JSB New Heavy .25 cal Kings 100 yards half inch group and normal Kings group.

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Yrrah

Yrrah

Member
Apr 1, 2015
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NSW, Australia
While at the farm last week I had some time to play with the Labradar to get some data for BC and ultimately Cd data.
Coincidentally I did some other experiments.
In a rare excellent conditions window I shot just two group with the new Heavy 34 gr Kings and one with the old 25.4 gr Kings .
Below are the results ( the sight in group with the HKs is not shown ).







This is probably the first MOA/ half moa group shot with the new Heavy Kings. I shall be stocking up with them for sure. They have a significantly higher BC than the originals. I make it 0 yd to 75 yards, at my farm altitude, temp etc on the day, as 0.0537 from 780 fps start compared to 0.0354 at 900 fps start for the lighter Kings.
The initial velocity difference has some effect there but very little.

Some may like to open these for some of the data collected. The first has two pages presently ending with a response to Vance Purdy.
http://www.network54.com/Forum/79537/message/1433136252/Heavy+JSB+Kings+-+BC+derived+and+compared+to+the+lighter+originals.
The second shows how the BC apparently changed according to down range average velocity or to range or to both:
http://www.network54.com/Forum/79537/message/1433167229/A+couple+of+interesting+graphs+-+I+think.
If you think there is too much stuff to read there, have a thought for the fun I've had gathering it and perhaps 50 times more :) :) :) ...
The Labradar is now by far my best toy and worth every cent (US $ 559 + exorbitant USPS freight to OZ) ............. Best regards, Harry.
 
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"Ted"Harry you are going to be solely responsible for the "land grab" on these pellets............;I thought I read that this pellet did well from your fx royals 500. Please confirm this for me!! :)

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Mine is the FX Elite Royale Ted. It is a fantastic rifle when wearing any of it's barrels: The BSA Bowkett .25 barrel (above); the original ST .25; the ST .22 barrel which is deadly with 25.4 gr Monster JSB to 75 yards; the Benchmark .22 3 groove from Dan Brown; and the arrow barrel which shot a .80 something inch five shot 50 yards group using the same arrow for each shot after I destroyed three shooting them at the same POA. It is the through-the-bolt air flow design that makes barrel swapping with indexing so convenient. Also that the pellet does not have to pass over a transfer port in the barrel may help a little, though my BSA Hornet .25 is just as good. I love these rifles.

As for the new Heavy Kings, I already have a significant order in here with our importer distributor which will make a hole in his meagre consignment!
The ones I used at the farm came from Pavel as I had pestered him for over 4 years to make this heavier pellet. It was on the back burner because, I think, the .308 and .375s took off and JSB cornered that scene.

Yes the new bovine runt may be a good match up with this pellet. From my rifle's current tune of 780 fps 46 fpe KE it still has 33 fpe at 75 yards compared to the normal King from 900 fps 45.7 ME to 26- fpe at 75 yd. The difference gets greater with range as the BC is better for the new pellet.
Best regards, Harry.
 
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"Bluestone"Harry, good stuff !

Have you found any difference in BC when using the same rifle but with your FX barrel and using the same pellets ?

Click to expand...
I had a feeling that question would arise.
So I must qualify this by writing that the following comparison came from 5 shots for the BSA barrel and 12 shots from the ST barrel with Heavy Kings and over just 0 - 40 yards. Furthermore that the emerging pellets from the BSA barrel I suspect to have smaller frontal area than those from the ST. The BSA barrel has a fractional full length taper as well as the slight choke as it is hammer forged. So sectional density may be fractionally different. My altitude is a little over 1100 metres and the temp was 13C.

The results were BSA BC 0.0534; ST 0.0426.
For obvious reasons I would not want those figures taken to be some standard to be widely applied; and shall at some future time do a better controlled effort.
Having written that, I recall that some years ago I tested this rifle with ST barrel against my BSA Hornet with its BSA barrel and carefully matched the muzzle velocities within 2 ft/sec at 900 fps. They were then chronographed at 55 yards: Pellets were the 25.4 gr Kings.
Quote from April 2012
"3b. A velocity decay test and computed ballistic coefficient were undertaken with 5 of JSB King pellets being shot over a chronograph at each distance of 18 inches and then at 55 yards at average velocity of 900 fps +/- 3 fps ST barrel and 898.2 fps +/- 2.5 fps for the BSA at 18 inches. The average velocities at 55 yards were 746 fps ST Elite barrel, 31.4 fpe . BC 0.0361 ( 0.0313 corrected to sea level ); and 760 fps, 32.6 fpe, BC 0.0407 ( 0.0352 corrected for sea level ) for the BSA Hornet. (Steve Woodwards BC calculator used). ............... "
There was an obvious difference there too.
Edited for incomplete quote.
Kind regards, Harry.

 
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Harry great work - here and with your many other posts - thank you.

Have you tried analyzing comparisons from a statistical standpoint? ie, the difference in the two groups measured may have occurred by chance alone, random wind zephyr, etc. Usually you need a number of measurements of each variable (in this case pellet A and B), to look for statistically significant difference in mean accuracy. (Group size, deviation from X, etc).

Less shots/group would be helpful too, since some information is lost when pellets fly through prior holes. 2-3 should work, say 12-20 tries per pellet, to compare means.

If you get such data I could help with stats comparison if needed!

Kim

 
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Thanks Kim. I'll keep that in mind.
In this instance I basically wanted to get a feel as to whether the new pellet had real potential. Having shot many many groups over the years I now often just shoot one or two thinking it is most unlikely that they will fall 3 +SD right of mean and most probably be in the +/- 1 SD either side the mean.

However, knowing how hard it is to get 1/2 MOA at 100 yd with even the very best rifle and pellets of any calibre, I know this one group was exceptional - but I will be most surprised now if they don't prove to be as good as the best from this rifle/ barrel. That means 1 +/- 0.5 MOA at 100 yards in best conditions over many groups.
I am looking forward to perhaps getting lucky with them one day with a 1 MOA at 200 yards. Have had a best with the normal Kings of 2.3 inches and seven groups averaging out at under 2.9 inches so we'll see. 

Mostly they will be used for controlling the Aussie rabbit population and the odd fox :) . Thank you too for your interest Kim ... Best regards, Harry.
 
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Thanks Harry. A good statistical accuracy test for mean accuracy would be two-sample T-test, with 12 or more group measurements per pellet. Ideally shot with a vice-clamped rifle (to reduce shooter-contributed error) indoors to remove wind variable.

One could use the same data to look for difference in variance. ie, pellets could produce the same mean accuracy error but one might produce more scatter than the other.

Assuming the heavier pellet is significantly more accurate, why? Higher BC means less velocity loss due to air resistance. So presumably high BC pellet trajectory would be less affected by lateral wind.

Alternately, the heavier pellet may be a better match for your barrel(s), and BC/wind isn't the issue.

Kim
 
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All great Data Harry and very helpfull for my new .25cal heavy king shooting project. This info has me very excited to test these new pellets at speed.
Thank you for taking the time.

Just another little bit of interesting info of retained B.C in different barrel makes, I have noted the same loss of ballistic coefficient between the FX smooth twist and the BSA barrel as you did when I tested them at 50y but interestingly the Lothar Walther sits somewhere in the middle of the other two brands. 

IMO BSA did a very bad thing changing these winning formula barrels as the original lonestars are still proving to be the top of the game in 100 meter BR comps.

The B.C. of a subsonic pellet is an ever changing figure and not an easy one to work out but even more confusing to understand how the different rifling effects it in such the opposite way you might think it would. I am willing to bet it has more to do with twist rate v/s velocity than the barrel's grooves and lands (or lack of) affecting the pellets aerodynamics due to head and skirt groove deformations.

Here are two JSB Kings 25.4gr pellets pushed through a L/W barrel on the right side of the pic and the above mentioned BSA barrel on the left.. the BSA has a VERY tight choke.

 




I cant seem to find my smooth twist pellet photos but the above is a .22 example,( will edit this when I locate the images on my cluttered hdd )
The S/T pellet shows the least amount of deformation from its trip down the tube but still seems to shed more speed in a lesser distance... 
All interesting stuff.

​The S/T v/s L/W debate always makes me smile to myself, they are both great barrels and inside 50y where 99% of air gunners operate you would be hard pressed to single the "better performing" design. 
I say this as I clench even tighter to my collection of old stock BSA barrels.. :D
 
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This is long but it encapsulates much of what I found back then of the ST barrel's treatment of pellets, spin rates and stability.
Previous to getting my own ST FX rifle, I had asked Dan Brown to do a particular test shooting marked pellets through screens to establish if the pellets' spin rates conformed to the "rifling" in the last inches of barrel. Fredrik told be the "rifling was 1:16". The results of my tests with my rifle are shown in this report. After discussion with Fredrik he did his own test and confirmed that what I had been saying was fact, though the actual rates varied from mine and from Dan's . But there had been many iterations of the barrels in the meantime, Mine being the 16th, Fredrik was on the 18th and Dan's was somewhat earlier than mine. There have been others since.
Any who take the time to read this report will realize that things are never simple and that some of us have spent effort and time to move our understanding forward.

http://www.network54.com/Forum/79537/thread/1333679371

If nothing else, readers please note the stripped flats on the shot pellets and which do not conform to the pic of definite lands and grooves in the barrel pic. Also note the pellet with dirt on its head and the one stuck in the tree bark showing that the group shot at 183 yards was fair testament to the long range stability of the shots.
Roughly 10,000 rpm + drag can obviously do what 30,000+ rpm can do. The two comparative 100 yd groups give further proof.
However so far all my tests have indicated my old BSA barrels, for whatever reason, produce higher down-range velocities than my same calibre ST barrels in .25 and .22 when launched at the same mv.
John Bowkett has indicated in the past that the .25 BSA barrels were nearer .243 effective than .2500. I think mine are at least as small as .247. Kiwi Wingman's pic of the pellets seems to support the concept

If re-posting any of my research is a worry here just let me know,

Best regards, Harry.
 
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Harry,

Hope you are still out there, and subscribed to this thread.

I have been testing the .25 Heavy pellets extensively for the past 4 weeks. I do not have that fancy gizmo of yours that you use to calculate BC, but I have set out targets every 10 yards from 50-100. I have been shooting exclusively with Smooth Twist barrels. Pellet drop data suggests a BC of .042-.044. How closely does this match your own data? Does the .25 Heavy have a better BC than the 44gr .30 JSB?

ted
 
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"Ted"Harry,

Hope you are still out there, and subscribed to this thread.

I have been testing the .25 Heavy pellets extensively for the past 4 weeks. I do not have that fancy gizmo of yours that you use to calculate BC, but I have set out targets every 10 yards from 50-100. I have been shooting exclusively with Smooth Twist barrels. Pellet drop data suggests a BC of .042-.044. How closely does this match your own data? Does the .25 Heavy have a better BC than the 44gr .30 JSB?

ted
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, Ted, buried in the thread above are the figures of 0.0534 for the BSA barrel and 0.0426 for the ST barrel at my altitude. I do not think I have done another ST test since then but may try another for you as opportunity allows.
My ST barrel shoots the heavies very well.
I very much doubt that the .30 pellets would have a better BC than the .25 heavies shot from my BSA but I may be wrong.
Best regards, Harry.





 
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"X-Hairs"Harry/Ted - Can either of you provide a link to these NEW JSB .25 Heavy pellets? I'm confused whether we are talking about the MK1 or MK2 versions. FYI - I plan to use these in my FX Bobcat.25 MK2. 

With gratitude!
Click to expand...
I am shooting the Mk1 original 33.9 gr heavy. My FX Elite .25 is single shot so no magazine. 
Kind regards, Harry.
 
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I got a BC of .0434 at 110ft ASL and 17 deg celcius for the Mk 1 heavies in a S/T. Al testing I have done says yes they have a higher BC than the 44gr .30cal bricks although I have yet to test the .30's in a smooth twist, I would estimate the results will mirror the .22 and .25cal results of the S/T having a lower B.C than in the L/W Ive been shooting.
How have you found the accuracy of the .25 heavies in the S/T at 100yds Ted? 
 
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"Wingman"I got a BC of .0434 at 110ft ASL and 17 deg celcius for the Mk 1 heavies in a S/T. Al testing I have done says yes they have a higher BC than the 44gr .30cal bricks although I have yet to test the .30's in a smooth twist, I would estimate the results will mirror the .22 and .25cal results of the S/T having a lower B.C than in the L/W Ive been shooting.
How have you found the accuracy of the .25 heavies in the S/T at 100yds Ted?
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More info confirming my numbers! :) Thanks Phil.

Accuracy is definitely there. This is a full magazine (16 shots) at 100 yards shooting through a smooth twist barrel (FX Impact). These shots were filmed through the scope with a slow-motion camera, and will be part of the final review for the Impact. The two low shots were #3 and #4. The day was slightly breezy, and I suspect a small down draft got hold of them as the wind came over the bunker. Shots 5-16 were MOA. Slow motion footage revealed clean flight (no wobble), and there was no "slice" or "draw" - strait up; strait down.

The crazy thing is that FX did not design the barrels to shoot the new Heavy .25 pellet. They didn't even know how well their ST barrels shot it until I showed them my data. The .25 barrels are essentially designed to shoot the .25 king pellet. So, there may still be room for improvement!

 
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