JSB Jumbo Monster Grand .22 Caliber 28.55 Grain Pellet Test Review


Testers: Doug Wall, Stephen Archer

Caliber: 0.22

Test Date: Mar 15, 2024

Source of Supply: Supplied by Predator International

Condition: New

We Like

Outstanding head diameter consistency

Excellent Ballistic Coefficient

Very clean

We Don't Like

Weights a little ragged

Nothing else


  • Comparison to Makers Claims:
  • Most Common Head Diameter
  • Variation in Head Diameter
  • Most Common Weight
  • Variation in Weight
  • Most Common Length
  • Variation in Length
  • Dirtiness



The JSB Jumbo Monster Grand .22 caliber 28.55 Grain pellets tested by HAM demonstrated outstanding consistency of head size. They were also very clean and the average weight of 28.64 Grains was extremely close to the manufacturer’s specification.

Having such a heavy weight, the Grands clearly require a very powerful PCP air rifle in order to shoot them effectively. But if that combination is available, the very high Ballistic Coefficient of 0.039 provides excellent retention of energy and velocity downrange.

In fact, during our BC testing, it was clear that these are some of the most consistent-shooting pellets we have ever tested in terms of FPS.

The Jumbo Monster Grands earn a very solid HAM Silver Award. Recommended if you have a powerful enough gun!


JSB Jumbo Monster Grand .22 caliber 28.55 Grain pellets are a new introduction from the famous Czech manufacturer. They are clearly intended as a heavier addition to the 25.39 Grain Jumbo Monster range, taking advantage of the ever-increasing power of PCP air rifles.

However the additional weight comes at a price. These new “Grands” are selling for one third more than the price of the regular Monsters. At 10 cents per pellet, the price is actually more expensive than that for some slugs of equivalent weight.

JSB Jumbo Monster Grand

So the cost of JSB Jumbo Monster Grand .22 caliber 28.55 Grain pellets is relatively high.

However – if you have a PCP air rifle that can make use of them – that will not have been a low-cost purchase either. Powerful air rifles require heavy ammo and lead costs rise accordingly.

If the Grands work well in your air rifle, they will undoubtedly be well worth the cost.

JSB Exact Jumbo Monster Grand .22 Cal, 28.55 Grains, Domed, 150ct 0.22



Price per Pellet10.00 cents
Most Common Weight28.58 and 28.69 Grains
Pellets at That Common Weight10%
Variation in Pellet Weight (Smallest to Largest)4.40%
Most Common Head Diameter5.56 mm
Pellets at That Common Diameter80%
Variation in Diameter (Smallest to Largest)0.18%
Most Common Length9.08 mm
Pellets at That Common Length22%
Variation in Length (Smallest to Largest)1.43%



The JSB Jumbo Monster Grand .22 caliber 28.55 Grain pellets tested by HAM provided an average weight of 28.64 Grains each. That’s extremely close to the manufacturer’s claim although – as is often the case – no individual pellet weighed either 28.55 or 28.64 Grains!

There were 151 pellets in the tin of Grands tested by HAM. The manufacturer’s claim is 150 pellets, so that also is good.

JSB Monster Pellets



No damaged or malformed pellets were found in the tin of JSB Jumbo Monster Grand pellets tested by HAM.

Head Diameter consistency was extremely good, as you can see from the chart. No less than 80% of the tested pellets had the same head diameter. In fact this head diameter was 5.56 mm.

The variation in head diameter between the smallest and largest pellets was just 0.18%. This is extremely good consistency.

As with other heavy pellets tested by HAM, these redesigned JSB 28.55 Grain pellets clearly achieve part of their weight though having a head diameter that’s significantly larger than the nominal 5.50 mm bore of .22 caliber air rifles.

JSB Jumbo Monster Grand .22 Caliber

Unfortunately the consistency of weight among the JSB Jumbo Monster Grand pellets tested by HAM was less good than the head diameter.

Only 10% of the tested pellets had the same weight, at 28.58 Grains, with another 10% at 28.69 Grains. The variation in weight between the lightest and heaviest pellets tested was high at 4.40%. The lightest was 28.32 Grains, while the heaviest turned the scales at no less than 29.61 Grains.

It has to be said that this weight variability matches that found in previous HAM tests of regular JSB Jumbo Monsters.

As always, the redesigned JSB Jumbo Monster Grand pellets were carefully weighed on HAM’s incredibly precise, laboratory-grade milligram balance.

Consistency was well-maintained with pellet length, however. As you can see from the chart below, 22% of the Jumbo Grand pellets tested by HAM had a length of 9.08 mm. The variation between longest and shortest pellets was fairly well-controlled at 1.43%. The longest measured was 9.15 mm long.

Note that these are very long pellets. They do fit into a Benjamin Marauder magazine, for instance. It’s possible that they may be too long for others, too, requiring the use of a single shot tray for loading, if available.

As with heavy slugs, the increased weight has to come from somewhere. Given the constraints on diameter imposed by the barrel’s bore, length is the only practical way to achieve the weight required.

JSB Jumbo Monster Grand .22 Caliber



Another strong score for the JSB Jumbo Monster Grand .22 caliber 28.55 Grain pellets tested by HAM was achieved for dirtiness. Or the lack of it!

There was a small amount of the inevitable lead dust and debris present in the tin of pellets tested by HAM. The photograph below shows the amount of dirt washed-off during our standard washing protocol from the full tin of 151 pellets.

The level of dirt per 100 pellets – the way we measure it at HAM – was 0.37 Grains. That’s below average.

As can be seen from the photograph most of this was dust. There was almost none of the relatively large semi-circular lead shavings that it’s not uncommon to find in pellet tins.



In HAM testing using our standard FX Impact air rifle, the Jumbo Grand pellets recorded an excellent Ballistic Coefficient of 0.039. This equals that of the 25.39 Grain JSB Jumbo Monsters as the highest BC value HAM has found for .22 caliber airgun pellets.

JSB Jumbo Monster Grand .22 Caliber 28.55 Grain Pellet Test Review

This Ballistic Coefficient means that the pellet retains no less than 85.3% of its original Muzzle Velocity at a distance of 50 Yards downrange.

Even out at 75 Yards, the velocity remains as high as 79.1%. That’s the benefit of the high BC!



In HAM’s standard “soap penetration test”, tester Doug Wall found that the JSB Grands penetrated 47mm into the soap block.

As we can see, the 7 mm diameter “wound channel” was straight and there was little sign that the JSB Jumbo Monster Grand .22 caliber 28.55 Grain pellet expanded hugely when giving up its energy to the soap.

The original diameter of the pellet was 5.56 mm. After carefully removing from the soap bar, the head diameter measured 5.61 mm.

The length prior to firing was 9.07 mm. On removal from the soap block, it was 8.90 mm.

In the case of this test, must be admitted that the standard Beeman 1074 breakbarrel air rifle used for this test is waaaaay under-powered for shooting the Grands.

We have made this test according to our standard protocol to enable an “apples to apples” comparison with other HAM pellets tests. However, in the expected  – much more powerful – airgun there would obviously be considerably more penetration and expansion, simply due to the higher power of the shot.



Redesigned JSB Exact Jumbo Monster 25.39 grain pellets are readily available online from from Airguns of Arizona, Airgun Depot, Pyramyd Air and more.

They are supplied in the new JSB “bayonet” top tin with a foam disk under the lid to prevent damage in transit.

There were no damaged or mal-formed pellets in the tins tested by HAM. The thick, shallow skirts and tight packaging in the tin mean that damage in transit is relatively unlikely to occur. You – the user – benefit from a very high percentage of usable pellets in the tin.



JSB Jumbo Monster Grand .22 Caliber

JSB Jumbo Monster Grand .22 Caliber

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

JSB Exact Jumbo Monster Grand .22 Cal, 28.55 Grains, Domed, 150ct 0.22

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.