any means so they may sight their weapons deferentially for different reasons/purpose.
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Old 12-26-2019, 01:33 PM   #4
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For longest range- overhop
For best accuracy- straight trajectory
For dropping bbs behind cover- underhop.
Basically, overhop allows you to have maximum range and also curve bbs sideways by tilting your gun. Also, if there is a gap at the bottom of a wall, you can curve a bb through the gap and up.
Straight trajectory is what Novritsch (and I use). It means that if you point your gun, you will hit, without any of this bloody lark with aiming high or low.
Underhop is quite popular. It allows you to drop a bb on someone. A good person to watch is Spider- on of the guys on the Novritsch channel. He has his gun set to drop at 60 metres so he can drop bbs on people by aiming up.
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Old 01-06-2020, 09:10 PM   #5
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Hmmm I'm pretty certain a bullet has an arc at long range. I'm not talking about your deer rifle that's sighted in for 100 yards
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Old 01-07-2020, 03:31 AM   #6
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No bb really goes straight to the target. Or at least at long range that does not happen.
Normally what I do is I have the bb shoot slightly below the target and then the hop kicks in and lifts it just about the target and then it falls again near the end (normally about 80-90 meters on a high powered rifle). The heavier the bb does normally help make the trajectory flatter though but you need the energy to get the bb to the target.
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Old 01-07-2020, 03:58 AM   #7
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Hmmm I'm pretty certain a bullet has an arc at long range. I'm not talking about your deer rifle that's sighted in for 100 yards
It does have an "arc" not because the spin creates and lift (unlike overhopping) but because the rifle is fired at an arc. Like throwing a football (american). You need to throw it pretty high to send it 50yards not because throwing a spiral pass creates lift, but because you need throw it that high to get it that far as it continually drops once it comes out of your hand. Even my "deer rifle" (which is a popular sniper rifle cartridge) has an "arc" in a way at 100-200yards. It drops something like 2-3 inches so if a bore sight was installed, to hit the bullseye with the bullet, the bore sight would be aiming 2-3 inches above the target. At super long ranges, say 1,000 yards, that bore sight would be aiming 25-30 feet high to hit the bullseye. This is probably what you are talking about as well. My point is that I don't think overhopping makes the flight path any more or even less realistic to a real steel rifle as the flight characteristics are so different any way (airsoft bb with any kind of backspin is creating lift opposed to a real bullet comes out of the barrel dropping). What I think does make it more realistic is if it aids the sniper (person) to make a better shot.
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Old 01-07-2020, 12:12 PM   #8
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That was what I was wondering though if giving the bb a bunch of arc in the trajectory makes it go farther with the same amount of accuracy.
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Old 01-07-2020, 03:04 PM   #9
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Quote:
Originally Posted by Sniperfitter View Post
So I hear people talk about over hopping bbs and say they want the bb to travel straight as possible and as far as possible to the target and then start to fall off. But if someone was looking for realism wouldn't we want to over hop slightly to get the arc that an actual bullet does on it's way to the target? And wouldn't that over hop give us a little more range? Or does that over hop degrade accuracy and energy rather than having the bb fly as straight as possible before falling off? I've been airsofting a long time but I'm kinda new to building a sniper and the desired trajectory and ballistics of the bb.
Basically you're exactly right on track up to "does that over hop degrade accuracy", where there really isn't any hard evidence saying it does or doesn't- we don't know.
I wonder...the above may have some wacky caveat like "actually with enough backspin, the BB could indeed waste energy climbing, resulting in reduced range compared to optimal backspin fired at the same angle"- but I highly doubt that, and even if it's technically true it isn't relevant- it's not something you'd actually run into because setting your hop up to raise the BB 50 feet in the air is...well it's absurd, obviously, haha.

Back to this...
Quote:
Originally Posted by Sniperfitter View Post
That was what I was wondering though if giving the bb a bunch of arc in the trajectory makes it go farther with the same amount of accuracy.
In my opinion, I believe it would indeed have the same accuracy, or any change would be negligible. In fact I feel like you could prove this to be true regarding at least one factor of accuracy with logic alone:

Let's define hop-accuracy as the angle size which, centered pointing straight up in the air looking down the muzzle, describes the BB's trajectory on the plane of left/right/up/down; so flawless hop-accuracy means when you look through the scope, all BBs [hopped slightly above flat] will travel ONLY along the central vertical crosshair.

Perform two tests:
A) Tune hop-up to create a flat trajectory; observe hop-accuracy (if trajectory is flat, technically you cannot observe it when aiming flat; if you angle the rifle slightly up at different vertical vertical angles, you should be able to see hop-accuracy, and confirm it doesn't change)
B) Tune hop-up to a reasonable over-hop trajectory; observe hop-accuracy

I believe A and B should show the same hop-accuracy, so I feel like we can say hop-accuracy wouldn't change- though there are other factors to consider (maybe bucking material has a specific amount of compression which results in the most consistent distribution of pressure across the BB- meaning more or less pressure would mean decreased 'buck-accuracy', etc...).

I just don't get the feeling any factor influencing accuracy would change significantly with hop-up tuned within reason.
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Old 01-09-2020, 08:21 AM   #10
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Quote:
That was what I was wondering though if giving the bb a bunch of arc in the trajectory makes it go farther with the same amount of accuracy.
Gotcha, sorry I misunderstood you. It would be neat to specific testing on this. With my basic knowledge of physics and other real world evidence applying a lot of over hop would not give you more range. I know I am over simplifying this but the magnus effect works perpendicular to the bb flight. So if the bb is traveling horizontal, the backspin is applying a vertical force. When that bb starts to rise because of back spin over takes gravity or launch angle is increased, it is now going "Y"degrees up from horizontal and now the back spin is a force "Y" degrees back from vertical. Then you have force working against the X component of your initial velocity. At some point, given enough spin or launch angle, the bb can even go "backwards" in the "X" direction (like fire straight up) from its furthest traveled distance "X". My theory is to get the longest range (not necessarily the most practical for most snipers which is why I don't do it) is to apply just enough back spin to stabilize the shot thru out it entire path (I would love to know more about spin decay and see/do some studies on it) and launch it at higher angle (I would guess 20-30deg). Consider these scenarios.
1. Driving a golf ball (something I have had a fair amount of personal experience with)- To get the most carry, you want to minimize backspin and hit it high. To do this you use a lower loft driver 9.5-8deg and swing up on the ball. Now the difference here is the length of your longest hit (in controlled environment with same equipment) is determined by how much energy he/she can produce and how efficiently it can be applied to the ball. In airsoft efficiency really doesn't affect range that much, just our bolt pull or gas power consumption so some of this is less important but I think some principles can be applied to airsoft.
2. Put .12g bbs in your rifle see what it takes to fire them the furthest.
3. Lee Wade+Hunteerng fireing airsoft bbs absurdly long distances with gas rifles (somthing like 150-170 yards or something) if I remember right, seems to not have a lot of hop but use custom adjustable angle scope riser.

Any of you physics experts got any thoughts/critiques here?

Like Majic said, there isn't a lot of hard evidence on this and I don't have any either. As a matter of fact, I even like to slighty over hop my bb.s, not to get the most range but to get the most range with out overhold (kinda like my 30-06 example).

I too feel like the accuracy should not be significantly different between a flat shot and a overhopped shot accept for user error in canting the rifle (amazing how much I do this lol) in which the over hopped shot would deviate more.

This would be a cool study in a large non drafty warehouse (if that even exists lol).
1. Airsoft rifle in vise chonoing at X velocity with Y weight bbs. Small hop pressure applied (underhopped) shot and range measure at 0, 10, 20, 30, and 40deg
2. Airsoft rifle in vise chonoing at X velocity with Y weight bbs. Medium hop pressure applied (Flat trajectory) shot and range measure at 0, 10, 20, 30, and 40deg
3. Airsoft rifle in vise chonoing at X velocity with Y weight bbs. More hop pressure applied (5ft overhopped) shot and range measure at 0, 10, 20, 30, and 40deg
Then based on what gives the most range test, keep testing.
Sounds like a cool summer project. I got too many of those now and no access to a large enough warehouse. Now I am planning on making an adjustable angle scope riser and just doing some observational testing this coming summer/fall.

Cool discussion btw sniperfitter
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Old 01-09-2020, 09:50 AM   #11
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I personally find flat flight is easier to compensate for at distance.

The other assumption many make is that the overhop is applied perfectly each time. That is rarely the case. I find that off angle installations of nubs, rubbers, etc are more pronounced the more you apply hop up. A right side shot bias that wasn't present at flat hop settings may suddenly appear when overhop is applied. Additionally, there's the variable of bb placement being the same shot to shot also effecting whether the hop is applied consistently each time.

Anyway, my point is that I find flat flight hop settings to produce more accurate results. I won't delve into range increases (if they exist) with overhop applied, but in my experience adding overhop makes the rifle less accurate (or at the very least harder to compensate for) at distance.
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Old 01-09-2020, 12:10 PM   #12
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Quote:
I personally find flat flight is easier to compensate for at distance.

The other assumption many make is that the overhop is applied perfectly each time. That is rarely the case. I find that off angle installations of nubs, rubbers, etc are more pronounced the more you apply hop up. A right side shot bias that wasn't present at flat hop settings may suddenly appear when overhop is applied. Additionally, there's the variable of bb placement being the same shot to shot also effecting whether the hop is applied consistently each time.

Anyway, my point is that I find flat flight hop settings to produce more accurate results. I won't delve into range increases (if they exist) with overhop applied, but in my experience adding overhop makes the rifle less accurate (or at the very least harder to compensate for) at distance
You have some good points.
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Old 01-09-2020, 01:11 PM   #13
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Originally Posted by Jbrinker1 View Post
I know I am over simplifying this but the magnus effect works perpendicular to the bb flight. So if the bb is traveling horizontal, the backspin is applying a vertical force. When that bb starts to rise because of back spin over takes gravity or launch angle is increased, it is now going "Y"degrees up from horizontal and now the back spin is a force "Y" degrees back from vertical. Then you have force working against the X component of your initial velocity. At some point, given enough spin or launch angle, the bb can even go "backwards" in the "X" direction (like fire straight up) from its furthest traveled distance "X".
You bring up a great point here- this is what was subconsciously guiding my previous post mentioning sub-optimal range due to hop, but I couldn't figure out why I felt that way :P this is it!
But...
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Originally Posted by Jbrinker1 View Post
My theory is to get the longest range (not necessarily the most practical for most snipers which is why I don't do it) is to apply just enough back spin to stabilize the shot thru out it entire path (I would love to know more about spin decay and see/do some studies on it) and launch it at higher angle (I would guess 20-30deg).
I may be misunderstanding and we may agree here, but if we're involving angle, I believe maximum range would be attained by angling the rifle at 45 degrees, and tuning hop-up through the scope to travel "flat" down the center of the crosshair (so, not actually flat / parallel with the Earth (lmao guess I'm a flat Earther now- you know what I mean...)). If you tuned hop-up to be flat, shooting flat, then angled the rifle up, you would get that effect you outlined, with the Magnus Effect working slightly backwards towards the shooter as opposed to directly away from the ground / straight up.
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Old 01-10-2020, 09:34 AM   #14
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I may be misunderstanding and we may agree here, but if we're involving angle, I believe maximum range would be attained by angling the rifle at 45 degrees, and tuning hop-up through the scope to travel "flat" down the center of the crosshair (so, not actually flat / parallel with the Earth (lmao I think I just implied the Earth is flat- you know what I mean!)). If you tuned hop-up to be flat, shooting flat, then angled the rifle up, you would get that effect you outlined, with the Magnus Effect working slightly backwards towards the shooter as opposed to directly away from the ground / straight up.
Yep yep, we are on the same track. And no problem on the asumptions/ implications (I am an engineer, we do that a lot to make the math easier and multiply by 4x and add FOS lol!).In a perfect world on paper for a simple projectile motion, it works out that max range is achieved with 45deg launch angle. Adding in the magnus effect, assuming it's force is perpendicular to the differential of the flight curve, it would like you said be acting backwards towards the shooter and up. Back spin would also would increase the average climb angle from 45deg to something more. If I do one of my handy simplifications, If I graph bb path and draw a line from launch point to peak, I think to get the most theoretical range, this line would need to be 45deg with max initial velocity and any backspin is going to work against initial velocity and raise that 45deg. That is why I think it would be something less than 45 deg. Doing the calculus with magnus effect and spin decay is a league above my math expertise (maybe a few league lol). I would love to see it though! I may try to work out a simpler equation just for fun. Here is what I am thinking to simplify it.
1. Figure out the max range X of Z weight bb with air restriction at Y initial velocity and neglect magnus effect and the time T it take to travel that distance.
2. Take that max X range and time T and see if I can find a simple equation for the amount of initial spin to have 0 spin at the end of T (we don't want that bb to stop spinning before the end of it's flight and have it destabilize (knuckle ball) near the end of it's range).
3. Take that spin rate and divide by 2 to get the average (assuming spin decay is linear) and see what the magnus force is and add it's components to the max range plot and decrease launch angle until the line from peak to start point is still at 45deg.

I am too far off all you calculus physics experts? I know it is not going to come out right in the real world but would be really interesting and give us a good idea. Maybe open our eyes to a new way of sniping like sniperfitter is sugesting (more realistic but exaggerated to accommodate our low power+light projectile limits we face in airsoft).

If my theory is correct, in a realistic airsoft situation for max range of lobbing bb.s as accurately as possible at still objects, would probably be limited by the height of your optic to be able to sight over muzzle at target for the large launch angles (a 14" scope riser to see over a 20" barrel at 45deg just isn't going to happen). Also you can trow at reliably hitting some one as the time to target would be so much that the target probably moved and external factors with that amount of time would most likely take it off course enough to miss. With that thought, to get back down to earth, the simplest/best way to figure this out is to start with the max reasonable scope riser then figure max launch angle and like majic was sugesting tune hop up to flat at that launch angle then test different hop setting and checking max range (definatly going to try this even if I don't get to the math....wich I probably won't). Lets say 6" is reasonable for a scope riser. Then 17.75deg would be our max launch angle and tune hop up for max range with that set up. If our riser was adjustable then ranges could be tested for different launch angle settings and if you have a spotter to laser ranges, elevations, and wind speed.... to me it would be more realistic to how I believe real super long range sniping happens.
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Old 01-10-2020, 10:01 AM   #15
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Another quick thought is maybe spin decay might be our limiting factor. I don't suspect that it would but very well could be. If an expert can chime in here that would be awesome. Here is my thinking, if we need a ton of spin to maintain at least a little back spin to stabilize bb thru out it's entire potential range, the launch angle to achieve max flight might be lower than we think (maybe it is close to horizontal like most shoot anyway). Then we would again have three max ranges. #1 max range (bb with no spin near the end of it's flight causing "knuckle ball effect"). #2 Max precise range (bb maintains some backspin till the very end of it's flight). #3 Max effective range (bb hits target 8-9:10 with acceptable time-to-target).

I don't think range #2 would be unusable in air soft either. I have had plenty of times where a group of is standing in/near their fort just talking/planning and a precise and accurate "artillery" shot would have got one and broke up the meeting as time to target isn't an issue (I have done it a few times just free hand "no sighting" and was successful a couple of those times. What sniper can't resist trying this? lol). Also, similar scenario, different strategy that I have used is if you can just hit the fort/cover they are in to keep them afraid and heads down where they can't spot you and don't know they are out of your "effective range", it lets you "assault" teammates to take better positions. Maybe range #1 might be precise enough for this scenario as well.

I will quit rambling...I love thinking like this. I want to learn more and hear other thoughts critiques, theories, and experiences. Again neat topic and I am not sure if the "max airsoft sniper rifle range" has been approached like this (max range and realistic possible) before.

Last edited by Jbrinker1; 01-10-2020 at 10:05 AM.
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