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Discussion Starter · #1 ·
This Knights MK12 mod I rail was installed ( my guy is usually good to go) about a half inch off center. The clone correct kac rear sights have to be set all the way left and I still have to aim a touch left to impact on center. The peek sights are the same way. An optic on the upper has no issues. I really don’t want to send it back to get fixed and I can’t sell the upper as is, so is there a home remedy for this?
Thanks
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The only thing that could be off is where your smith put the pins in the barrel nut. You can unscrew the rail collar, than pull the rail off, and check where the two pins are set. The pins are what keep the handguard from rotating.

Also can you post a picture looking straight down the receiver and rail section?
 

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I am not familiar with that rail, but a 1/2" error is pretty bad mistake to make. Have the gunsmith replace the rail and modify it correctly is the right thing to do.

A home remedy is to shim the front sight by bending a "V" shape shim to put on the side of the rail. I have made a few to fix the same issue by using a piece of air condition duct material cut to size. and then bent in to the "V" shape. A thin bead of silicon can keep it in place until you get the sight installed and tightened down. I use a chamber laser to bore sight, and the goal is to get mechanical zero on the rear sight with laser on the target center. You might have to try different thickness shim material to get close to MZ. Minor adjustments can be done with a thin shim like a soda pop can. This fix works for clamp design sights like KAC, but do not work with Magpul Gen 2 style polymer that slide on the rail (it's to tight to slide the sight and get the shim on the rail too).

Hope this gets you started, PM me to set up a phone call for more detailed instructions.
 

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Discussion Starter · #5 · (Edited)
I didn’t know you could unscrew that thing. I thought Knights required a special wrench for the MK12 rail. I’ll try that out with the pins. Each pin clockwise adjusted one slot should do it. Thanks
Edit - Maybe it’s one pin counterclockwise. Maybe two.
End Edit
The fixed sights (my preference) are Scalarworks Peak Sights. The KAC BUIS also have to be set far left to sync with desired point of impact so it’s definitely the rail.
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I didn’t know you could unscrew that thing. I thought Knights required a special wrench for the MK12 rail. I’ll try that out with the pins. Each pin clockwise adjusted one slot should do it. Thanks
Edit - Maybe it’s one pin counterclockwise. Maybe two.
End Edit
The fixed sights (my preference) are Scalarworks Peak Sights. The KAC BUIS also have to be set far left to sync with desired point of impact so it’s definitely the rail.
View attachment 381695 View attachment 381697 View attachment 381699

Ok, that answers the sight conundrum, pics didn’t match the description.

Put a straight edge on the 45* angle of the upper receiver. How far off is the rail?

who installed the rail?
 

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Discussion Starter · #9 ·
The guy is well known on related sites but when I sent him the Colt upper to have the gas block and rail attached I forgot to send the BCG and request a test firing. He mailed it back before I realized.
This drawn out video is pretty much how to install it:
I’ll probably send it back to him and restore it to it’s simple stature. Probably have it cut down to an sbr too boot.
 

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Discussion Starter · #14 ·
Yep......I know all about installing the Knights rail. Its really just about idiot proof for an install. What receivers are you using?
Never heard of that guy before. Have you spoken with him about the issue?

Use a straight edge as I said and see how canted the rail is
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I haven’t spoke to him yet but I’m waiting for my approval on the Knights lower and then I’m going to have him cut the 6721 barrel down and restore the Colt upper to its original configuration (minus the 1.5). I was thinking about getting a cqb upper and keeping this quasi MK12 mod I and that’s why I was inquiring about the fix but now I’m thinking I’ll send it back I’ll just go old school with the upper. Carry handle and all. Now I need to find an AF carry handle.
 

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Discussion Starter · #19 ·
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So, what was the verdict ?
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At the range at this very moment. The target is @ 100 yards. These holes are Wolf Military Classic at somewhat rapid fire with the Scalarworks Peak Sights.I picked a spot just left of the paper. Checked the impact. Was satisfied. Popped of 19 more rounds in about 15 seconds. Good enough. The covered up shots on the right were AE XM193. Slow fire. Aimed at the middle. The upper is a Colt 6721 16” 556 NATO @ 1-9.
63 degrees. 18% humidity. 5 mph wind form right to left. 3,700’ elevation.
I’m just going to roll with what I got. It’s consistent once you have point of aim (same point as it has been for the two months I’ve been using this) and an optic on the upper is true.
 
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