When assembling the bolt for the baby Barrett, you need to ensure that the final weight of the bolt and buffer is approximately 150g. 
The reinforced bolt has corresponding metal plates that can be JB welded to the breach and face surfaces of the bolt. Since JB weld can expand during curing, make sure to put some weight on top or clamp the bolt while it cures. 

After filling the bolt with tungsten powder, use JB Weld to seal that powder into the bolt. 

Make sure you sand the bottom of the bolt so it doesn’t have a sharp edge to chew up your magazine. 

EZ22 Assembly video (Baby barrett was based on EZ22)