I agree....which is why I spent the money on Troys first and found them to be too tall (and I didn't want to change the stock b/c the tube folder is so damn nice) so I ended up spending even more money on a set of HK diopters (non-folding) irons to use with an HK height LaRue Micro T-1.Don't take this wrong but you should care. To get proper eye alignment with your optics or sights your cheek weld needs to be consistant.I think the point is the XCR stockline is lower in relationship to the optical plane mounting rail than on an AR.That being the case if you mount regular AR irons you will tend to be looking low through the sights when shouldering the rifle normally.That why some XCR users are looking for lower BUIS's.Thanks for the help! Yeah, I really don't care where it sits on my cheek...just something that works Sounds like that will be easy to find!
So you either need to get lower sights or a cheek riser.All this is dependant on multiple factors,thickness of your cheek,what stock you're using,what hight scope mounts etc.The whole idea here is you don't want to have to find the sweet spot everytime you shoulder the weapon,if the rifle/aiming device mount fits you properly you will be able to consistently get into your scope or irons without repositioning.The speed gain in aquiring your sight picture being the gaol.If your mounting an optic,especially a magnified one,keep it as low as possible.
My next XCR will be using the Troys I bought, but with an RA fixed stock adapter, UBR, #2 Magpul cheek riser and probably a scope.
I just couldn't get the right sight picture with the factory folder without going to shorter irons and since every iron set I could find was for an AR except the HK, I went HK.