Pellet speed H&N 5.5mm

[Caliber 22]

If you can, measure the velocities with a chrony at several different ranges

That is what I was thinking about. BUT, I don't have a chrony to measure at different ranges. The one I have slip over the end of the barrel and the pellet is going through it. And I don't know anybody with a full size or radar chronograph. I did ask around at the dealers and shooting range but either they don't want to give me the names or they really don't know who has one.

 

[JungleShooter]

I don't know anybody with a full size of radar chronograph.

● You won't need a radar chrony. So far I have been using a simple Caldwell ballistics chrono.
Buying one with a light kit is worth the extra cash. At night there is less wind in my coastal desert corner of the globe.
Similar types: ▪Competition Electronics Pro | ▪Shooting Chrony

● Put a thick acrylic glass before the breakable sections of the chrony, because a chrony-cide is unlawful.

● Measure the distances several times to make sure they're correct.

● Make sure you keep the pressure in your gun within the range where you have the least variation in muzzle velocities.

● Do record the meteorological conditions, and use for your calculations.



I'm just repeating what I have learned on the forums....
Great place to learn.

Matthias

 

[Caliber 22]

I did try MERO with the GA and GA2 model from Miles. Also the G1 and GA in MERO as well as in Strelok but this pellet has its own idea of BC and flight curve.

Buying one with a light kit is worth the extra cash.

I would like to but it is a bit more expensive than what I can afford right now for using a few times and then collecting dust.

The rest I agree with.

 

[Caliber 22]

On Strelok website Igor say "Can calculate trajectory without using ballistic coefficient!".

How can I do that ?

 

[JungleShooter]

On Strelok website Igor say "Can calculate trajectory without using ballistic coefficient!".

How can I do that ?

Using trajectory validation:
On the main screen with the 8 buttons on the bottom ➔ bottom row ➔ far right button (with target and double arrow).

On the trajectory validation screen you select BC, and enter your MV, and the drop at a distance far, far beyond your zero range.

Strelok will give you a single BC number, using the drag model you selected when setting up your "bullet".


However, you observe that your particular pellet does not seem to follow the standard drag model of GA — especially at high velocities.
➔ So, this trajectory validation only works to the range that you "validated" the trajectory, other ranges will be off as you have observed.

➠ So, it seems like you're on for shooting groups at different ranges, and then tweaking Strelok, either adapting via trial and error 5 custom BC values, or a full custom drag model.
I think it can be done. (But don't be fooled by my confidence, I'm pretty ignorant. ➔ Miles/ Ballisticboy is the man. )


Matthias

 

[Ballisticboy]

It sounds to me as if the pellet in question has a steeper drag rise than the GA profile, which would seem correct looking at the pellet pictures shown in the thread. It is possible that the wadcutter drag profile may fit it better, though that one might be too steep a drag rise.

A purpose drag law could be created from the BC values at the different ranges by getting the form factors and thus the drag coefficient but, it is a fairly long-drawn-out process and needs a bit of imagination as to what is likely or unlikely. There is also the danger that the calculated values are based on measured drop which is the least accurate method, the reason being that there are a number of other things which can effect drop. The most accurate method with one chrono is by measuring MV and time of flight, possibly with one microphone and a laptop, though it would be difficult at the long ranges. Even with the time of flight and the MV, it may still be difficult if the reference drag laws are not the correct shape.

 

[Caliber 22]

Like most manufacturers they have a sketch and not a photograph in the picture of the pellet, that may be to have it look better than it is when the picture is resized. The person doing that sketch was not good in replicating the shape and dimensions, not good at all. Here is a photograph of a actual pellet I took from the tin, it looks way different than the sketch.

I don't know if the pellet is start spiraling at further distances and that for the few shots I did with it so far I was just lucky that it hit the target at the same position of the spiral. Is that possible? Maybe possible but is is probable? A high definition scope cam and Lab radar would come in handy now. For now the wind is vary still and should not have to much of an influence.

I think on this one I must at first forget the app and do a manual DOPE with a graph I can do on CAD to smooth out the curve and work from that. For now anyway until I can sort out the app data. Looking at what I see I will have to start at 50 meter and shoot at distances every 5 meter or even less to record where the changes take place. Sounds to me like a lot of shooting and measuring and walking back and forth moving the target. I do have a laser distance meter from Hilti that is certified 1mm accurate at 100 meter and can go up to 200 meter in good conditions. This is not a range finder.

 

[JungleShooter]

The Rifle Premium Round weigh 18.67gr. They state a 0.025BC.

Comparing your actual photo of the Rifle Round with the following... — might that be the same pellet — rebranded?

The Crosman Domed Ultra Heavy weigh 19.00gr.
The BCs that were measured by different shooters were mostly disappointingly low for such a heavy pellet:
▪ 0.017BC | MV 898fps | Range 30y
(by HAM)
▪ 0.021BC | MV 860fps | Range 5–83y
▪ 0.031BC | MV 750fps to 650fps | Range 25y

(Note: All these were calculated using ChairGun and GA.)


This pellet seems to behave more like a wadcutter than a dome....: The higher the velocity, the higher the drag (or, the lower the "apparent BC").
Maybe that's why you see such a weird trajectory — the GA standard projectile does not work for this shape at higher velocities....

Matthias

 

[Caliber 22]

might that be the same pellet — rebranded?

You might be correct. I never saw the Crosman 5.5mm pellets. They are not often on the shelves here. Whoever is importing it does not bring in huge quantities or very often.

 

[Caliber 22]

This morning the air is fairly still but the humidity is higher than before. The Rifle Round pellets behave much deferent than the previous shooting sessions, it is as if it rides on the dense air and don't drop as fast. ((Model aeroplanes also sits better in the air in the same conditions and glide much further with the same trimmings.) At best the groups are not as tight as the H&N and H&N are much more consistent in different conditions than the Rifle pellets.

Does Crosman pellets behave the same?

 

[Ballisticboy]

This morning the air is fairly still but the humidity is higher than before. The Rifle Round pellets behave much deferent than the previous shooting sessions, it is as if it rides on the dense air and don't drop as fast. ((Model aeroplanes also sits better in the air in the same conditions and glide much further with the same trimmings.) At best the groups are not as tight as the H&N and H&N are much more consistent in different conditions than the Rifle pellets.

Does Crosman pellets behave the same?

A minor point, but humid air is less dense than dry air, so the drag force will be slightly less as a result.

 

[Caliber 22]

A minor point, but humid air is less dense than dry air, so the drag force will be slightly less as a result.

Then it must have a much bigger influence on drag for this pellet than for others.

Either way, I don't think this pellet is any good for distances longer than 75 meter. Yes it is stated on their website that the max distance is 50 meter but H&N say the same on their website.