hmm, I feel as if I can help here.
I have used Crossman .20 gram BBs before.
I mean there not as bad their .12s for sure, but no where near the quality of Bastards or Metal Techs.
In my gun after about 10 rounds ill get a misfeeed (not my gun or mag, the BB's) .
Not really accurate either.
I wouldn't recommend them at all.
Although if you have to you have to, BB bastards on ASC Mart in .25 or .20 have been sold out for months (at least when I have looked).