JSB Knock Out Slugs Review .217 Cal., 25.39 Grain


Testers: Doug Wall, Stephen Archer

Caliber: .22 cal (.217)

Model Number: KnockOut SLUGS .22 217/200

Test Date: 2 May 2021

Source of Supply: Supplied by Predator International Inc.

Condition: New

We Like

Great mushrooming!
Excellent Ballistic Coefficient
Attractive price

We Don't Like

Just a little too much manufacturing variation to make a Gold Award
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



In this JSB Knock Out slugs review, we see the famous Czech manufacturer’s initial foray into this new type of airgun ammunition.

Here we have slugs that are well-priced and provide an outstanding mushrooming effect in the target. The Ballistic Coefficient is high, too. These benefits makes Knock Out slugs ideal for long range hunting use.

If your airgun’s barrel “likes” these slugs, there’s no need to look further for quality ammunition. The HAM Silver Award is definitely well deserved!


This JSB Knock Out slugs review, we found ammunition that is an excellent price for airgun slugs from a major international manufacturer.

$13.99 is the price for a 200 count tin of JSB Knock Out slugs in .22 caliber. That makes them 7 cents each.

Of course, that price can fall still further if they are purchased as part of the “buy four get one free” promotions from Airgun Depot and Pyramyd Air.

In fact, the nominal diameter for these hollowpoint “.22 caliber” slugs is .217 Inch. This slight under-sizing of diameter is typical for slug manufacturers. It’s intended to reduce the frictional effect of the long barrel contact area of slugs – many times longer than the combined head and skirt contact area for most airgun pellets.

JSB Knock Out Slugs Review .217 Cal., 25.39 Grain

JSB KnockOut Slugs .217 Cal, 25.39gr, Hollowpoint, 200ct 0.22
JSB KnockOut Slugs .217 Cal 23.39 Gr



Price per Slug7.0 cents
Most Common Weight25.40 Grains
25.42 Grains
Slugs at That Common Weight12%
Variation in Slug Weight (Smallest to Largest)1.47%
Most Common Diameter5.55 mm
Slugs at That Common Diameter30%
Variation in Diameter (Smallest to Largest)0.91%
Most Common Length8.00 mm
Slugs at That Common Length26%
Variation in Length (Smallest to Largest)1.76%



In this JSB Knock Out slugs review, we found ammunition that compares extremely well to the manufacturer’s claims!

True, this is typical of JSB products. However the comparison between the manufacturer’s specifications and this batch of slugs tested by HAM is even closer than we normally find.

Although – as we will see below – there was some variability among the individual samples in this JSB Knock Out slugs review, the AVERAGE of the slugs we tested were extremely close to the manufacturer’s specs.

For example, the average weight of the Knock Out slugs tested by HAM was 25.39 Grains. That exactly matches JSB’s specs. That’s an outstanding result which has been achieved only very rarely across all the HAL pellet and slug tests!

Then there’s the Ballistic Coefficient spec. JSB gives a value of 0.084 for this. In HAM testing, we recorded a BC of 0.086. That’s incredibly close and closer to the specs than for any other slug we have tested to date.

The diameter of Knock Outs is specified as .217 Inches. Across the samples tested in this JSB Knock Out slugs review, we found the average to be 5.55 mm. That equals 0.2185 Inches. At just 1.5 Thou difference between the average and the claim, that’s pretty close.

So, overall, these Knock Out slugs very closely match JSB’s claims for them. And yes, there were exactly 200 slugs in the tin!



The average diameter of the slugs tested by HAM (5.55 mm), was also matched by that being the most common diameter HAM Tester Doug Wall found in his PelletGage measurements.

However only 30% of the tested slugs actually had the 5.55 mm diameter. When combined with a spread of 0.91% between the largest and smallest slugs measured, it’s fair to say that we have seen ammo from JSB with more consistent manufacturing quality.

There’s a very similar story with the weight of these slugs, as is shown in the chart below. The average pellet weight was “right on the money” at 25.39 Grains. However individual pellets varied in weight between 25.20 and 25.57 Grains. That’s a variation of 1.47%.

Only 10% of the slugs measured actually weighed the 25.39 Grain average.

As always, all weight measurements were made using HAM’s laboratory-grade precision balance. This gives precise, accurate and consistent measurements.

In contrast, consistency of length was well managed. (Length is usually the most variable parameter in both slug and pellet manufacturing).

The average length of the samples measured in this JSB Knock Out slugs review was 8.01 mm. 24% of the slugs measured were of this length. The difference between the shortest and longest Knock Out slugs measured was 1.76%. Without an outlier or two, this could have been an extremely good result, as is apparent from the chart below…



Using the standard HAM washing protocol, we found 0.45 Grains of lead dirt and junk per 100 slugs.

Of course, such dirt is inevitable in the manufacture of lead airgun ammunition. However, this level of dirt is below the average for lead pellet or slug manufacture. Mostly it appears to be lead dust, as can be seen in the photograph below.



Using the HAM-generated Ballistic Coefficient of 0.086 for this JSB Knock Out slugs review, we find outstanding downrange performance – as can be seen from the Chairgun chart below.

JSB Knock Out Slugs Review .217 Cal., 25.39 Grain

As you would can see, the retained energy downrange is outstanding, with no less than 28.6 Ft/Lbs – 74% of the original Muzzle Energy – still retained at 100 Yards downrange.

Closer-in, the numbers are even more impressive! At 75 Yards, over 79% of the Muzzle Energy remains available. At 50 Yards, it’s 85.7% – 33.04 Ft/Lbs compared to the “point blank” Muzzle Energy of 38.5 Ft/Lbs.



Combined with the outstanding energy retention described above, this JSB Knock Out slugs review found limited penetration and dramatic mushrooming  too. Together, these make Knock Out slugs ideal for long range hunting.

The 50mm penetration in the standard HAM soap block test was very short for this Muzzle Energy. The 7 mm entry hole expanded into a much larger wound channel, combined with slight tumbling visible as the slug came to rest.

JSB Knock Out Slugs Review .217 Cal., 25.39 Grain

The unfired slug had a diameter of 5.55 mm. This expanded out to 9.29 mm diameter in the soap as the length compressed from 8.03 mm down to 4.84 mm.

JSB Knock Out Slugs Review .217 Cal., 25.39 Grain

That’s an increase of 2.8X in the surface area between the unfired and fired slug!

Clearly the result would be a catastrophic – and humane – one shot kill with a well-placed shot in the appropriate prey at just about any realistic airgun hunting range.



JSB Knock Out slugs are packaged in tins of 200. There’s a screw top and foam spacer included to minimize the chances of damage in transit. The HAM Team found no damaged slugs in the samples we inspected.

Although you’re unlikely to find these slugs (or, indeed any others) at your local big box sporting goods store, they’re readily available online from the usual suppliers you would expect.




JSB Knock Out Slugs Review .217 Cal., 25.39 Grain

JSB Knock Out Slugs Review .217 Cal., 25.39 Grain

JSB KnockOut Slugs .217 Cal, 25.39gr, Hollowpoint, 200ct 0.22
JSB KnockOut Slugs .217 Cal 23.39 Gr

Understanding HAM Pellet And Slug Awards

HAM Pellet and Slug Awards come from the most rigorous, professional and comprehensive ammo 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 or slug alone.

This means that no pellet or slug 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 airgun ammo tests.

What HAM Pellet and Slug Awards do recognize is manufacturing consistency. Inconsistent pellets or slugs definitely will be inaccurate, consistent ammo is 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 slug 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.