Air Arms S510XS
Air Arms S510XS Ultimate Sporter with Laminate Stock.

Part 1
Part 2
Part 3
Meopta MeoPro Optika6 3-18X56-scope: Part 1
Part 4
Part 5
Part 6
Part 7
Part 8

This report covers:

  • Background
  • The test
  • Air Arms 16-grain dome
  • First group
  • H&N Baracuda 15
  • Air Boss
  • Is BB shooting his best?
  • Discussion
  • Summary

Today’s report is really another test of the Apolo Air Boss .22-caliber pellet. But as Pyramyd Air doesn’t carry the Air Boss pellets yet, I put it under the Air Arms S510XS Ultimate Sporter with Laminate Stock.


The S510XS is the most accurate .22 caliber precharged pneumatic (PCP) that I own, so I use it as a testbed. It mounts a Meopta MeoPro Optika6 3-18X56 scope with an illuminated reticle. When I got ready to shoot I discovered that the scope’s CR2032 battery had gone dead. I try to remember to turn off the scopes with illuminated reticles and this is a note to myself that I did indeed turn it off after today’s test.

I also didn’t bother sighting-in because the scope was already on at 25 yards in my December test of Baracuda pellets then and now. It was sighted low and to the right to preserve the aim point. They might have hit just a little lower today than they did then, but I did not adjust the scope.

The test

I shot from 25 yards with the rifle rested directly on the sandbag. I will have more to say about the rest in a bit.

I shot 10-shot groups with every pellet. After the smoothness of the TX200 Mark III with the Tony Leach kit it was a surprise that the S510 wasn’t as stable on the sandbag. More on that in a moment. Let’s get started.

Air Arms 16-grain dome

In the past the Air Arms 16-grain dome has been the most accurate pellet in this rifle. Back in October of 2019 this rifle put 10 of these pellets into 0.18-inches at 25 yards. In Part 8 of this report ten of the same pellet made a 0.193-inch group at 25 yards. I felt this was the right pellet to use as a baseline for today’s test.

First group

Unfortunately while shooting the first group I discovered that the S510 isn’t as stable on the sandbag as my TX200. It’s so tall that it’s top-heavy. The first group was larger than I would have liked as a result. Ten Air Arms 16-grain domes went into 0.486-inches at 25 yards. Look at the group. The first shot went high and to the right and shot number seven went low and right. The other 8 shots are in a tighter group that reflects the pellet’s true accuracy in this rifle, but it doesn’t matter because those two shots messed it up.

Air Arms S510XS-AA-16-group1
This group of 10 Air Arms 16-grain domes measures 0.486-inches between centers.

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H&N Baracuda 15

The next pellet I tested was the new H&N Baracuda 15 that was the second best one in my test of Baracuda pellets then and now. It was only a little less accurate than the Baracuda 18 pellet, grouping 10 in 0.322-inches at 25 yards.

This time I adjusted the hold of the rifle by sliding my shooting hand forward until it was pressed into the rear of the sandbag. This was a more stable hold, though not as stable as the TX200 in that recent test. Still, I was able to keep the illuminated dot over the bullseye central dot most of the time. But by the end of this report I will prove to you that this is indeed a more stable hold.

Air Arms S510XS Barracuda 15 group
Ten Baracuda 15 pellets made this 0.329-inch group at 25 yards. Now we’re cookin’!

Air Boss

Now for the group that this whole test is about. But before we look at the group, so many of you asked whether these pellets are hard lead or soft that I did the very unscientific fingernail test. The pellet was scratched by my fingernail. In my opinion it is dead soft.

And what about the accuracy, now that BB is shooting his best? Ten Air Boss pellets went into a very round group that measures 0.478-inches between centers.

Air Arms S510XS-Air Boss group
When the rifle was held steady ten Air Boss pellets went into a very round 0.478-inch group.

Is BB shooting his best?

Okay I said I would get to this. I knew the Air Arms 16-grain domes were more accurate than we saw in the first group. So I shot another group of them. This time ten made a 0.241-inch group at 25 yards. That is the best I could do on this day, folks.

Air Arms S510XS AA 16 group
And here is the proof that I’m holding the rifle in the best way. Ten Air Arms 16-grain pellets made this 0.241-inch grouip at 25 yards.


Today the Air Boss pellet made the largest group of the three pellets tested. The other two pellets were known to be good in the S510, so my conclusion is the Air Boss isn’t quite as good in this rifle as either of them.

In the test with the Dragonfly Mark 2 the Air Boss was the second best pellet tested. And from that, plus what we see today, my conclusion is that the Air Boss is a good pellet that will vary from airgun to airgun.

Two tests hardly establish anything, but they do point us in a direction. And that direction seems to be that the Air Boss is a good pellet. I want to try one more test with these pellets in the Sig ASP20 breakbarrel. I only got a few Air Boss pellets in each caliber, perhaps 40-50 or so, so my testing of them is limited.


It was nice to see some new pellets at the SHOT Show, and I still have both .177 and .25-caliber Air Boss pellets to evaluate. We will look at all of them over the coming weeks and months.