strait 20 fan here
they are only a little longer than the 10 round but don't get in the way with my arm in prone a little more to grip when changing mags
X2 on this. I carry 20s for both hunting and target shooting.
PS If you ever see me packing 30s better grab yours too, things done gone south and I felt 20 was not enough.
I also learned the hard way don't load them full
down load by at least one got up in the tree stand one morning and put mag in and try and release it easy I can tell there is a deer in the dark 50 yards out form my stand bedded down. had a full mag , BCG hung up on the first round then after what seemed like forever but was probably only 20 seconds it slammed forward deer got up and moved in the dark , luckily not too far and come fist light he was circling behind me.
don't load any ar mags full any more max of 19 in a 20 , 29 in a 30