I just watched Pigman and he was talking about doubling the weight on his bolts by adding a bolt inside another one. It gave him a 600+ grain bolt that hit like thunder and quieted down his xbow.

Has anyone else seen this or done it? I'm assuming you have to get a smaller diameter bolt to slide inside the other bolt.

Go to your crossbow manufacturer website and see if they have a forum. Check for old threads about this subject. I know the Excalibur Forum has some threads on this subject.

A 110 grain brass inserts will accomplish the same thing.
I get mine here http://www.wyverncreations.com/index.php?main_page=product_info&cPath=90&products_id=531

You talking about crossbow arrows? Or, bolts?

That will definitely add weight, but I think they are talking about adding obscene amounts of weight. One guy mentioned using a bolt that weighed something like 660 grains.