Is 500g @300SRM = 250g @600SRM

[BandonBrewingCo]

Title says it all really. Are crystal and dark malts subbed in a linear fashion?
Is 1kg 20SRM = 2KG 10SRM?
Or is it just with the roasted barley where I have to be extra careful? Is there any guidelines on this (especially for roasted barley)?

 

[Queequeg]

Above the taste fresh hold the answer is no. Special B won't ever taste like crystal 60 regardless of quanity. The same is true with roast malts.

Below the taste fresh hold its a bit more complicated because wort colour is not a linear scale. For colour adjustments just used brewing software to derive the colour you want base on the quanity and Colour of additions.