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Posted: 1/27/2010 1:35:08 PM EDT
I recently purchased a SWS e1 rail for my DPMS lr-308 build and to my surprise the hand-guard rail sits way higher then the rail on my upper.  Any idea's to why the difference in height?
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You will find variance on upper receiver rail heights from the 7.62 AR manufacturers since there is no standard as there is with the 5.56 platform. Thats not just between the brands but also within the brands from one batch to the next. Those variances will range from a few thousands to .020 or more!!! And, yes that is true even with the high dollar offerings out there. SWS did their best to draw a happy medium but unfortunately, they cannot match everybody perfect.
Note: I am not associated with SWS in any way, but I have used many of heir rails on .308's and I have never found variance in their rail height. |
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I had the same isssue. I purchased a lr308 upper from midwayusa installed a pri free float tube and the rail was to tall just as in the pic. Sent the pri tube back purchased a sws e1 rail and installed it same thing the rail was to high. It turned out it was the receiver itself I guess dpms changed them awhile back. The upper I got from midway was complete with forward assist. I had a fellow arfcomer measure his lr308 upper to see if mine was off and it was. Sent the upper back to midway. Then purchased one from fulton armory, when i reinstalled the sws e1 rail everything lined up perfect.
long story short its your receiver not the rail |
| It might not look like a big difference in sandsleep pic. But it bugged the hell out of me. I think the newer dpms upper receivers are taller because you see alot of builds with dpms receivers and everything look the right height. But I will stick with fulton or another brand. |
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Our AR15 receivers are all the same height except the High Rider and Tri-Mount. I wonder if that's what Mark was thinking of in his reply.
The LR308 Platform has two heights, the A3 and Lo-Pro Raised Rail. The A3 was changed recently to better accommodate our other components. I guess in reality, with the number sold before the change, there are now 3 heights. To find out if you have a newer model or older run, the easiest way to measure is with a caliper from the bottom surface that mates to the lower to the top of the rail. The new versions measure 2.003 and the old versions are 2.063. Any larger receiver rail to handguard rail height difference would be due to the lack of an industry standard in the large frame AR style rifles. Everybody is still pretty much making their own thing and some measurements just don't line up between manufacturers. |
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My LR-260 (definitely new production) measures 2.007". My LR-308C (built within the last 3 months) measures 2.0035".
My 308C has a Daniel Defense 7.62 LIte Rail 12.0 which is taller.....but very hard to accurately measure how much taller. Is there an existing rail that matches up with the new A3 receiver? Hey Sniperx, what rails do you make? Grizz |
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My LR-260 (definitely new production) measures 2.007". My LR-308C (built within the last 3 months) measures 2.0035". My 308C has a Daniel Defense 7.62 LIte Rail 12.0 which is taller.....but very hard to accurately measure how much taller. Is there an existing rail that matches up with the new A3 receiver? Hey Sniperx, what rails do you make? Grizz http://www.superiorweaponssystems.com/index.html Not to mention most of the rails Noveske uses 
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My LR-260 (definitely new production) measures 2.007". My LR-308C (built within the last 3 months) measures 2.0035". My 308C has a Daniel Defense 7.62 LIte Rail 12.0 which is taller.....but very hard to accurately measure how much taller. Is there an existing rail that matches up with the new A3 receiver? Hey Sniperx, what rails do you make? Grizz http://www.superiorweaponssystems.com/index.html Not to mention most of the rails Noveske uses Excellent. I went back and forth quite a bit on which one to start with for my 308.....DD or SWS. I finally decided to put a DD on my 308 and a SWS E1 on my bull barreled 260. First I've got to decide on the final profile/length of the 260 barrel. I look forward to having the basic round FF tube sitting in my drawer......but probably not for long. I see a short and lightweight upper in my future. Damn BRD. Grizz |
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I just measured my DPMS upper & got 2.064 ( upper is almost two years old now, so I have the old version )and I have a fulton Armory hand guard on it with the 12" rail . I can put a straight edge between the two rails & can see just a 0.001 or two of day light ,very close .
I will tell you one thing ,I had to reverse the Brownell's rail alignment tool to get it to work on the DPMS upper rail to align the two rails. The DPMS is too tight to get the correct end of the tool on it . Not so with my SI Defence upper (gen.II ),the tool slides right on there . Not complaining , The DPMS build is a fine shooter. Sniperx I'm also interested in the RS2 hand guard for the SI Defence upper I am building . I see that the photo has DPMS on the hand guard , but the is listed for the AR 10 ( and you know how all them people get bent out of shape if some one mentions it in the same breath as a DPMS ) . Is it available in the DPMS format also ? Now I have to measure my SI Defence upper to see what the rail height is & the answer is ,2.064 , just like my older DPMS upper . How will that work with your rail ? I plan on using iron sights with this build almost exclusively ,so the rail heights must be close. Thanks . Just when ya think you have a handle on building one of these 308's , ya get a new curve . |
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DPMS owners of new rifles please take note that no other rail system will mate with your new upper. All of the below are at the same elevation.
RRA at same elevation from centerline of barrel. SR25 same elevation AR10 same elevation old Bushmasters same elevation, guess you only have one choice DPMS
ETA: for now |
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On the left is the a3 dpms from midway, on the right is the fulton armory. http://i47.tinypic.com/w8u9og.jpg Below is the finished product, well almost..... 
http://i47.tinypic.com/vgstp2.jpg Looks like they took some of the beef from the top of the rail, weakened it , if ya ask me . |
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This might be helpful when you make a decision about what upper to get.
http://www.midwayusa.com/viewproduct/?productnumber=784553 DPMS Upper Receiver LR-308 A3 Flattop MatteProduct #: 784553| Manufacturer #: 308-FTT-EA1 Customer review. Kendal Baerg of Brookings, SDDate posted: 11/24/2007Purchased for my LR-308 to upgrade so I could get the dust cover, forward assist and shell deflector. Installation was easy with proper tools and works great, the rails are a little bit lower that the standard but I did not have any problems with mounting my shepherd scope as far as clearance from the barrel guard. 308-FTT-EA1/ 308-FTT-EA is what you want to stay away from if you want to make sure that your non-DPMS quad rail system lines up. http://www.dpmsinc.com/store/products/?prod=1702&cat=1705 Low style flattop allows use of Detachable Carry Handle "I hope that they understand that Carry Handles are not as popular as they once were. These rifles are mostly being used with Powered Scopes. If not scopes, then, Aimpoint, Eotech, Trijicon ect. Which are not compatible with carry handles. That is what slings are for." Model: 308-UR-36 might be the DPMS receiver to get. This rail from DPMS was designed for the Low Pro 308-FTT-EA1 http://media.midwayusa.com/ProductImages/Medium/295049.jpg This free-float handguard features a vented free-float tube and 4 Picatinny-style rails for mounting accessories. The handguard is available in two heights, low and high. The low handguard is designed for the A3-style upper while the high handguard is designed for the original LR-308 upper. I wish that they would have disclosed this more out in the open. We all try our best to make sure that we get the right parts and sometimes 30 days pass before when can afford to get a new part and then find out that something is not right with the one purchased more that a month ago. Its a set back but we can bounce back from it. |
| Don't let DPMS pull the wool over your eyes... DPMS changed the rail height last year, I spoke to one of their techs! Basically its a shit move to be totally proprietary. In that only our rails fit our guns. As a result, no aftermarket rails will REALLY mate up correctly... Thanks DPMS, I'll never buy another thing from you! |
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Sandsleep, thank you for sharing your problem. I want to use the E1 rail also, could you show a close up pic of your new setup. Thanks
Thanks to Vanderhemi, I just got a Fulton upper receiver. They still have the correct old receiver, now I can continue with my build
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Fulton Armory+ SWS E1 rail= perfect alingment
Im glad fulton armory didn't change their specs. It was a crap move imo that dpms changed the specs just so that we have to buy their rails for their new receivers. Most dpms rails are backordered several months. Art from SWS makes awesome rails no matter which one you get. Maybe Art should start machining out some receivers also 
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We started some uppers some time ago, but they were AR15 for the time being.
I have sent a lot of people to Fulton including some very large volume orders. One of them is going to make thier own uppers. My buddy at Jet Supressors makes uppers and lowers. Some of his work is pictured on the front page of my website 
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I too asked DPMS why the change. Their response was, "To make it compatible with our other LR308 parts". In other words, buy DPMS (YHM) rails. This is disappointing. I was going to build a duplicate of my modified LR308-AP4 shown below. Since the DD Lite Rail will be .060" taller than the receiver rail, I'm going to look elsewhere. I wonder what Fulton Armory is going to do when their current DPMS receiver stock runs out???
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GA Precision told me that they stopped making LR308 uppers due to DPMS changing the rail specs.
They would do work on a Fulton upper but they weren't taking any new orders when I corresponded with them in Feb. So I just went with a Titan M110 upper for the time being. I may try a GA Precision upper later. |
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I just bought one of their Titan M110 uppers with a Daniel Defense Lite rail (during President's Day Sale). The upper rail from the Fulton is the same height as the DD rail. But yes, their stuff is DPMS I believe. The real question is, as Fulton's current stock of uppers is sold and they get a new batch from DPMS, will they keep the current specs or not? |
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I just bought one of their Titan M110 uppers with a Daniel Defense Lite rail (during President's Day Sale). The upper rail from the Fulton is the same height as the DD rail. But yes, their stuff is DPMS I believe. The real question is, as Fulton's current stock of uppers is sold and they get a new batch from DPMS, will they keep the current specs or not? Exactly! I'm guessing Fulton bought up as many of the old, taller uppers as they could. They are probably trying to find another source now. |
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I just bought one of their Titan M110 uppers with a Daniel Defense Lite rail (during President's Day Sale). The upper rail from the Fulton is the same height as the DD rail. But yes, their stuff is DPMS I believe. The real question is, as Fulton's current stock of uppers is sold and they get a new batch from DPMS, will they keep the current specs or not? I posted this on Snipershide and thought it would be helpful here. Fulton will continue to have their receivers produced at their custom specs. DPMS stated "that other manufacturers (DPMS already has) that make rail systems specifically for the LR308 line are in the process of updating their products to match." I was doubtful of the statement because that would mean the manufacturers would only be compatible with DPMS or have to create a new product line just for DPMS. I called Daniel Defense and they specifically told me they will not be updating their rails to DPMS's new height. Fulton Armory said their custom specifications for upper receiver rails will not be changing. I expect similar comments from other manufacturers. To date, I do not know of any manufacturer that has changed its design or created a new design to work with DPMS. |
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Our AR15 receivers are all the same height except the High Rider and Tri-Mount. I wonder if that's what Mark was thinking of in his reply. The LR308 Platform has two heights, the A3 and Lo-Pro Raised Rail. The A3 was changed recently to better accommodate our other components. I guess in reality, with the number sold before the change, there are now 3 heights. To find out if you have a newer model or older run, the easiest way to measure is with a caliper from the bottom surface that mates to the lower to the top of the rail. The new versions measure 2.003 and the old versions are 2.063. Any larger receiver rail to handguard rail height difference would be due to the lack of an industry standard in the large frame AR style rifles. Everybody is still pretty much making their own thing and some measurements just don't line up between manufacturers. Just remove the pins & separate the upper to measure. |
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