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Posted: 3/2/2007 9:11:17 AM EDT
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I posted this question in the "upper" thread as well. I am obtaining a Stag 6.8 left hand model. This AR comes in carbine length. Can a mid-length rail fit onto this platform? Does it affect gas block positioning? One option would be to keep the standard front site and get a rail that extends beyond the site. Another option would be to get a flip site that fits on the gas block or rail. Just not sure how any of this can be configured. Stag only has the carbine length rails in stock and some of the LaRue rails in mid-length look like what I want for my 6.8 configuration. Any input would be greatly appreciated. Daryn |
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Yes, you could use a LaRue mid length rails as long as you replace your FSB with a LaRue low profile gas block (recommended) or any brand low profile gas block. You could use the LaRue 9.0 or if you don't mind a little extra weight but would get more sight radius, the longer LaRue 10.0 should also work. I have a mid length gas system barrel with a standard FSB with LaRue 9.0 which I built the upper myself. |
Yes, I'm sure the LaRue low profile gas block would fit their own rails but other brands of low profile gas blocks should also work. You could even get a 12" or longer rails and it would still work but would be slightly heavier than the 10". Make sure you get a rail mounted flip up backup sight model for your rail and not a gas block sight mounted model, they're two different sizes, the gas block mounted sight is longer that the rail mounted sight. |
 Here's a photo of my 16" carbine with a LaRue 9" rail, since you won't have the fixed front sight try to ignore it in my picture. If you still think that there's too much barrel sticking out of the 9" rail, the 10" is still not bad. I've seen guys that got 12" and 13.2" long rails, in my personal opinion that's way too much for general use unless you use it for competition. 
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I have a mid length gas system barrel and my standard front sight base is my gas block, no low profile gas block at all. My LaRue rail installation went real smooth except installing the front sight base with taper pins was a pain in the a$$.
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If you want to use a 9" rail on a carbine length barrel you need to remove the fixed FSB and put on a low profile gas block. It will go under the rail. Than you will need to buy a new FSB that will attach to the rail. But there are a few companies that sell 9" rails for Carbine lenth systems, they have a cut out on the top for your FSB to go through. Then you can keep your fixed FSB if you want. |
If you want to use a 9" FF rail the original FSB have to be removed and replaced with a low profile gas block. If you want to use a standard FSB as just a front sight instead of a rail mounted backup iron sight, the barrel in front of the handguard have to have a diameter of .750" in order to fit a standard FSB. Then it have to be drilled through the FSB and barrel and taper pinned or if not drilling for pins, a set screw could be used to mount the FSB. In your case with the Stag 6.8mm barrel the area in front of the 9" rails might not be .750" diameter, it might be smaller like .740" or less. To mount a standard FSB with .750" diameter hole on a .740" or less barrel diameter, either a shim or collar could be custom made or make a custom FSB with a .740" hole. You could either do it yourself or have someone like Randall of AR15Barrels.com could make it for you. I think it's much easier to just get a rail mounted front sight than to custom fit a standard FSB to your 6.8mm barrel. |
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