$100 worth of JSB Knockout Slug Velocity Data

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mmahoney

mmahoney

Member
Feb 20, 2017
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Wyoming, United States
 



The goal of this experiment is to determine if the JSB slugs have a preferred velocity. I will be collecting enough data to be certain within a 10% margin of error (at least 432 groups). So far, I’ve heard claims that slugs like to “go fast”, but reliable data on the topic is nowhere to be found. I believe that it is possible that one of the first respected testers of slugs shot a few good groups at a high velocity and mentioned the results of his small sample size online. These results may get repeated over and over again by others online giving them the illusion of being conclusive (anchoring bias).

Testing procedure: 


  • A minimum of 432 three shot groups (to reach the margin of error I’m willing to accept) will be fired out of my Taipan Veteran at velocities ranging between the low 800’s to low 1000’s (from 36 to 60 FPE). I’ve selected 3 shot groups to reduce the effect of subtle changes in the wind. 

  • The average velocity of each 3 shot group will be measured using both a FX and a Caldwell chronograph. The data will be reported using the Caldwell velocities because it has proven to be a touch more consistent than the FX.

  • Each group will be shot at a different velocity by adjusting the hammer spring on my Taipan Veteran in ⅙ turn increments. 

  • Group sizes will be measured center to center and reported in mm. 

  • Data will only be collected in calm wind conditions to minimize error introduced by the changing wind conditions.

  • All groups will be shot using a single shot tray.

  • All groups will be shot at a distance of 50 yards using a Caldwell Stingray gun rest.

  • All groups will be recorded and no outliers discarded.

  • All groups will be fired out of the same gun: a .22 cal Taipan Veteran Long. The Huma regulator has been raised to 150 BAR and a stronger hammer spring has been installed to allow the gun to shoot up to 60 FPE. The trigger of the gun is set to 3 oz. which greatly reduces the chances of pulling a shot. The gun has been cleaned and 10 shots fired through it to season the barrel before testing began.

  • I will be letting the gun shoot the groups and remove myself as much as possible from the system. This includes keeping as much of my body from touching the gun as possible to keep variables such as my heartbeat from factoring into the data.

First 35 Shots of Data:

Linear

wzxMfxvyImOf-u1OXvjDyCdBwODX1KAJ9ArDw7fOiGHqAisksaIb597BW_wy9zOvoMptpKIfKyTn-i7xxx1wqTsFp4lSghb_ThxqypQGNSEjR7saneGWw20pp7p_dyPa9CAheV0-


The first 35 groups show no relationship between the velocity and group size. Notice how flat the trendline is and how low the R squared value is.



8th Degree Polynomial Trendline:

XR76UW0Wu8fIaG0ijv5NTGFY6EiqCkrhq34K1LDpKn5WBtX7xWXdFGSV_c_R9crlaj_6ifloYQHCFSr2PTKLF5xFV0IFEHGDwJeVfzM-F21W84VHBpWTUm-dW5J_aYCG2jkp0DRM


In this graph, the computer has matched an 8th degree polynomial to the data. The R squared value is still very low which tells us that the velocity and group size do not yet show a very strong correlation. The 3 dips in the curve at about 860 fps, 950 fps and 1020 fps seem to indicate that these velocities might show promise in producing smaller groups than other velocities, but this may just be noise in the data. Right now there is not nearly enough data collected to make any conclusions. I will update this graph as the data comes in…
 
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Good stuff! I like data.

Lots of conjecture in this little hobby and your experiments (and documentation) are always a breath of fresh air. 

Thank you. I'll be following. 

(Would be very interesting to see this same experiment with the JSB Monster RDs in .22 that seem to be at the front of the pack for 100yard paper shooting right now. Ie, do they get more accurate/better BC/group more consistently as speed increases, and does that perceived improvement in accuracy have a linear relationship with speed, are there any plateaus, or is the benefit of going from say, 920 up to 960 more pronounced than going from 880 to 920?). 
 
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Awesome, but of course your data will only represent if the JSB KO like being shot at a specific velocity FROM A TAIPAN VETERAN, more precisely your TPV barrel, which may be different to other TPV barrels and is certainly very different in bore dimensions and twist rates etc. to other manufacturers specifications.

The data would be extremely meaningful if you used 5 or more guns from different manufacturers of course, are you able to do that?

I have never seen a TPV, in fact they aren't even sold in this Country as far as I am aware, one thing I am aware of is that my testing of slugs for JSB (and others) leads me to believe that they are the least fussy of any slug on the market. They tend to shoot well in all barrels and at a fairly wide range of velocities.

I have the ability to test them in about a dozen different guns and have done and the results can be quite different, even with different liners from FX, which Ted demonstrated recently.

Do really like your methodology of testing though, mine relies more on memory LOL!






 
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...or is the benefit of going from say, 920 up to 960 more pronounced than going from 880 to 920?). ...
Click to expand...

If the distance were 100yds rather than 5Oyds, then the improvement from higher muzzle velocities would likely be more pronounced.
Click to expand...

Agree, would just like to see some data (even if it's only from one gun) supporting this. 

I'm sure you've read it and likely understand it more fully than myself but RSterne makes some pretty compelling arguments for 860-880fps being the optimum speed for diabolo pellets. I'm paraphrasing, but he states that a diabolo pellet experiences less wind drift at those speeds. The .22 JSB MRD is a little bit of a wild card though, in that it is somewhat a slug but still a pellet (not a very pronounced waist). Made even more interesting by shooters seeing improved results in the wind at high speeds, anecdotally. 

I'd simply like to see some well documented data to support or disprove this, even if it's only from one gun. 
 
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Woke up to dead calm conditions so shot 35 more groups. My gun had trouble getting over 1000 fps per second this morning as pressure of the tank I was tethered to dropped below reg pressure. I may start making finer adjustments to my hammer spring in the lower velocities and larger adjustments at the higher velocities to try to keep the data more spread out. As you can see I am starting to get some clumping of data around 950 fps.

1598110469_6438265325f413b05517628.72979614.png


After 70 groups, the linear correlation is still very weak. No real changes here.

1598110557_16350198995f413b5d4d3384.23868724.png


Our three dips from the previous data can still be seen at about 860, 950, and 1020 fps. As mentioned above, none of my groups averaged over 1000 fps in this test batch, so that section of the curve is unchanged. 
 
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@Scotchmo

I'm shooting at 50 because I can shoot that distance in my backyard without needing to pack up and head to the shooting range. The window for calm conditions is often short so I'm set up at home to take advantage when they arrive. The group sizes are significantly different enough at 50 yards for me to measure significant differences with my calipers.

@Franklink

I've already completed this same experiment using the JSB Monsters but haven't posted the results. I'll post them after this data set is completed.
 
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@Spray1Mark

I only have the one gun until the Delta Wolf becomes available to try to steal the Veteran's championship belt.

Also, I think the real question being answered is what velocity is needed to get the spin of the slug to its "ideal" (If there even is an ideal). If I knew the math, rather than velocity I would graph against the rate of slug spin. Testing 5 different barrels wouldn't necessarily change the data. What is needed is another barrel with a tighter twist rate that can extend the data past what can be accomplished by my Veteran's barrel. I expect the data to be pretty universal for any gun that spins the slug at similar velocities. It is completely possible that my gun is not able to shoot the slugs fast enough to achieve a "best" spin rate. The data I'd be interested in seeing is a slug fired through a barrel with a faster twist.




 
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I think it’s wonderful that you are taking on a project of this nature. It will be interesting. It’s extremely difficult to do this because to be significant you have to eliminate all the extraneous other variables which come into play. Wind shooter error on and on.
I don’t do well with this stuff because I’m not a very patient person.
I was talking with a champion benchrest shooter a couple days ago. He shoots at 850 yards and beyond and has won all manor of competitions. He told me just some of what he has to do to accomplish his results . I just don’t have it in me to even consider something like that. But I admire those that do.
I think you have to be extremely careful how you set up your experiments. This benchrest shooter said he weighs and sorts his primers. My thoughts? Boy that could easily be consider anal and how would you possibly set up a testing method which would be accurate enough to provide an answer.
BUT I agree too much and probably most of what we talk about is nothing more then anecdotal. At the least you are trying.
 
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@Scotchmo

I'm shooting at 50 because I can shoot that distance in my backyard without needing to pack up and head to the shooting range....
Click to expand...

I understand. I shoot pellets in my backyard (30yd range). I shoot slugs when at my friends ranch or at the local gun range. For 10-60yds, pellets are already a great/better choice. Sure, it is nice to know that slugs can shoot accurately at 50yds, and it's an OK first step, but I care most about how they hold together at 75+yds, since that is where they will be used in my case. I would not spend too much time trying to optimize for 50yds though.
 
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I have not much experiance with slugs but according to Bob'o https://www.youtube.com/watch?v=biIg0iiZjFU, a small difference in repressure or speed can make a huge difference. So dialing hammer spring only, you will probably find the speed where a particular gun shoot best, in relation to the regpressure. But by changing regpressure at a certain speed, you are changing the parameters, not only the speed.
 
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@tor47

The reg pressure is staying set throughout the test. I'm only adjusting the velocity and by extension the speed at which the slug spins.

Also, I'm not looking for the ideal velocity of these slugs. I know for certain that the JSB Monster Redesign pellets shoot better in my gun at distances up to 100 yards vs any slug currently made. I want to know how much difference velocity makes to slug accuracy. I know the "common knowledge" is faster is better. I simply want data to support or refute that.

@steve123

I started with a clean barrel. I plan on cleaning it halfway through the testing (after about 600 shots) and then again when I'm done. I adjust the velocity after each group, so no one velocity has an advantage of being shot through a cleaner barrel than any other velocity. 
 
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Was lucky enough to have great shooting conditions both last night and early this morning and collected 105 more groups worth of data. We are almost to the halfway point now.

1598193642_9331669845f427feaec87b5.36555339.png


As you can see, the linear data has been consistent throughout the experiment so far and shows changing velocity/spin speed of the slug doesn't affect group size.

1598193758_17030692465f42805e24fa55.37782501.png


The 8th degree polynomial is also flattening out. It is getting harder to make the argument that there is a velocity tested that is resulting in tighter groups.



Also, I stopped being lazy and looked up the formula for calculating the RPM of a bullet's spin. The equation is pretty simple: RPM = (velocity x 720)/Barrel twist rate.

Therefore this data should be fairly standard for the KO slug out any barrel shooting at a spin rate between 32,500 RPM and 41,700 RPM. This assumes that the twist of my CZ barrel is 1:17.7" 




 
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I've already completed this same experiment using the JSB Monsters but haven't posted the results. I'll post them after this data set is completed.
Click to expand...



Yes, please DO!! 😊

This is soooo good! Real life data, carefully recorded, with proper test protocol, statistically sound, AWESOME!



Thank you for doing this for us! 😊

I so much rather have research than researcdotes or researgut-feelings.



Give this man a green ball! 👍🏼😄

Matthias

1598200146_8852217445f4299520a88e1.23664291.png





 
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Added more data. We are not quite to the half way point but after 209 Groups, this is what the group distribution looks like:

1598397869_4312321565f459dadc6e524.39081560.png


The data couldn't be more flat. It looks like the slugs don't care what speed you shoot them at up to about 1025 fps. Maybe they like being shot even faster than 1025fps (or spun faster than 41,700 RPM) but I wouldn't bet on it. Lets zoom in on the trendline and see if we can drill down the average group size the data says my Veteran is shooting the .216 diameter KO slugs at.

1598398161_1629961855f459ed14df673.56429003.png


As you can see, the trendline shows that average group size is 14mm at all tested velocities. 

The 8th degree polynomial graph is also flattening out and looking much like the linear graph. This is to be expected if the data truly shows that changing velocity doesn't affect group sizes.



1598397856_11477989495f459da00f1db7.51432539.png

 
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