Some LabRadar Data from Nick Nielsen

[nielsenammo]

That's a ton of work.  I will get you some more data when I get my Labradar back, probably about 10 days or so

[rsterne]

I worked on the .50 cal 209 gr. EPP-UG data this morning, and here are the results....



Above is the data for the 6 shots that were within +- 1% of the average velocity at the muzzle and 100 yards (6 of 9 shots).... You will note that they are in two separate groups as to Cd and the shape of the curve.... no idea why.... Below is the nearly 1400 data points and the average Cd curve trendline drawn through them by Excel....



The BC for this bullet is actually quite low.... Although the SD is 0.12, the BC(G1) only averages 0.048.... when corrected to sea level from the 2100' altitude where the testing was done....

Bob

[nielsenammo]

I don't think I expected much different in BC from an EPP slug.  These bullets are good because they are pretty forgiving in most guns and shoot better than roundball.  The advantage of this round is if your gun does not have the power to push heavy long slugs or have a hard time finding a slug that is accurate these are a pretty good choice.  Will have to do some testing on a diabolo in the same weight/caliber as an EPP and see the BC difference.

[nielsenammo]

I cross checked this BC number with JBM Ballistics using shot no 1 raw data.

Using near velocity of 795 and far 736 with 85 feet between the points, and checking Std. Atmos at altitude it calculated 0.046 BC.

Seems pretty close.

[rsterne]

Here is the next set of data, one I'm sure will interest Nick in particular.... This is for his very own 34 gr. slug in .25 cal.... and it's a dandy.... The BC(G1) averages out to 0.094 over 100 yards.... Incidently, I used data out to 100 yards, even though there were a couple of data points where the S/N ratio was <10 before that....



All shots were within 1% at the muzzle, but the LabRadar lost tracking on one shot, so I omitted it.... You will note that Shot #2 has some weird data, so I excluded it when I did the average Cd.... There were a total of over 800 data points contributing to the trendline in the graph below....



The drag of this bullet is very flat over the velocity range tested.... and the bullet only loses about 120 fps over 100 yards.... If this bullet is accurate in your quarterbore, it will hit HARD with a lot of retained energy.... When I double checked the BC(G1) using ChairGun, I got 0.089 over 100 yards.... excellent for a bullet with an SD of just 0.078.... showing it has a Form Factor of less than 1.00.... better than the G1 Model at the 825 fps average velocity tested....

Bob

[nielsenammo]

Thanks for posting that Bob.  Bob told me in an email that this takes him 3 hours for each bullet.  That's a ton of work and I appreciate the effort.

This bullet is a hard hitting slug and has great accuracy in my Cricket and Marauders.

[rsterne]

Most of the time is inputting the data, getting the trendline for Distance, and then taking the Derivatives to get the Velocity and Acceleration.... The velocity data that the LabRadar outputs is simply way too jagged to allow computing the Cd curves.... Although they state an accuracy of 0.1%, that is 1 fps at 1000, and if one data point is low and the next high, you can get adjacent velocities that cross over.... the following one is higher than the preceeding one, which of course is impossible.... The curve fitting and taking Derivatives is time consuming, but the quality of the data is worth it, IMO....

I think the method for averaging the Cd I am using is great for multiple shots.... I think I can use the same method for stitching together different velocity ranges as well, to stretch out the data from, say 500 fps to Mach 1 or beyond.... That is something I am really looking forward to trying, when I get some data that starts Supersonic.... I have a couple of PCPs that can reach 1200-1300+ fps with pellets, and look forward to seeing how quickly they fall Subsonic....

Bob

[rsterne]

Here is the data for Nick's 39 gr. .25 cal slug.... Once again, I used 100 yards of data, even though there were a couple of points with a S/N ratio of <10....



Nick shot 10 shots, a couple didn't track too great, and two had some gaps in the data, so I picked the best 6 to plot.... There are over 1000 data points in the average Cd below....



Once again, the Cd is very constant over this velocity range.... This bullet has slightly higher drag than the lighter one, but since the SD is heavier, the BC is virtually unchanged at 0.092.... so with an SD of 0.089, the FF is just under 1.00.... This bullet only lost about 100-110 fps over 100 yards, so again will have very high retained FPE....

One thing you can notice in the data for the two NSA slugs is the few missed data points as the bullet goes downrange.... If you look at the graphs that show the average Cd, the grey dots are each data point.... Towards the left (lower velocity), you will notice a few gaps in the data where the LabRadar lost momentary contact.... This seems to start at around 80-85 yards in .25 cal.... but there is usable data out to 100 yards and beyond.... The more missed datapoints, the further the Cd plot seems to be from the average, which I think reflects on the quality of the data once the S/N ratio starts to drop under ~10, and the unit starts missing returns....

Bob

[rsterne]

These last two bullets show exactly why using a Drag Model that is different than your bullet doesn't give the correct results for the BC.... They have nearly identical Cd curves, in fact the 34 gr. is almost an extension of the curve for the 39 gr.... They both have a slight downward trend at higher velocity, the opposite of the G1 Model in that velocity range.... So, when you compare them to the G1, the faster bullet looks better compared to the slower one, because you are comparing it to a model that has more drag at higher velocities.... If you use a constant Cd drag model, then the heavier bullet ends up with a better BC than the lighter one.... Here is the G1 Drag Curve....



What really matters, in comparing them for wind drift is the ACTUAL Cd, anyway, divided into the SD.... When we do that, the lighter bullet returns a value of 0.409, while the heavier one works out to 0.414.... so the heavier will have marginally better performance in wind.... One other interesting fact.... These bullets both have a Meplat, and just as predicted by the McDrag program, they actually have a lower Cd than the G1 model at 750-900 fps....

Bob

[HectorMedina]

With all due respect Bob, Ron and Nick;

While I understand the desire to glean info and insights, are we justified in believing data that is beyond the instrument's capabilities?

Remember that radar works on the principle of a bounceback of an electromagnetic beam. It is logical then that the "footprint" of the BASE of the bullet/projectile MUST count for the maximum range where data is believable.

Trying to measure the 75 yards velocity of a 0.177" pellet must be like locating a B2.

Are you SURE that for 0.25" cal (as explored in this thread) the believable range is out to 100 yards?

Just curious.

Keep well and shoot straight!








Héctor Medina

[nielsenammo]

Out to 75 yards with the .25 was pretty consistent.  The 100 yard data was spotty so the ones that fell out of the norm were not used.  Most of the data was ~<10 fps of the average for a given range.  This is a regulated gun but even muzzle velocity over a chrony does not give the same value each time plus you have wind and environmental factors playing into the bullet's flight so with all that considered I think this data is pretty reliable.

Here are the raw numbers from the 39 grain JSB's at muzzle and different yardages fired from my Cricket.  Blanks are deleted values that recorded out of the norm.

Muzzle   10   25   50   75   100
               
795      774   743   697   659   625
800           777   745   695   654   617
796           775   745   701   664   632
805           780   747   697   655   
796           776   745   700   661   628
812           786   752   701   657   
803           775   743   698   660   626
793           772   741   695   657   622
               
800       777   745   698   658   625
               
6.4           4.4   3.3   2.4   3.3   5.1

[rkr]

Thanks for posting that Bob.  Bob told me in an email that this takes him 3 hours for each bullet.  That's a ton of work and I appreciate the effort.

This bullet is a hard hitting slug and has great accuracy in my Cricket and Marauders.

Those are choked barrels, what kind of accuracy are you getting? Sub MOA at 100Y?

[nielsenammo]

I mainly have shot these slugs in my Cricket and close range both JSB and my slugs are very accurate but JSB is slightly more accurate say out to 50 yards.  By 100 yards my slugs are more accurate and have way less drop.  Zeroed at 50 yards with a 25.4 JSB, my 34 grain slug hits higher on paper (less drop) than the JSB which almost 9 grains lighter.  The BC difference is incredible.

So even if the slug is too heavy if it were a diabolo pellet, because of the much improved BC it will have a similar or even better trajectory. As far a sub MOA, the Cricket can shoot sub MOA with this slug and the Marauder can shoot it very well but that gun is not as accurate as the Cricket to start so not sure if it would be sub MOA in a Marauder but should be very accurate.

This bullet has been tested in .250 barrels with 18 twists and faster with great results.

[rsterne]

Hector, if you look at the graphs showing the averages, you will see individual dots (in grey) where there are echos picked up by the LabRadar.... If you look back at the first post in this thread, you can compared the velocity data to the distance data.... You will note that the velocity data is not consistent enough to give accurate results without using a trendline, but the distance data produces a nice smooth plot.... By using a trendline from Excel (curve fitting) to smooth the data, you can fill in the gaps in the distance data.... By using this method, you no longer have to rely on the velocity swings, because you can calculate the velocity between returns (which are every 0.002 sec.), and from that the deceleration of the pellet as it moves downrange....

I do agree that there is an obvious limit to the range, and the smaller the caliber, the less distance you will be able to use reliably.... So far, we have only worked with .25 and .50 cal, and the .25 cal Kings provide a Signal to Noise ratio of greater than 10, with hardly any missed returns, out to 80-85 yards.... Nick's .25 cal slugs, which have a flat base, only dropped the odd echo out to 100-110 yards.... The .50 cal had good data out even further.... You can see where the data starts to diverge, and you can see where there starts to be a significant number of missed returns.... so it just becomes a matter of deciding how far out you can trust the information....

I hope that eventually we will have enough data, at enough velocities, to "stitch together" good data and be able to obtain a complete, and accurate drag model for many pellets and bullets.... It is a work in progress....

Bob

[nielsenammo]

I am happy to share data so we can all learn. I have ordered a BBT 357 design that should be completed this week and receive next.  I am sure Bob would like to get some data for that bullet so I will shoot it when I get the mold and my Labradar back.  Hopefully next week.

I can shoot more data points if you think it would help too Bob.  This data was just getting my feet wet and seeing what the Labradar could pick up.  I want to shoot it in my Recluse and my Bulldog to see how the BC calculates in two different guns.

[HectorMedina]

Hector, if you look at the graphs showing the averages, you will see individual dots (in grey) where there are echos picked up by the LabRadar.... If you look back at the first post in this thread, you can compared the velocity data to the distance data.... You will note that the velocity data is not consistent enough to give accurate results without using a trendline, but the distance data produces a nice smooth plot.... By using a trendline from Excel (curve fitting) to smooth the data, you can fill in the gaps in the distance data.... By using this method, you no longer have to rely on the velocity swings, because you can calculate the velocity between returns (which are every 0.002 sec.), and from that the deceleration of the pellet as it moves downrange....
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Bob

Yes, Bob. I have followed the thread and understand the reason to prefer distance data over velocity data, but I still think we are trying too hard to fit reality into a mould.

Of course reality has no "jumps" (not in our Newtonian world anyway), but I still thought it was too much work to come out with a result that is, for all practical purposes, "synthetic".

So, I looked into the LabRadar website and found this:

"What range performance can one expect with LabRadar?
In general LabRadar will typically measure the velocity of a 7.62 mm projectile from muzzle up to 100 yards. After extensive testing of a variety of calibers you can expect to obtain velocities at these distances when in the Standard Power Mode. Low Power setting will have about 30% less tracking*.
.177 Pellet - 30 yards;
.177 BB - 30 yards;
22 LR - 60 yards;
223 - 60 yards;
270 - 70 yards;
308 - 80 to 100 yards;
9mm - 130 yards;
40 S&W - 130 yards;
45 ACP - 130 yards;
500 S&W - 130 yards;
12 gauge Slug - 90 yards;
Paint Ball - 50 yards;
Arrows - 50 yards;
* Since every bullet has a different profile your results may vary. In general, the larger the base (excluding the boat tail) the great the distance the projectile can be acquired."


At the point we are, not only is it a question of getting a reading, but of getting a trustworthy reading.
Until that happens I will put my efforts into a kinematic approach to trajectories.
We shoot 0.177" pellets routinely out to 55 yards, sometimes 75.
Using the impact data to derive the trajectory has proven far more useful than trying to get drag and ballistic coefficients.

JMHO and of no great consequence. I'll get out of your hair now. Sorry!

Keep well and shoot straight!





Héctor Medina

[rsterne]

Nick, eventually I would like to get data at various velocities, so that I can "stitch" together the data.... For example, I have a couple of PCPs that can launch JSB Kings at over 1200 fps, and since the pellet will slow so quickly that data, well within the range of the LabRadar, will fill out the top end of the velocity range, as we already have good data up to about 950 fps.... and down to about 700ish.... So we need some shots starting at around 750, and assuming those will give data down to about 600ish, then another set at 650ish, to get us down to around 500.... We need a small overlap in the data, to allow selecting the optimum point for joining it, of course....

Hector, you are never a bother.... I always welcome your opinions and wealth of experience.... Just looking at the area of the base of the projectile, we would expect the LabRadar to lose contact with a .177 cal at half the range of a .25 cal.... while a .308 might do 50% more.... and a .357 double.... or about 4 times that of a .177.... Now that we have seen what the outputs of the datastream from the LabRadar look like.... and realize that their claimed 0.1% accuracy will cause velocities to overlap on occasion, even at relatively close ranges.... I think the "Doppler" effect is not accurate enough to give datapoints every 1/2 yard that are really usable.... so it makes sense to just use the Distance data.... and it is quite amazing how far away the unit can actually track a pellet or bullet....

Bob

[rkr]

I mainly have shot these slugs in my Cricket and close range both JSB and my slugs are very accurate but JSB is slightly more accurate say out to 50 yards.  By 100 yards my slugs are more accurate and have way less drop.  Zeroed at 50 yards with a 25.4 JSB, my 34 grain slug hits higher on paper (less drop) than the JSB which almost 9 grains lighter.  The BC difference is incredible.

So even if the slug is too heavy if it were a diabolo pellet, because of the much improved BC it will have a similar or even better trajectory. As far a sub MOA, the Cricket can shoot sub MOA with this slug and the Marauder can shoot it very well but that gun is not as accurate as the Cricket to start so not sure if it would be sub MOA in a Marauder but should be very accurate.

This bullet has been tested in .250 barrels with 18 twists and faster with great results.

I was wondering if they would work on my 100M BR .25 BSA. I've heard that slugs and choked barrels are no go but this seems not to be the case with your hollow design? We have a 200M BR coming for this season so I could use the improved BC.

Some results for .35 JSBs and .357 BBTs would also be very interesting.

[nielsenammo]

If your barrel is .250 and a fast twist rate >19 or 18 it should fly great.  The hard part about making slugs for airguns is there is no standard like there is with firearms.  .25 caliber can be .249, .250, .251, .252, .253 or .254 and I have way to know what you have.  I wish the industry could adopt standards so moving forward we could make better ammo.

I sold some 39 grain .250 slugs to someone who is not getting good results in his GM barrel in a Marauder.  I used the same slug in a GM barrel in a Marauder with great results.  He says his slugs are going in with almost no resistance and the one I used it was pretty tight.  Goes to show we can not rely on the manufactures to produce the same sizes and each gun may have to slugged or take your chance it is the same as the last guys.

I think the reason this bullet works in choked barrels is the rifle engagement is only on the back of the bullet and very little actually touches the rifling so they fly through the choke without much trouble.  I have a cast version of this bullet being made, in fact it is being cut today.  After it is cut they have to make the HP conversion so I am hoping to get it end of next week or soon after.  If it shoots well I will order the 5 matching molds and the price point will be significantly lower than a swaged version.

I have BBT .357 molds being cut and are due just anytime now if they are on time.  I plan to shoot some JSB/BBT comparisons as well as other comparisons.  I need to get my Labradar back from the factory, my screen won't display so I had to have them fix it for me.

[HectorMedina]

Hector, you are never a bother.... I always welcome your opinions and wealth of experience.... Just looking at the area of the base of the projectile, we would expect the LabRadar to lose contact with a .177 cal at half the range of a .25 cal.... while a .308 might do 50% more.... and a .357 double.... or about 4 times that of a .177.... Now that we have seen what the outputs of the datastream from the LabRadar look like.... and realize that their claimed 0.1% accuracy will cause velocities to overlap on occasion, even at relatively close ranges.... I think the "Doppler" effect is not accurate enough to give datapoints every 1/2 yard that are really usable.... so it makes sense to just use the Distance data.... and it is quite amazing how far away the unit can actually track a pellet or bullet....

Bob

Thanks for your kind words and patience.

I will keep an eye out for the results, though I stopped using table/documented BC's about 3 years ago. Just too much work trying to make the reality of ONE gun-pellet-scope-shooter combination into a general figure.

Keep well and shoot straight!






Héctor