need some help in determining how KAC rail covers fit over pic rails..sample below is pic rail with 11 ribs...2 rail covers of different lengths are shown...Question 1: due to 'rounding' of KAC rail covers, is rail cover 1 ordered a bit short to allow end of covers to slightly cover the last rib or is it ordered slightly larger so the end extends totally over the last rib (end of cover free floating)? Question 2: similar question about end length when 2 rail covers butt together..free floating ends or slightly shorter?
if someone had a photo of the back side of a KAC rail cover, it would be helpful to know exactly how the slots/ribs are counted..do you count ribs covered or slots?

Location of questions:
1______________________2
Rail Cover 1 (5 pic ribs)__________ Rail Cover 2 (6 pic ribs)
xXXXXXXXXXXXXXXXXXXXXXxxXXXXXXXXXXXXXXXXXXXXXXXXXx

(4 pic slots)______________________________(5 pic slots)

MM__MM__MM__MM__MM__MM__MM__MM__MM__MM__MM


Each MM is a Pic Rail...spaces in between MMs are Pic Slots

thanks for your help



edit: graphic didn't turn out correctly

What exactly are you trying to accomplish?  What length of rail are we talking about here?
I run KAC panels on a midlength AR, I just slide the thing on from the rear, the "locking clip" snaps in place at the back of the rail, there is a special slot in the rail for it.

You can always cut and trim a rail cover to fit your needs.



ETA:  Do these pics help at all?  These are standard KAC rails on a midlength rail system.

Jolly...as you know KAC rail covers are available in different lengths...i understand cutting is possible, but the rounded end would be lost and maintaining the rounded factory ends should reduce 'snagging' which is common on other manufacturer's square cut ends...that is why i'm getting info so that i order the proper rail cover lengths

edit: just saw your pictures..thanks..do you have a photo of the backside of the rail cover?

I'll see if I can snap a picture or two, please hold.

What length of rail are you using?  The 11 rib KAC panel will cover the entire rail on an M4/carbine style gun, measuring about 6".  On my midlength system the 11 rib panel will
leave about 2" of exposed rail.

Back of rail like this:


Or like this:

Jolly...those new pictures really helped a lot in explaining how rail cover fits over pic rails...as you mentioned (and i failed to understand), it appears the entire cover slides over the pic rails and there are no 'interior' rail/slot 'bumps' to accomodate...i'm not exactly sure how the 'clip' hold down works, but apparently it does
i'm changing out my old MagPul covers, because the squared off ends have snagged brush/carrying case/etc in the past and KACs rounded ends should cut down/eliminate this issue...the KACs are going on a DD 9.5 FSP rail and it's a somewhat odd overall length
in the very first picture you posted, the end of the pic rail is not covered...the exposed portion of the pic rail appears to be 4 full pic rails with 1/2 pic rail at the end (5 pic slots)...if you wanted to cover the exposed portion of the pic rail, which KAC rail cover would you order...a 4 or 5 rib panel? would the end of the rail cover bear on the 1/2 pic rail at the end or would it extend beyond it and 'free float' ?
thanks for your help

Correct, there are no bumps on the underside of the rail.  It's just smooth.  The locking clip locks into a certain slot in the rail, its the 1/2 pic rail that can be seen in my first picture towards the front of the gun.  There is that same special slot on the back of the rail also, which is where mine are connected.

If I wanted to cover that last bit of exposed rail I would order the 4 rib panel.  But just from mocking it up on my gun it looks like I'd have to cut it a bit.  What it would really need would be a 3 rib panel because the locking clip doesnt count as a rib (I dont think).

If I could make a suggestion, I would order two of the KAC 11 rib panels and then slap them on the rifle to see what length you'd need to fill up that extra space.  Just by putting the second one on the end to fill up that space would allow you to count ribs just to make sure you get the right ones.
Does your rail have the extensions on the side that go past the handguard cap?  If so you might be able to get away with an 11 rib and a 4 rib.

Quoted: Jolly...as you know KAC rail covers are available in different lengths...i understand cutting is possible, but the rounded end would be lost and maintaining the rounded factory ends should reduce 'snagging' which is common on other manufacturer's square cut ends...that is why i'm getting info so that i order the proper rail cover lengths edit: just saw your pictures..thanks..do you have a photo of the backside of the rail cover?

It is fairly easy to round off the cut ends.  I do it on all of my panels that get cut.