The HW variants give approx:
.177 carbine: 4 mags
.177 full length: 8 mags
.22 carbine: 5 mags
.22 full length: 10 mags
Most will be close to the above, but it varies a little from one gun to another, depending on whether you get a good one (might give 5-6 mags in .177K) or a bad one (might give 2-3 mags in .177K).