First, there are no aftermarket hammer packs.Ok someone please explain to me why they are going for so much money? I am 99% sure I have a gen 1 hammer pack and I don't understand why the price? What would be the disadvantage of me selling mine for outrageous money and buying a good aftermarket trigger pack? Inquiring minds want to know. Also, how would I verify I do indeed have a gen 1 pack?
Previously I saw the FS2000 Gen 1 hammer groups going for $450-$600 on GunBroker.
Be aware that the F2000 (military select fire) and FS2000 have different dimensions on the hammer group, and are not interchangeable.
I hope your friend is an 07/02 SOT FFL. They are not supposed to be interchangable without modification. Like the PS90, you can not put a P90 hammer group in it without modification. The stock will not allow it without modification. It's supposed to be the same with the FS2K/F2K series.