.20 Caliber JSB 13.72 Stability -> Theory

[SpiralGroove]

Hey Guys,
This may sound kinda crazy ... but I've never sounded like that before - Right?

Now that I've been shooting a .20 caliber pellet in my HW80 and HW95 platforms - I have the following Theory.  The JSB 13.72 grain pellet seems to be more accurate (better stability) at velocities > 710 fps .  This sounds foolish on the surface, but after shooting multiple guns, the pellets seems have (significantly) better command above 15 fpe.  My spring guns are shooting between 720-800 fps.   
Maybe the difference is also related to how fast the gun exits the barrel or harmonics (advantage seen on both short and long barrels) - IDK.

Is this a coincidence or what?

[Motorhead]

The CHOIR already knows this  ... Lol  No preaching required 

No mystery I'm a huge .20 cal fan and been using the caliber and JSB 13.7's for field target competition now going on what i think will be season #5 in 2020.
Shot in PCP's at @ 800 fps being just > 20fpe has proven itself to be vastly superior to even .177 in the same weight class at equal speeds.

In the HW barrels I use my BC value at that speed is an astounding .040 to .044 pending elevation from sea level to @ 5500'.

Yup the Lowly .20 may not be an everyday caliber for most, but for those in the know, it's going nowhere !

[Mark 611]

U hit it MH!! Kirk, listen! ur finding out what a lot of us already know about the .20cal, whether its the 11.42 or the 13.73gn pellet, their both excellent in the right power plant? even in a smaller power plant the 13gn pellet will give excellent accuracy, but the drop is more significant, at longer ranges,

[SpiralGroove]

Hey Guys,
This may sound kinda crazy ... but I've never sounded like that before - Right?

Now that I've been shooting a .20 caliber pellet in my HW80 and HW95 platforms - I have the following Theory.  The JSB 13.72 grain pellet seems to be more accurate (better stability) at velocities > 710 fps .  This sounds foolish on the surface, but after shooting multiple guns, the pellets seems have (significantly) better command above 15 fpe.  My spring guns are shooting between 720-800 fps.   
Maybe the difference is also related to how fast the Pellet exits the barrel or harmonics (advantage seen on both short and long barrels) - IDK.

Is this a coincidence or what?

Mark,
My comments are about the .20 JSB 13.72 only, I haven't found any other .20 pellet that compares.
However, when my HW95's were shooting in the 675-690 range, even the JSB 13.72's were sporadic -> hit or miss.  When I re-tuned (using more powerful springs) to shoot over 700+ fps the pellets command increased very noticeably.

I'm not try to waive the .20 caliber flag as much as relaying how velocity seems to help the JSB 13.72 pellet in particular.  At 675-690 fps, the JSB is still better than it's other .20 counterparts, but at greater velocities it seems to be better than anything I've tried regardless of caliber in any air gun.... That's the Theory .

[jason miller]

My external ballistic knowledge of pellets is pretty feable, but what are the chances that the twist rate in your barrel is not quite fast enough to stabilize that pellet, and the bump in velocity pushes the RPMs up just enough to get it to settle down?

[SpiralGroove]

My external ballistic knowledge of pellets is pretty feable, but what are the chances that the twist rate in your barrel is not quite fast enough to stabilize that pellet, and the bump in velocity pushes the RPMs up just enough to get it to settle down?

Could be, but I don't think so... however, I don't know for sure - gut feel time
I bet all Weihrauch airguns are rifled with the same twist rate; the HW30S shoots great at 575-700 fps.

[Mark 611]

Several things come to mind here for me on this, pellets from different manufactures use different lead compositions, this leeds to drag in the bore with softer lead, which effects velocity, lets say ur rifling is not perfectly smooth? and the pellet is being marred as it go's down the tube, once it leaves the barrel it becomes unstable, or ur crown is not perfect? this will definitely cause accuracy issues, Heavier pellets are generally more stable, they have a longer bearing surface to stabilize the projectile as it go's down the barrel, It will fly truer longer, pellet fit, barrel twist, all come into play, velocity is what it is, just throwing this out there, my HW35 .22cal loves the 16gn AA Fields, shoots them @605fps, where as the H&N FTT's 14.66gn run @640fps, both are very accurate from my barrel, but I have no problems shooting the 16gn pellets out to 60yds and thumping birds out of the trees around my house, the 16gn pellets are my preferred pellet for this rifle and I trust this pellet at these distances for accurate shots vs the lighter faster FTT's, I hope this makes since?

[jusanothajoe]

Hey Guys,
This may sound kinda crazy ... but I've never sounded like that before - Right?

Now that I've been shooting a .20 caliber pellet in my HW80 and HW95 platforms - I have the following Theory.  The JSB 13.72 grain pellet seems to be more accurate (better stability) at velocities > 710 fps .  This sounds foolish on the surface, but after shooting multiple guns, the pellets seems have (significantly) better command above 15 fpe.  My spring guns are shooting between 720-800 fps.   
Maybe the difference is also related to how fast the Pellet exits the barrel or harmonics (advantage seen on both short and long barrels) - IDK.

Is this a coincidence or what?

Mark,
My comments are about the .20 JSB 13.72 only, I haven't found any other .20 pellet that compares.
However, when my HW95's were shooting in the 675-690 range, even the JSB 13.72's were sporadic -> hit or miss.  When I re-tuned (using more powerful springs) to shoot over 700+ fps the pellets command increased very noticeably.

I'm not try to waive the .20 caliber flag as much as relaying how velocity seems to help the JSB 13.72 pellet in particular. At 675-690 fps, the JSB is still better than it's other .20 counterparts, but at greater velocities it seems to be better than anything I've tried regardless of caliber in any air gun.... That's the Theory .

Both .20's I owned liked the FTT's better than the JSB's

[HectorMedina]

@ Kirk.- There is a lot to your "theory".

@ Scott.- The JSB 0.20's were designed for twists around 400-440 mm's, which covers the span between L-W and HW barrels. MOST after market HW barrels are NOT choked, very few are. As long as your barrel's last 3" are uniform, it should be accurate. As long as the initial pressure spike is not too harsh, the JSB 0.20" will retain its shape well, BUT BC's as high as slugs would have seem to indicate that the shape has shifted from one to the other. The question here is if you have recovered pellets using a loose Dacron filled cardboard tube. It's easy enough that if you can, the pictures would illustrate us all.

@ Jason.- What stabilizes a waisted pellet is MOSTLY aerodynamic "funneling" (NOT drag), as it is a flange-stabilized projectile and if fired from a good, consistent, and uniform barrel, even smoothbored; pellets will stabilize well under 500 fps.
Gyroscopic forces in MOST cases play AGAINST stability when using waisted pellets.

@ Mark.- Antimonium, in general, is a worse "bearing" metal than pure lead. ALL pellet manufacturers use either pure lead (down to three, or four, digits depending on the quality of the line), or at most 2% Sb (Antimonium). MOST common alloys run between 0.4% to 1%, the old Crosman Premiers being the outlier in the 2% region.
Smoothest ride is for lead on lead, but it is not sustainable at above 500 fps because above that speed lead tends to smear on steel (specially highly polished surfaces), and then there is an accumulation of "smears" one on top of the others, specially at places like the choke start.
Antimonium hardens the alloy and so, prevents deformation (up to a point). It also makes pellets more "shippable". In many ways it is a necessary evil for us airgunners. I tend to think of it as caffeine: a little goes a long way and it is useful, too much is a problem.
In general, I would agree with you that the AA/JSB  Jumbo Exact 16 grn 0.22" is far superior to the H&N FTT 14.66, though the FTT's tend to be "fuller" in the head and so SOME barrels will prefer them for the same size of nominal head diameter.

@ Derek.- As you can read above, it all depends on the bore size of your barrels.


Now, If we make a bit of history, it was back in 2000-2001 that the idea for a 0.20" cal JSB first started.
We discussed a LOT the weight we would target (pun intended) because Crosman was doing stupid things with their Premiers.
It was also the time when the FT world was irremediably split and the 12 ft-lbs level was declared the one and only legal level.
Why was this important? Because no other airgunners at the time would pay $20 ($31 of today's money) for a box of pellets. And without the support of high volume FT shooters, the 0.20" cal Premier had no standing in the Exec room at Crosman to be sustainable. SO, it went the way of the Dodo bird.

In those days, most people shooting 0.20" cal. were using PCP's, yes a bunch of RX-2's had been built, but they were too much of a bear to use for long matches. So high volume shooters shooting 0.20" cal. was basically the realm of the PCP guys.
Back then you could choose between the Baracuda (13.6 grs), or the Premier (14.3 grs), the FTT was some way back in performance, specially at long range.
JSB had just come out with the Jumbo Express (14.3 grs), and so it was heavily argued that using the same pre-form would have economic advantages.
BUT, the main market was Europe, and within the more common limited power market, the "barrier" between "13" and "14" grs. pellets was deemed to big to overcome. It was also not a desire to compete head to head with Crosman in what was one of the widely prized and praised models.
So, the challenge was to design something SLIGHTLY lighter, that would be more efficient in absorbing the energy from the common powerplants, and still have the BC of the Crosman Premier.
To this effect we went through three iterations of different skirt/waist/punch/head designs to end up in what we now know.
And, yes, it was designed from the ground up to be suitable at 650 fps and up which is about 13 ft-lbs and up. Of course, it all depends on the barrel.

After MANY years, the "heavy" (15.7 grs) version is here and, at least in quality barrels (L-W), they seem to be just as accurate as the original "mid' ones.
I've been testing a DIANA 54 with them and after some fiddling, they shoot real  good.
Of course, the 54 can throw the "mids" at about 23 ft-lbs and the "heavies" are limited to 20 ft-lbs. But that is still a lot of power to put into a tiny area.

While we do not think there is enough market to warrant an "Express" (light) version, there is room for a non-lead 10.5 grs, 0.20" cal. OR a 9 grs. one.

If you could vote, which one would you vote for?

We'll see . . .

IWA has been "postponed" to some indeterminate date in the future due to the COVID-19 thing, but I still have to go to Germany.

Keep well and shoot straight!





HM

[WHITEFANG]

The CHOIR already knows this  ... Lol  No preaching required 
BUMP!!
I am a fan of the H&N PELLETS. JSB just seems to have changed? But I am shooting the JSB 15's out of my PCP. BUT I am pushing them harder than 800 fps. 14.3 Old Crosman,  Also shoot well out of the R1 .20 and the Baracude is its favorite pellet. 50+ yards are kills. For me 800 has always been my starting sweet spot with the 11"s anything over that had been a plus. Then you go heavier.
Bump on Mark
The .20 has been a long time debate with many opinions pro and con. No need to defind the caliber. You either like it or care not for it. As MH, IT'S GOING NOWHERE

Hector has gone in depth as well with good info. The 14.3 shot in most of my .20  spring and in the Raw .20, THAT was its favorite pellet shooting 940 fps with no accuracy issues out to 100 yards. No barrel fouling but an LW BARREL. I need say no more on the .20 caliber. It's all out there on many forums and is one of the most debated calibers.

[north country gal]

Okay, I'm not adding much in the way of technical info, here, but I shoot the JSB 20's in my Sheridan pumps and the accuracy I get is simply extraordinary, as in consistent sub one inch groups at 50 yards with six pumps, which would keep me under that 700 fps. No other 20 cal pellet I've tried matches it. Given that we have a nice assortment of Sheridans, we keep a good stock of the JSBs on hand.

[Motorhead]

Hector,
In BOTH cases of my primary .20 cal FT guns ... there VERY ABRUPT and Violent in air delivery being VERY high amplitude Short dwell firing cycles.
One being a Daystate MK-3 with an added HuMa reg and larger porting. Other a RAW TM-1000 using a custom valve, very light hammer etc ... SNAP !!! is the extent of either firing being motionless except that of the pellets mass being accelerated.

Don't feel either is distorting the skirts shape simply because there ES is so tight and accuracy so consistent shot after shot.  But then again

[fwbsport]

So after finding out in my case with the HW80 .20 the heavy JSBs shot more accurately than the light JSBs.  We're talking 3 grains? That much difference?

The situation is complicated by the addition of the HW98 which shows no difference in accuracy off hand at 25 yards (the usual for me).

The HW97K-T likes the LIGHT JSBs.

So now I have to have BOTH weights to attend to whichever rifle!

 

[WHITEFANG]

Hector,
In BOTH cases of my primary .20 cal FT guns ... there VERY ABRUPT and Violent in air delivery being VERY high amplitude Short dwell firing cycles.
One being a Daystate MK-3 with an added HuMa reg and larger porting. Other a RAW TM-1000 using a custom valve, very light hammer etc ... SNAP !!! is the extent of either firing being motionless except that of the pellets mass being accelerated.

Don't feel either is distorting the skirts shape simply because there ES is so tight and accuracy so consistent shot after shot.  But then again

Totally agree MH. If we are pushing the pellets hard and the guns thread a needle? Shooting long ranges with still hitting intended aim point,  I would have to agree. .
Thee Daystate and Raw are LW barrels.
All the AF guns are LW. All my . 20 Diana rebarrels in . 20 were the LW. We know the LW Barrel has a really tight choke. More so than many.

LOW power spring guns having to really push the. 20 might? But never seen that in my days. But anything is possible these days.

[Lastdog]

Having bought 5 tins of Eun Jin .20 pellets for an ace 500 max that was miss marked and turned out to be 22. This combined with Air Force having .20 barrels at 1/2 price and deer season being over decided to switch my .30 to a.20. Got the barrel today and tried to insert a pellet . Jsb’s fit perfectly. The Eun Jin’s head slides in but stops when they are only half way in. The Eun Jin’s are about twice as long as the Jsbs. So my question is does a condor have a maximum length that it will accept. Hope someone knows. The barrel is not in the gun yet but it looks like it will not seat all the way in.
The idea behind this entire experiment is to have a high speed, flat shooting varmint gun.
Hope someone knows before I try to put. 10.5mm long pellet where it should not go.
Always liked .20s out of my silver streak.

[WHITEFANG]

AF barrels are landed out all the way to the leade pellets seat and to my knowledge the skirt is bigger on some. Hunter supply seated in the . 25 barrel till it hit the rear ring. Forced it in and several shot but no accuaracy. Nelson fit.  Heavy pellets get longer with weight increase.
Some leave the remaining hanging out and shoot. My experience is the gun can dump the tank doing this with the rear binding. That extra dimension crowds the bore causing a ressitance  on the valve. Dumped a 3000 psi fill over the chrony after the 3rd shot. Free loose handed pushed me into the wall.
About popped my pants. NOT SURE this helps.
Seneaca pellets shoot fine and fit in . 25 Cal. Just nasty not good QC. Same pellet as Eunjin. 43 gr are doable but the . 35 he do not shoot good at all out of my gun.
No experience in the . 22 with them.  Probably no help⁉️

[SpiralGroove]

Hey Hector - Great historical information .
The only reason I've been experimenting with different velocities of the JSB's, was I wanted to replicate the amazing accuracy seen using the .20 caliber JSB (13.72) in my HW80 .  So... I decided to try shooting .20 caliber ammo with my lighter platform R9/R10 guns. 

Unfortunately, my initial results (@675fps/690fps) they were not nearly as consistent vs. the HW80 shooting at 800 fps?  For a couple of years, I'd been wondering if the results of the more powerful gun could be replicated.  Even though the gun had substantial recoil, it was incredibly accurate (minimal hold sensitivity) out to 80 yards.

After increasing the spring power in both the R9 and R10 (now shooting between 720/740 fps or 15+ FPE), I notice they became much more consistent - approaching my HW80. 

Because I use the "Motorhead school" of cleaning my barrels, I knew they were at their best.  Hence, either an increase in pellet velocity, decrease in Dwell Time or positive influence of barrel harmonics must have made the difference.

That's why I posted -> JSB pellets seem to like more velocity than 690 fps.  The icing on the cake, is the great accuracy remains stable over a wide range of 13 yards to 80 yards with differing barrel lengths.

I still very much Love the .177 caliber pellet, but the .20 is a great alternative with more Thump . 

[Lastdog]

Kirk, I know we are talking two different platforms but I am trying to get to a similar goal. That is using the .20 at a high FPS to get a flat and accurate trajectory over a longer distance to minimize holder over and still have a good punch down range. Any ideas from your experience what would be a good weight .20 pellet and at what speed would be a good starting point. I need all the input I can get. The only limited experience I have with .20 is with a multi pump.

Fang, thanks for the info. Don’t want to poop my pants.

[SpiralGroove]

Kirk, I know we are talking two different platforms but I am trying to get to a similar goal. That is using the .20 at a high FPS to get a flat and accurate trajectory over a longer distance to minimize holder over and still have a good punch down range. Any ideas from your experience what would be a good weight .20 pellet and at what speed would be a good starting point. I need all the input I can get. The only limited experience I have with .20 is with a multi pump.

Fang, thanks for the info. Don’t want to poop my pants.

James, IDK exactly
However, if Motörhead likes the JSB at 800 fps, try that combination: either in the 13.72 or 15.89.  Hector has said they're = in accuracy .

[dtdtdtdt]

First:  I have not shot the .20 too much. 

Hector built me one of his special Diana 54!  He recommended the JSB Exact 13.73 pellets and tuned it for them.  It shoots amazingly well.  Energy is about 20fte.  Velocity is between 850 and 900 f/s. 

Just got it out after a winter's sleep yesterday.  First shot was pinwheel in the 10 ring.  It required one click left adjustment to get it exactly centered.  50 shots later - none were over 1/8" from the center of the 10 ring at 17m -indoors. 

Today, its little brother gets the same treatment and we see how it goes. 

A few years ago, I did a test of over 80 different pellets ranging from very light to very heavy, lead vs non lead, and composite plastics in my .177 D54 that is more-or-less stock.  Recorded velocity, group size, pellet weights, etc. All the metal pellets were waisted pellets.  Plotting group size versus velocity showed that 800-900 f/s was optimal for accuracy.  A couple outliers - one of which was a non-lead pellet but pretty consistent with others.  Composite pellets were generally poor and gave off chemical smells and showed burning in the bore - patch came out black!!  Kodiak Match 10.6gr pellets have dealt with over 400 chipmunks in the past 6-8 years so I do have unsatisfied victims. 

I have no access to the kind of computing power and programs that I used to for data reduction but feel safe in saying that the best range for velocity to give overall best accuracy is around 850f/s. 

Chipmunk season is upon me so I'll have more live target data soon.  I plan to use the 20 for most of that.

Cheers!!