sulli90
02-02-15, 19:17
I wanted to get this out there in the event, someone somewhere in the future has the same problem as me. It might save some confusion.
Let me preface all this by saying, it is possible I may have the only gun in existence with this issue. Seems unlikely to me, but this is the first I've heard of it. And from talking to Larue, they've never had anybody contact them with this issue.
This all starts back in Oct. 2014. I had recently finished building a LR308, starting out with a JD Machine matching upper and lower. I was excited about my first 308 and decided to go with an ACOG (TA11J-308G) as the optic, also a first for me. I looked around and decided to get it from Larue as a package deal with the LT100 mount.
Flash forward 3 months and it arrives, I'm jumping up and down with excitement to finally get this thing going.
I attach the ACOG to the mount, loctite it, mount it to the rifle, and went to sight it in. I returned and started the cleaning of my rifle, starting by removing the ACOG. To my surprise, there were two indentions into the top of the rail. It was clear that the 2 screw heads holding the ACOG to the mount were contacting the rail. I'm crushed, did I do something wrong? I've attached a picture of the rail and a picture showing the wear on the screw heads. It should be noted that the screws were properly installed. They are not bottomed in the ACOG, they are not cross threaded, they are fully torqued and as deep into the mount as they can be.
As I start to study the mount, I'm surprised to see that the screw heads are not completely recessed like the factory Trijicon mount. They are actually partially exposed (see pic of the screw head protruding from bottom side of mount). I chalked this up to an issue with my mount, the recess for the screw heads must have not been countersunk enough? I talked to Larue and they had me return it for them to inspect.
A couple days I get a call back, there no problems with the mount, it is within there spec. There is supposed to be a gap between the bottom of the mount and the top of the rail, the exposed screw heads shouldn't be an issue. I ask if anything else could have caused it, Larue says either something is wrong with the rail or the heli-coils in the ACOG are causing the screws to bottom out early. So I decided to send the ACOG to them for inspection. I have a Centurion CMR rail on my 308 and I remembered the two picatinny rails lined up perfectly, I couldn't see the rail on the upper being an issue?
Well, I was out of town all that week and wasn't able to send it out. That weekend I get back and take one of their LT104 mounts and compare to my 308 and two Colts. Sure enough I can see that gap Larue is talking about. However that gap is much tighter on the JD Machine upper, about just enough to slide a thin piece of paper in. I bust out a micrometer and go all over the 3 rails. It seems that the JD Machine upper rail is slightly "beefier" than the Colts. Is it out of spec? I have no idea.
I call back Larue and inform them I think I know what is going on now. Their mount with exposed screw heads is not going to work with this rail. I need a mount that is like the factory Trijicon one, which works perfectly on this gun. Unfortunately, I had shot the gun so I couldn't get a refund on the Larue mount, it is headed back to me. I've placed an order for a mount from a different manufacturer, I've been assured the screw heads are not exposed. It should be no different than the factory mount except with QD capabilities.
Moral of the story, if you going with a LT100 be sure you are not one of those people with a "beefier" rail. I personally think it is a flaw to not completely recess the screw heads (which would prevent the problem), but obviously something is going on with my rail to cause that tolerance to be tighter. And clearly, this must not be a very common thing, can't find any other record of it happening. I love all my Larue products, but unfortunately I'm going to have to do something different for this gun.
Sorry for being longwinded, hopefully this helps somebody in the future.
Let me preface all this by saying, it is possible I may have the only gun in existence with this issue. Seems unlikely to me, but this is the first I've heard of it. And from talking to Larue, they've never had anybody contact them with this issue.
This all starts back in Oct. 2014. I had recently finished building a LR308, starting out with a JD Machine matching upper and lower. I was excited about my first 308 and decided to go with an ACOG (TA11J-308G) as the optic, also a first for me. I looked around and decided to get it from Larue as a package deal with the LT100 mount.
Flash forward 3 months and it arrives, I'm jumping up and down with excitement to finally get this thing going.
I attach the ACOG to the mount, loctite it, mount it to the rifle, and went to sight it in. I returned and started the cleaning of my rifle, starting by removing the ACOG. To my surprise, there were two indentions into the top of the rail. It was clear that the 2 screw heads holding the ACOG to the mount were contacting the rail. I'm crushed, did I do something wrong? I've attached a picture of the rail and a picture showing the wear on the screw heads. It should be noted that the screws were properly installed. They are not bottomed in the ACOG, they are not cross threaded, they are fully torqued and as deep into the mount as they can be.
As I start to study the mount, I'm surprised to see that the screw heads are not completely recessed like the factory Trijicon mount. They are actually partially exposed (see pic of the screw head protruding from bottom side of mount). I chalked this up to an issue with my mount, the recess for the screw heads must have not been countersunk enough? I talked to Larue and they had me return it for them to inspect.
A couple days I get a call back, there no problems with the mount, it is within there spec. There is supposed to be a gap between the bottom of the mount and the top of the rail, the exposed screw heads shouldn't be an issue. I ask if anything else could have caused it, Larue says either something is wrong with the rail or the heli-coils in the ACOG are causing the screws to bottom out early. So I decided to send the ACOG to them for inspection. I have a Centurion CMR rail on my 308 and I remembered the two picatinny rails lined up perfectly, I couldn't see the rail on the upper being an issue?
Well, I was out of town all that week and wasn't able to send it out. That weekend I get back and take one of their LT104 mounts and compare to my 308 and two Colts. Sure enough I can see that gap Larue is talking about. However that gap is much tighter on the JD Machine upper, about just enough to slide a thin piece of paper in. I bust out a micrometer and go all over the 3 rails. It seems that the JD Machine upper rail is slightly "beefier" than the Colts. Is it out of spec? I have no idea.
I call back Larue and inform them I think I know what is going on now. Their mount with exposed screw heads is not going to work with this rail. I need a mount that is like the factory Trijicon one, which works perfectly on this gun. Unfortunately, I had shot the gun so I couldn't get a refund on the Larue mount, it is headed back to me. I've placed an order for a mount from a different manufacturer, I've been assured the screw heads are not exposed. It should be no different than the factory mount except with QD capabilities.
Moral of the story, if you going with a LT100 be sure you are not one of those people with a "beefier" rail. I personally think it is a flaw to not completely recess the screw heads (which would prevent the problem), but obviously something is going on with my rail to cause that tolerance to be tighter. And clearly, this must not be a very common thing, can't find any other record of it happening. I love all my Larue products, but unfortunately I'm going to have to do something different for this gun.
Sorry for being longwinded, hopefully this helps somebody in the future.