Some clarification to the above for the novices among us:
Assuming you are in the USA and subject to the laws of the land, it is not legal to convert a rifle to a pistol. You can shorten the barrel and remove the stock but then rather than a pistol it is considered a short barrel rifle (SBR). This is something you need to ask the federal government pretty-please with a $200 tax-stamp and other red-tape on top to be able to do legally. Then you need to figure out if a SBR is legal in your state.
I don't know but also I suspect there is a good chance the parts may have been designed to NOT interchange for that reason, I know that's something they did on the AR-7 pistol and rifle to prevent folks from just swapping parts. So even if you lived in a country that didn't care or wanted to do the federal paperwork and pay the fees, and the state you lived in would allow a SBR, you might still need a gunsmith to make some modifications.
The bad news is what you want pretty much isn't going to happen, the good news is you have a great excuse for buying another firearm!