Changing explosion size

First question, doubtless Ill have more.

I am trying to make a gun that shoots explosive bullets, and have used this to start off with:

I have switched it out to work with the smg1 and now am trying to work out how to make the explosions much smaller.

Looking at it imagnitude should change it, but even when I change it nothing appears to change. Ideally I want the explosion to change from being 8 feet tall as it appears currently to about 6 inches.

While searching for a solution I stumbled across this:
http://www.editlife.net/entity.php?name=env_explosion

But I have no clue how to put flags in.

Help?

You can’t change the size of the default explosion.

But you can make your own effect + ent.