I have a few questions about it
I have one also and need comparison

i guess noone out there owns it?

Those damn things are impossible to find, have been searching for over a year now

Where'd you get yours from?????

I did a search online for it at all online gunshops
I found a pair at a shop in the midwest...i wanted to get both of them but someone beat me to the one
so I got the other...no more exist as far as I know
they are rare and tough to find
good luck in finding one and search everywhere
just make sure you
dont get ripped off...apparently some people are selling them and marking them way up
i did find one for sale but the guy wanted about 100 dollars more than retail

I have an 870 RAS. What were you wanting to compare on the units?

how far back did you place that front slider thing?
did you ever have issues of the rail shifting forward under load/ firing...
send me pics of it installed
hell if you sell it let me know I need spare parts
I had to get a new stainless button head screw since mine stripped

We just got one in over the weekend.  Now we understand why Knight's stopped making them.  The barrel bracket is very difficult and expensive to make, and ours was out of tolerance enough that it would not fit on either of two shotguns on which we attempted to install it.  In the end, we hammered the barrel on with a brass mallet.  Dunno yet how we're going to get the barrel back off.

Have I ever had issues with the unit sliding forward under recoil? Just about every time I use it.

I don't think I have any pics of it installed anymore. There used to be some online that I posted but I don't know if they're still up or not. I haven't added pictures of weapons to any photo accounts in a long time because due to the amount of asses across the internet you have to wade through anymore I don't post that much.

Regarding the fit of the bracket onto the gun I ran into exactly the same problem that Mesa Tactical posted about. It would not fit on an 870 Express, but did fit perfectly on an older 870P.  One item of note is that in addition to this the forend of the express was too long and I wound up notching it out so t hat the action would cycle.  

Mesa Tactical as far as getting the barrel back off on mine (the express gun) I used a punch and hammer and drove it back off. Of course I'm sure that's the obvious answer.

On one of the guns when the bracket and rail shifted forward it gouged out the edge of the ejection port and never would fit exactly right after that.  I've wondered if it would help to drive some type of wedge under the bracket similar to how banded front sights are installed? Of course you've got to have just a bit of play there to get the wedge to drive into in the first place.

I likely won't sell the unit. I am going to try to possibly bend down the corner of the section that fits over the hook on the bracket to see if that will press more tightly down to keep it in place.

I'd like to close this post by saying that I see questions and "wants to buy" posts cropping up for these things in this forum from time to time.  I can honestly say that this is the worst product that I've ever seen KAC produce, and I love KAC's line of accessories.

To anyone seeking to buy this system I'd say to them avoid it (Especially with the ridiculous prices I've seen, mine was $160 new with shipping included.) You'd be a lot better off having a badger ordnance M1913 railed base attached to your receiver via drilling and tapping.  I believe Vang Comp offers this on some of their guns.

Going one step further if I were starting this project all over I'd avoid the 870 RAS and just go with a set of quality ghost ring sights.

If only the RAS worked as well as how cool it looks.....

Im beginning to agree with you and MesaTactical
I like the rail idea for BUIS because I love the fact I have an Eotech on it
the other rails justt seem to short to me because I dont like the HWS right up against my face that close...it doesnt feel right to me
I might tap and screw it to the recevier if I can figure out a good plan how to do so
Please MESA release that longer rail setup you spoke of a few months back
or someone with an old Argonaut rail sell it to me
Maybe I can screw the Mesa Sidesaddle to the rail for some support but it would
affect field stripping the damn thing
hmmmmm what about JBwelding it to the receiver ir some form of crazy epoxy
any thoughts?
ARRRGGHHHH!!!!!!!!!!!

it does have alot of cool factor with the RAS doesnt it

thats what I love about it also
Im just a dork I guess

i will get this to work somehow
even if i have to machine something or use a barrel clamp type thingie
I think i can do it

OK I think I have an Idea
How much material does the top of the receiver have on the 870P to tap and thread?
I think in order to keep my RAS from shifting it might work to tap and thread then screw the RAS to the top of the receiver
I saw a Dr Optic Mount for the top of the 870s
so I thought that idea might work
what would I need to get
any suggestions
I dont want to lose the RAS
any ideas thoughts threats suggestions
it already messed up the parkerized finish so there is no turning back on this

I'm pretty much at a loss to be honest.

is the top of the recevier ok to drill and tap?
I think i can get it to work but I dont know how much material is on top and if i drill all the way through
if it will affect the action or anything else
I have a few extra stainless screws the same length as the button head screw now
and think if i drill and tap the rear two screw holes into the receiver it will work fine along with the slider up front and ixnay the barrel clamp
my receivers finish is now fubar because of the RAS
grrrrrrrrrr

any input on this possibility

so noone has answered my question
so me in my adventurous drilling may have at least somewaht solved
the Knights 870 RAS issue for now
basically i broke the rifle down
drilled and tapped a bolt into the top of the receiver
as I had thought there was enough material to tap another screw
to help hold the RAS on top of the receiver
the current length screws I have arent quite long enough
so I need to go get more longer ones.
the only drawback is that it is a screw hole that is visible at the top inside of the ejection port
in the bolt slide action area...dirt can build up there and i need to chamfer it a bit to prevent any snagging that may occur
temporary fix probably
but at least i think it will help this build out alot
it will prevent the RAS from shifting anymore if that and hold it tighter on the receiver
pictures soon