Scope Field Eval Explanation and Standards

[Bubblehide]

Just giving you shit on the "everyone is now dumber for having read that." Billy Madison reference.

No worries, I don't take things personally, besides, all of us humans make mistakes. It the ones that can't admit that that your statement applies to.

 

[TreeStandAthlete]

You know what, you're right, I don't know what I was thinking.

The heavier scope would hit the ground with more momentum though...I skipped too many physics classes to know what if any impact (pun intended) that would have on the damage to the scopes.

 

[Bubblehide]

The heavier scope would hit the ground with more momentum though...I skipped too many physics classes to know what if any impact (pun intended) that would have on the damage to the scopes.

Impact Force from Falling Object​

Even though the application of conservation of energy to a falling object allows us to predict its impact velocity and kinetic energy, we cannot predict its impact force without knowing how far it travels after impact.

If an object of mass m=kg is dropped from height h = m, then the velocity just before impact is v = m/s. The kinetic energy just before impact is equal to its gravitational potential energy at the height from which it was dropped: K.E. = J. But this alone does not permit us to calculate the force of impact! If in addition, we know that the distance traveled after impact is d =m, then the impact force may be calculated using the work-energy principle to be Average impact force = F = N.

Note that the above calculation of impact force is accurate only if the height h includes the stopping distance, since the process of penetration is further decreasing its gravitational potential energy.

The average impact force calculated here is the average over distance, which can be presumed to be proportional to, but not the same as, the average over time.

 

[Mike Islander]

Not fun when it happens to you Wacko, but everything can be broken.

Some things I've thought of since the first time I saw this Form...

The difference in impact force between a 10lb setup and a 20lb setup is 2x, all else being equal. There is a linear relationship between the weight and the impact force. This is pretty easy to account for, but if someone wanted to do this test independently and compare notes as accurately as possible, having the rifle weights be similar would be important.

Weight of the rifle has little effect in this case, except for the difference in rate of deceleration that two different weight rifles experience on a flexible impact surface. How significant that difference is, I know not.

For zero hold my take is that it's primarily internal components being tested. Deceleration movement, including movement to failure. In that case internal component weight is probably far less important than internal component/design stength, since strength to weight ratio is very high.

 

[Bubblehide]

Weight of the rifle has little effect in this case, except for the difference in rate of deceleration that two different weight rifles experience on a flexible impact surface. How significant that difference is, I know not.

For zero hold my take is that it's primarily internal components being tested. Deceleration movement, including movement to failure. In that case internal component weight is probably far less important than internal component/design stength, since strength to weight ratio is very high.

Take a look at this:

This right here may be something Form should film as a part of the inner-occular method and analysis. I'd place a camera at ground level to film the impact and one on a tripod to film him dropping the scoped rifle.

@Formidilosus

 

[Carl Ross]

For side impacts where presumably the rifle and optic could land at the same time, the rifle weight doesn't matter so much. For a top impact where the whole thing lands on the scope, it certainly does.

I certainly wasn't trying to muddy the waters here, just pointing out some variables to consider. This test doesn't need to be peer reviewed journal ready to be useful, and I absolutely think it is useful as is. Especially if Form is testing with the same rifle and using the same or similar ground.

 

[Bubblehide]

For side impacts where presumably the rifle and optic could land at the same time, the rifle weight doesn't matter so much. For a top impact where the whole thing lands on the scope, it certainly does.

I certainly wasn't trying to muddy the waters here, just pointing out some variables to consider. This test doesn't need to be peer reviewed journal ready to be useful, and I absolutely think it is useful as is. Especially if Form is testing with the same rifle and using the same or similar ground.

Agreed, but some have asked to see the video, I just posted so we all have a better understanding, and videoing the impact also, will help.

 

[ElPollo]

The average guy wants the clearest glass, everything else is a distant 2nd, 3rd, 4th, etc.

The only reason this is true is that gun gear reviewers don’t do what Form is doing. Who in their right mind would buy a scope that will lose zero from a boo-boo resulting from a 6” drop on a shooting mat? The point of a scope is to hit stuff, right?

 

[Mike Islander]

For side impacts where presumably the rifle and optic could land at the same time, the rifle weight doesn't matter so much. For a top impact where the whole thing lands on the scope, it certainly does.

I certainly wasn't trying to muddy the waters here, just pointing out some variables to consider. This test doesn't need to be peer reviewed journal ready to be useful, and I absolutely think it is useful as is. Especially if Form is testing with the same rifle and using the same or similar ground.

Top impact matters primarily for macro-deformation of the scope. My intuition (which could be utterly wrong) says that for these drop tests from relatively low heights, this is less important than internal components bending or breaking due to deceleration, as scope tubes in rings are pretty tough. I'll read and see if Form elucidates this.

 

[Formidilosus]

Top impact matters primarily for macro-deformation of the scope. My intuition (which could be utterly wrong) says that for these drop tests from relatively low heights, this is less important than internal components bending or breaking due to deceleration, as scope tubes in rings are pretty tough. I'll read and see if Form elucidates this.

I am not an engineer or designer. All I’m offering is what I’ve seen and some of what I think is happening.

First, it is common for the scope tube itself to bend. Maybe slight, sometimes not, but they do. Long, thin tubed scopes with large objectives are not kind to zero retention.

Second, shifts are generally in the direction of drop on the sides- left side drop cause POI to move left, right side to the right, top impacts cause POI to go high- not always, but mostly.

Third, some scope do it relatively consistently, some randomly- but it is not uncommon for a drop to cause a shift, then the next shot either moves back to POA or moves back closer.

 

[Deywalker]

I am not an engineer or designer. All I’m offering is what I’ve seen and some of what I think is happening.

First, it is common for the scope tube itself to bend. Maybe slight, sometimes not, but they do. Long, thin tubed scopes with large objectives are not kind to zero retention.

Second, shifts are generally in the direction of drop on the sides- left side drop cause POI to move left, right side to the right, top impacts cause POI to go high- not always, but mostly.

Third, some scope do it relatively consistently, some randomly- but it is not uncommon for a drop to cause a shift, then the next shot either moves back to POA or moves back closer.

Are red dot POI's ever shifted due to a drop? I would assume there wouldn't be with all the internals being electronic, but until recently I thought almost all expensive scopes worked reliably. I'm debating a SWFA 1-6 and an Aimpoint T2 for a 16" AR-15 and was curious if you had any notable failures.

 

[id_jon]

Are red dot POI's ever shifted due to a drop? I would assume there wouldn't be with all the internals being electronic, but until recently I thought almost all expensive scopes worked reliably. I'm debating a SWFA 1-6 and an Aimpoint T2 for a 16" AR-15 and was curious if you had any notable failures.

Check out Sage Dynamics on youtube, he's been drop testing for years now. Aimpoint T2 should be good to go.

Edit: it looks like he has not tested the Aimpoint T2 now that I look though...

 

[Formidilosus]

Are red dot POI's ever shifted due to a drop? I would assume there wouldn't be with all the internals being electronic, but until recently I thought almost all expensive scopes worked reliably. I'm debating a SWFA 1-6 and an Aimpoint T2 for a 16" AR-15 and was curious if you had any notable failures.

Yes. Most red dots suck. Aimpoint are the NF Milspecs of the red dot world.

 

[Deywalker]

Yes. Most red dots suck. Aimpoint are the NF Milspecs of the red dot world.

Any preference in the aimpoint line? I see a lot of recommendations for the T2 and almost nothing about the CompM5. for general use sub 300 would you rather have the 1-6 or the Aimpoint?

 

[Formidilosus]

Any preference in the aimpoint line? I see a lot of recommendations for the T2 and almost nothing about the CompM5. for general use sub 300 would you rather have the 1-6 or the Aimpoint?

Comp M5 or M5b for a rifle.

As for red dot versus LPVO- that’s all on use.

 

[Shraggs]

any experience with the MRO relative to the aim points above From ?

 

[Formidilosus]

any experience with the MRO relative to the aim points above From ?

Yes. The MRO isn’t true 1x, has fish eye, tend to have quite a bit of parallax, and a noticeable tint.

 

[Shraggs]

Thanks, impact robust similar to aim points ?

 

[Formidilosus]

Thanks, impact robust similar to aim points ?

They are relatively durable.

 

[BjornF16]

Actually, if you drop 2 objects the exact same shape and size, from the same exact distance from the ground, but one is heavier than the other, the heavier object will hit the ground first. Their acceleration rate, when dropped is different. So it is more than a 2x impact.

This is incorrect.

Acceleration is constant 32.2 ft/sec^2.

A 10 lb object dropped at same time and from same height will impact at the same time as 20 lb object. Basic physics.

Put a feather in vacuum chamber and drop it, will hit at the same time as a ball.

Edit: I see I am late to the game