Are all Steel BBs the same?

There are a range of different weights of 6mm BB available which means it’s possible to experiment to find the one that suits a particular replica perfectly. There is also a notable difference in the quality of different brands of 6mm BBs. But, all 4.5mm steel are the same? Aren’t they? There’s only one way to find out for sure…


For those of us who shoot with 4.5mm steel BBs, we don’t have the option of trying different weights of BB to see which is best as all steel BBs are claimed to be identical. Likewise in terms of quality – there aren’t supposed to be notable differences between brands. But, is that really true? To find out, I thought I’d head-to-head test three different brands of 4.5mm BB to see if there are detectable differences in power and consistency of shooting. So, let’s try to answer the question: Are all steel BBs the same?

The Test

All steel BBs have a nominal diameter of 4.5mm and a weight of.35g. These are sometimes also referred to as .177” caliber. This is technically incorrect though these 4.5mm steel BBs can be shot through a rifled, .177” barrel.

Up for this test I have three different brands of 4.5mm steel BB, These are:

  • Umarex steel BBs, which are identified as 5mm, (.177)
  • ASG Blaster steel BBs which are identified as 5mm/.177”, 0.35g
  • Heckler & Koch black coated steel BBs which are identified as 5mm (.177)

Heckler & Koch Steel BBs


With their distinctive semi-matt black finish the H&K BBs certainly look different, but when you look closely, even the Blaster and Umarex BBs aren’t quite the same. The Umarex BBs are slightly darker in colour and look a little more shiny than the ASG BBs.

ASG Blaster steel BBs


This is interesting because I had wondered whether the ASG and Umarex BBs were simply re-branded versions of the same thing, but they certainly do look different.

Umarex steel BBs


The first thing I did was to weigh these BBs and this confirms that the ASG and Umarex BBs are precisely 0.35g while the H&K BBs are marginally lighter at 0.34g.

Power test

For this part of the test I shot ten of each type of BB over my chronograph and produced an average figure from the results. To try to produce consistent results, these tests were done using the same replica, at the same time and in the same location and with fresh CO2. In each case, I waited five seconds between shots to avoid issues with cooldown. And the scores on the doors were (all power measurements are in fps):

ASG Blaster steel BBs












Giving an average speed for the ASG Blaster BBs of 264.7 fps

Umarex steel BBs












Giving an average speed for the Umarex BBs of 270.3 fps

Heckler & Koch steel BBs












Giving an average speed for the H&K BBs of 273.7 fps

Now, you’d have to do a great deal more testing to be certain, but it does seem that there is a small but measurable difference in the average speed at which each type of BB is fired. The H&K BBs fire with a little more speed than the Umarex and ASG BBs, but then they are fractionally lighter, so perhaps that’s why? However, that doesn’t explain the differences between the Umarex and ASG BBs. They’re both the same weight, though the Umarex BBs do seem more shiny – perhaps they have a smoother surface finish and that gives a small boost in fps? While testing this particular replica it did seem that generally the ASG BBs gave speeds in the lower 260s, Umarex BBs gave speeds in the upper 260s/lower 270s and the H&K BBs gave speeds in the lower 270s. Is that significant if you’re target shooting? Not really, but it will be interesting to see how this translates into the next part of the test, accuracy and consistency.


For the shooting part of the test, I shot several ten shot strings at targets at 6m range with the replica in a rested position. As before, I changed to a fresh CO2 before changing ammo type and I should note that the replica I used for the test has a tendency to shoot low and the aim point for all the targets shown below was the centre point of the black circle. Obviously there’s always going to be a degree of the human element in a test like this, but here’s what I found.



10 shots, rested, 6m, H&K Steel BBs

The H&K BBs typically produced groups of around 1.25 – 1.5” horizontal spread and 2 – 2.25 vertical spread. Groups were centered around 1.25” below the point of aim.

ASG Blaster BBs


10 shots, rested, 6m, ASG Blaster BBs

The ASG Blaster BBs typically produced groups of 1.5 – 1.75” horizontal spread and 2.25 – 2.5” vertical spread. Groups were centered around 1.75” below the point of aim.

Umarex Steel BBs


10 shots, rested, 6m, Umarex steel BBs

The Umarex steel BBs typically produced groups of 1.25” horizontal spread and 1.5” vertical spread. Groups were typically centered 1.75” below the point of aim.

During the test, it was notable that the Umarex steel BBs consistently produced the smallest groups. The difference between these and the other BBs wasn’t huge, but it was measurable and consistent. The H&K and Blaster BBs produced similar sized groups, but the groups produced by the H&K BBs were centered around 0.5” higher than the groups produced by the other two types.

So, overall and based on this testing, I’d have to say that if you want the consistently smallest sized groups, I’d recommend the Umarex steel BBs. However, if you have a 4.5mm replica which shoots low, you may want to try the H&K BBs as these do seem to produce groups that centre a little higher than the other two,


The differences I found during this part of the test are fairly minimal, and certainly nothing like the differences that can be seen between different types of 6mm BBs (for example, some Chinese-made 6mm BBs are essentially unusable). However, there do seem to be differences here. The H&K BBs appear to produce a group with its centre around ½” higher than the others at a range of 6m, which could be useful if you have a replica that shoots low with other types of BB. The Umarex BBs did seem to produce groups that were consistently smaller than those produced by the other two types.

So, there you are. Are all steel BBs the same? Not quite, it seems, though there are no huge differences. However, these are significant enough that, next time I’m buying steel BBs, I’ll probably go for Umarex steel BBs if they’re available and H & K BBs if I’m using a replica that shoots low.

Like everything else that I publish here on the World of Replica Air Pistols, I have tried to be objective and unbiased here. However, for the sake of consistency I used a single replica during testing and it’s worth pointing out that it’s entirely possible that, if you use a different replica, you may get different results.

Happy shooting

Related pages

Shooting stance

How to make your replica shoot more accurately

Technical articles

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