bitmap - Converting colorspace in Imagemagick is not working -

i trying convert srgb bitmap file greyscale using imagemagick. i've tried using convert -set colorspace gray , convert colorspace gray, according documentation should it. however, when try check output file using

identify -format "%[colorspace]" <outputfile> 

it still tells me in srgb. aware not file formats support colourspaces, , tried converting bitmap png first, changing colorspace , converting back. identify acknowledged png in gray colorspace, reverted srgb when reconverted bitmap.

i have tried using -profile option change colourspace, not seem work. i'm not bitmap files can accept profiles? should add have no way apart using identify tell whether colourspace changes have been applied; actual images greyscale already, trying prep them use program not accept colour bitmaps, true greyscale.

has else had issue? thanks!