CompareComparing...

JSB Exact King Heavy MkII 33.95 Grain .25 Caliber Pellet Test Review

Overview
Testers

Doug Wall
Stephen Archer

Caliber

0.25

Test Date

February 20, 2020

Source of Supply

Predator International, Inc.

Condition

New

We Like

Excellent head diameters
High Ballistic Coefficient
Match manufacturer's claims

We Don't Like

Rather variable weight (maybe we got unlucky)
Not much else

HAM Rating
Comparison to Makers Claims
100%
Most Common Head Diameter
45%
Variation in Head Diameter
100%
Most Common Weight
35%
Variation in Weight
35%
Most Common Length
45%
Variation in Length
60%
Dirtiness
45%
Hard Air Magazine Test Conclusions

JSB Exact King Heavy MkII 33.95 Grain .25 caliber pellets combine heavy weight with a high Ballistic Coefficient and excellent control of head diameter.

This is a great pellet for the long range shooter. The tin of pellets tested by HAM did show more variation in individual weights than is normally found in JSB products, however.

But in spite of this, these King Heavies earn a HAM Bronze Award. That backs-up their outstanding reputation for long range accuracy. HAM will be including them as a standard test pellet for our high power .22 caliber PCP air rifle reviews.

59%
HAM Rating
You have rated this
Full Review

VALUE FOR MONEY

JSB Exact King Heavy MkII 33.95 Grain .25 caliber pellets have an outstanding reputation for accuracy – particularly at long ranges. They combine this with a heavy weight, approximately one third heavier than the average 25 Grain pellet in the same caliber.

As lead costs money, this significant weight hike over an average .25 caliber pellet means that the King Heavies command a premium compared to lighter pellets. However this is not excessive, as we can see from this price comparison chart.

JSB Exact King Heavy MkII 33.95 Grain .25 Caliber Pellet Test Review

The high weight of JSB Exact King Heavy MkII 33.95 Grain .25 caliber pellets is combined with a high Ballistic Coefficient of 0.046. This means that these King Heavies are attractive to both the long range airgun shooter and hunter for larger game.

JSB Exact King Heavy MkII 33.95 Grain .25 Caliber Pellet Test Review

BUY FROM PYRAMYD AIR
JSB Match Diabolo Exact King MKII Heavy .25 Cal, 33.95 Grains, Domed, 300ct 0.25
BUY FROM AIRGUN DEPOT
JSB Exact King Heavy 300 Count

TEST DATA SUMMARY

Price per Pellet6.33 cents
Most Common Weight33.55 Grains
Pellets at That Common Weight6%
Variation in Pellet Weight (Smallest to Largest)4.0%
Most Common Head Diameter6.38 mm
6.39 mm
Pellet at That Common Head Diameter50%
Variation in Head Diameter (Smallest to Largest)0.16%
Most Common Length8.77 mm
Pellets at That Common Length16%
Variation in Length (Smallest to Largest)1.73%

 

COMPARISON TO MAKERS CLAIMS

The tin of JSB Exact King Heavy MkII 33.95 Grain .25 caliber pellets tested by HAM contained 152 pieces. This compares to the 150 claimed by the manufacturer.

Average pellet weight was 33.97 Grains. That’s just 0.6% heavier than the specification. It’s effectively right-on the manufacturer’s claim.

The manufacturer claims that these pellets are ideally-suited for long range hunting and target shooting. HAM agrees with this!

 

CONSISTENCY

No damaged pellets were found in the tin of JSB Exact King Heavy MkII 33.95 Grain .25 caliber pellets tested by HAM.

Head diameter was extremely well controlled. All measured either 6.38 mm or 6.39 mm head diameter. The difference between these two values – 0.01mm – is 0.00039 Inches.

So, all the pellets had a head diameter within just over one third of a thousandth of an inch. That’s a variation of just 0.16% in diameter. Excellent quality control!

JSB Exact King Heavy MkII 33.95 Grain .25 Caliber Pellet Test Review

 

Surprisingly, the weights of the pellets tested by HAM were less consistent that we usually find from JSB. Using HAM’s incredibly-precise, laboratory-grade milligram balance, we found a spread of individual pellet weights from 33.38 Grains up to 34.72 Grains. That’s a spread of 4.01%.

The most common weight of the tested sample was 33.55 Grains, although this was achieved by just 6% of the pellets.

Just one pellet actually matched the 33.95 Grain weight specification. However, the average weight of all the tested pellets was 33.97 Grains – extremely close to the manufacturer’s claim.

JSB Exact King Heavy MkII 33.95 Grain .25 Caliber Pellet Test Review

 

Length of the JSB Exact King Heavy MkII 33.95 Grain .25 caliber pellets tested by HAM was more constrained. The variation between shortest and longest was 1.73%, which is better than average.

16% of the tested pellets were 8.77 mm long, as can be seen from the graph below.

JSB Exact King Heavy MkII 33.95 Grain .25 Caliber Pellet Test Review

 

DIRTINESS

0.879 Grains of lead dust and junk were found in the tin of JSB Exact King Heavy MkII 33.95 Grain .25 caliber pellets tested by HAM.

Of course, some manufacturing dirt is pretty-well unavoidable in lead pellet manufacture. This amount equates to 0.586 Grains of junk per 100 pellets. That’s just under average compared to other pellets tested by HAM.

JSB Exact King Heavy MkII 33.95 Grain .25 Caliber Pellet Test Review

 

DOWNRANGE PERFORMANCE

HAM used a .25 Caliber Umarex Gauntlet air rifle for our shooting test as the standard Beeman 1074 air rifle does not have a .25 caliber barrel. And even if one were available, it would not be powerful enough…

As we can see from the Chairgun chart below, these JSB Exact King Heavy MkII 33.95 Grain .25 caliber pellets shot effectively “flat” between 10 and 38 Yards from the Gauntlet.

The high Ballistic Coeffficient is responsible for the impressive downrange performance. Even at 39 Yards, the pellet will still have a velocity 90% of the FPS at the muzzle.

 

HUNTING USE

As Chairgun shows, no less than 73% of the Muzzle Energy is retained by JSB Exact King Heavy MkII 33.95 Grain .25 caliber pellets even at 60 Yards range. This confirms the King Heavies’ suitability for long range hunting.

For HAM’s usual soap penetration test, Doug Wall positioned two blocks together to make sure that the pellet’s expected penetration could be measured. His expectation was not misplaced, as we can see from the photograph below!

The following photograph shows the fired pellet on the right, after it had been retrieved from the soap block.

The impact reduced the pellet’s length from 8.74 mm down to 8.42 mm. The dead diameter expanded from 6.38 mm to 6.52 mm as a result. The wound channel was 10 mm diameter.

This indicates that JSB Exact King Heavy MkII 33.95 Grain .25 caliber pellets would be suitable for hunting fairly large, tough critters that require strong penetration capability to ensure a humane, one shot, kill.

JSB Exact King Heavy MkII 33.95 Grain .25 Caliber Pellet Test Review

 

BUYING AND OWNING

JSB Exact King Heavy MkII 33.95 Grain .25 caliber pellets are readily available online from specialist retailers such as Pyramyd Air and Airgun Depot. As a specialist type of ammo, it’s unlikely that you will find them locally at a big box sporting goods store.

The foam disk included in the tin  – together with the inherent size and robustness of these pellets – ensures that shipping damage will be minimized in transit to you when buying online.

Note that the tin tested by HAM has the old JSB push-on lid. The company is moving to screw-top lids on a product-turnover basis, so you may find that the pellets you buy have the new, improved screw-top lids.

 

TEST DATA

JSB Exact King Heavy MkII 33.95 Grain .25 Caliber Pellet Test Review

JSB Exact King Heavy MkII 33.95 Grain .25 Caliber Pellet Test Review

For background details on HAM’s Pellet Test Review methodology, check out this link.

Chairgun is a product of Hawke Sports Optics LLC and is used with permission. Check out http://www.hawkeoptics.com

BUY FROM PYRAMYD AIR
JSB Match Diabolo Exact King MKII Heavy .25 Cal, 33.95 Grains, Domed, 300ct 0.25
BUY FROM AIRGUN DEPOT
JSB Exact King Heavy 300 Count

Understanding HAM Pellet Awards

HAM Pellet Awards come from the most rigorous, professional and comprehensive pellet testing by any independent publication. They are the result of much precise measurement and analysis using high precision measuring devices and highly-experienced testers.

Note that accuracy is a product of the complete “system” of airgun, scope, atmospheric conditions and shooter ability – not the pellet alone.

This means that no pellet test review can predict the accuracy of a particular pellet with YOUR individual air rifle. That’s why we do not measure accuracy in these pellet tests.

What HAM Pellet Awards do recognize is manufacturing consistency. Inconsistent pellets definitely will be inaccurate, consistent pellets are much more likely to be accurate.

HAM Awards also recognize value. There’s considerable variation in the price of airgun pellets. This means that an 8 cent pellet needs to score higher than a 2 cent pellet to achieve an award.

For full details of the HAM Pellet Award scoring methodology, please check out our Pellet Testing page.

For a full listing of HAM-tested Ballistic Coefficients, please see our Ballistic Coefficients page.

This entire article including scoring, data etc is Copyright Hard Air Magazine and may NOT in part or in whole be reproduced in any electronic or printed medium without prior permission from the publisher.