Get yourself a C&R liscense for $30.00 / 3 years. Then you can buy your 922r parts & other supplies at big discount from Brownells, Midway. Numrich, Century, etc.
Parts kits are too few & far between for group buys I think. Plus postage is so damn crazy high, that the savings is lost in re-packaging & distributing the item.
Again, just my opinion.