What's the most accurate pellet in 25 caliber for Air Arms S510 XS Ultimate Sporter ?

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I've found the Air Arms Diabolo Field 24.5 grains to be extremely accurate. In the lead-free category, the Baracuda green 19.91 grains have worked best for me. I can't say that I've done an extensive comparison of pellets on a range, so take my experience with a grain of salt.

Here's a test with a .25 Sporter:

Did you means 25.4 or 24.5? I can't find any in 24.5