I may be incorrect on this, in which case I am sure you guys will set me straight, but I thought Varget was to be used for heavier bullets and longer barrels. For example, it is typically used with 70 to 80 gr bullets in 20" service rifle barrels (or longer).
I'm not saying it won't work (it will), I'm just asking that you consider whether you picked the right powder for the light bullet and very short barrel you plan to use.
Why did you buy just one pound? Is this just for load development? Why go through the trouble to develop a load when you only plan to use one pound of powder? If the pound is only for load development, then you know you need to use a range of powder charges to determine which is best. So, you can tell I am a little bit confused about where you are going with this.
One way to deal with your original question is this. Fill a resized case with powder untill it reaches where the base of the bullet will be when seated to your intended OAL. This will determine the approximate powder charge your case can hold without being compressed. The reason I suggest this, as a test,... a reality check,... is that I don't think you can get 27.5 gr of Varget in a case and still seat the bullet to the intended depth.
Develop your own load. Start low, not high. Work your way up. Be safe!
I hope this helps.