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Posted: 3/28/2014 1:09:01 PM EDT
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Alright folks, while bouncing around the forums I have seen a lot of people who either were against KeyMod, didn't understand it or loved it but were having issues attaching accessories. so I thought I would throw together a write up with some photos. Please do not think that because I am doing a write up that KeyMod is complicated, because it is not, in fact it is probably simple enough that some folks are over thinking it.
KeyMod is obviously a larger hole that is connected to a smaller, longer slot with a half circle on the muzzle end. The photo below shows the proper orientation for the backer nut in relation to the KeyMod slot. 
This allows for the backer nut, which I am going to refer to as the shoe because that is exactly what it looks like, to slide in then forward as far as possible so that the shoe rests in the machined slot that it is made to fit into. There should be no gap or space between these pieces. If is in backwards like the photo below it causes a slight space between the edge of the shoe and the end of the KeyMod slot, which you can see in the next photo. This causes an issue with your accessory not locking in correctly and having the ability to slide loose. This has been the issue with several of the QD cup sling mounts I have seen in regards to improper installation. 
Like I said earlier the shoe should fit snugly down into the slot, this fit combined with tension is what serves as a backer. If you allow your shoe to be too loose before fitting it into the handguard you are using it can become crooked and even though it feels tight as far as torque wise it is just resting on the edge of the slot it fits into and not doing a thing for your tension. This can cause slipping and wiggle also and is hard to see due to how tight most of these handguards fit to the barrel. 
In addition to the shoes and screws for tension every KeyMod accessory piece I have had my hand on has had some sort of lug that rests in the back of the large slot between the two screws or forward of the front tension screw. These lugs contact that larger hole in the KeyMod slot and make it so the accessory can not slide backwards. If this lug doesn't do that you do not have your accessory installed correctly. This photo shows a properly torqued shoe and screw, the lug directly behind it and then in the back is a shoe that is loose, facing correctly (rounded piece towards the muzzle) 
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Quoted: Not sure if sarcasm? I was actually asked to do this by some folks that sell these accessories everyday and every single day get a ton of calls asking why their accessory isn't lining up or locking in. Very good write up BTW as I was trying to reverse my handstop and it would not work until I figured I had to reverse my backer as well. People really are over thinking this.
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Yes, because putting a backer plate on in the middle of the handguard is really easy... Quoted:
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Id rather have a simple "screw on" system like a cmr or evolution. More straightforward Yes, because putting a backer plate on in the middle of the handguard is really easy... CMRs don't need backing plates. 
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CMRs don't need backing plates. Quoted:
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Id rather have a simple "screw on" system like a cmr or evolution. More straightforward Yes, because putting a backer plate on in the middle of the handguard is really easy... CMRs don't need backing plates. This^ |
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This^ Quoted:
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Id rather have a simple "screw on" system like a cmr or evolution. More straightforward Yes, because putting a backer plate on in the middle of the handguard is really easy... CMRs don't need backing plates. This^ True, but Evos do... |
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