rmart Posted February 12, 2014 Report Share Posted February 12, 2014 I have a brand new upper for my DPMS 308 AR. (yay me) It's a DPMS upper receiver (low profile) with a DEZ national match 18" barrel, ICE Arms BCG, JP Enterprises modular handguard, and Troy muzzle brake. All in all it's a very nice package but I find a problem... The handguard by JP Enterprises allows for the addition of a rail on top for sights and accessories. I purchased said rail and attempted to install it on the handguard only to find that it sits about 1/16" higher than the rail on the upper receiver. What is wrong with DPMS that they make their uppers with a proprietary dimension, and what's up with JP Enterprises that after what, five years? they don't make a compatible rail and handguard for the DPMS uppers? Whether or not DPMS is the best .308 AR out there, they're certainly the most common and one would think they'd have an option to fit the DPMS uppers. Grrr... Well, rant over; what can I do to fix this problem other than spend $500 on a different upper receiver and installation, or tossing my now $400 handguard setup and putting something else on? I looked at possibly sanding that approximately 1/16" of an inch off the bottom of the rail but the underside is curved to match the handguard, and the mounting slots would disappear if I did so. Am I really up the creek here? R Quote Link to comment Share on other sites More sharing options...
shibiwan Posted February 12, 2014 Report Share Posted February 12, 2014 You found out the hard way that there are two DPMS 308 upper profiles. The newer low profile uppers were designed so that the rail height would be the same as an AR15, which makes more aftermarket bits exchange a little easier. Every other manufacturer making 308 uppers have stuck to the "high profile" design. Honestly, I think they messed it up... to make matters worse there's the new DPMS GII pattern (this makes it pattern #3) to add to the confusion. Quote Link to comment Share on other sites More sharing options...
rmart Posted February 13, 2014 Author Report Share Posted February 13, 2014 So, do I need the older DPMS upper? Are those still available? Quote Link to comment Share on other sites More sharing options...
george_995 Posted February 13, 2014 Report Share Posted February 13, 2014 I have the same handguard(15") and rail, but mega maten receivers. The add on rail sits lower than the receiver rail, talk about pissed off. I've thought about calling JP to see if they would/ could swapp the rail for something correct. I paid 89$ for this rail from Rainiers. Quote Link to comment Share on other sites More sharing options...
rmart Posted February 13, 2014 Author Report Share Posted February 13, 2014 I paid $99 plus shipping for the rail, also from Rainier Arms. I hope they'll take it back. Quote Link to comment Share on other sites More sharing options...
shibiwan Posted February 13, 2014 Report Share Posted February 13, 2014 So, do I need the older DPMS upper? Are those still available? Almost any non-DPMS-made 308 upper is still the high profile (this includes the Remington R25 and Bushmaster offerings) . Not sure if DPMS still makes them with the old "high profile" since the switch in 2009 The only rails I know that is "DPMS low-profile" 308 compatible are from Troy, Apex and Samson. I bet there are a couple more out there but I don't recall who else. Quote Link to comment Share on other sites More sharing options...
rmart Posted February 13, 2014 Author Report Share Posted February 13, 2014 I thought the R25 WAS the DPMS. My understanding was that Freedom Group owned both DPMS and Remington and used the DPMS LR series rifles to make the R25. Am I incorrect in my understanding? Quote Link to comment Share on other sites More sharing options...
shibiwan Posted February 13, 2014 Report Share Posted February 13, 2014 I thought the R25 WAS the DPMS. My understanding was that Freedom Group owned both DPMS and Remington and used the DPMS LR series rifles to make the R25. Am I incorrect in my understanding? You're correct. That's was the point I was trying to put across. Probably could have done it better. :D Quote Link to comment Share on other sites More sharing options...
rmart Posted February 13, 2014 Author Report Share Posted February 13, 2014 OK, so a R25 and/or Bushmaster would be the same low profile upper as the DPMS. At this point my only option is to return the rail to Rainier and try to prevail upon JP to come up with a DPMS compatible rail. (lol, good luck with that, eh?) I guess my rifle is going to have to be optics only which I hate. Quote Link to comment Share on other sites More sharing options...
shibiwan Posted February 13, 2014 Report Share Posted February 13, 2014 OK, so a R25 and/or Bushmaster would be the same low profile upper as the DPMS. At this point my only option is to return the rail to Rainier and try to prevail upon JP to come up with a DPMS compatible rail. (lol, good luck with that, eh?) I guess my rifle is going to have to be optics only which I hate. If you're worried about someone jumping you when you're busy engaging long distance targets, you could piggyback mount an RDS off the scope tube..... Quote Link to comment Share on other sites More sharing options...
rmart Posted February 13, 2014 Author Report Share Posted February 13, 2014 Oh, I don't expect to be getting into any combat situations... I'm just too old and slow for all that. I just like having a rifle sight option for all my rifles in the event that something goes wrong with the optic sights. I hate having limited options right off the bat. Quote Link to comment Share on other sites More sharing options...
rmart Posted February 13, 2014 Author Report Share Posted February 13, 2014 (edited) All right, here's an option... I was speaking with Dave at JP and he suggested something interesting. I don't know where to find one, nor do I even know what you would call it but, an option to address my problem might be this: I'm envisioning something like a gas block with a rail on top, maybe 1 to 1.5" long. This would clamp over the barrel just forward of the handguard and just behind the flash hider. Not a gas block as I have one already, tucked inside the handguard but something like it. I wonder if a gas block could be employed in this manner... The barrel O.D. mics out at around .740 which would be around the fluted area. Just forward of the fluted area and just behind the flash hider is a slightly smaller area approximately 5/8" long. Does anyone have any ideas that might fill this need? Thanks, R Edit: I'm thinking adding a gas block forward of the handguard might be my only real option. I'll then have to get a gas block height front sight. I'm partial to Midwest Industries sights. Anyone have a suggested part number for the appropriate gas block for the low profile upper? Edited February 13, 2014 by rmart Quote Link to comment Share on other sites More sharing options...
shibiwan Posted February 14, 2014 Report Share Posted February 14, 2014 How about a railed gas block like this? If you're using the lo-pro DPMS receiver, any AR15-spec railed gas block should work. Sounds like your barrel has a 0.75" gas block journal. I have this on the beater: Or you something like this: Strongly recommend the steel or stainless steel setscrew styles, avoid the clamped on ones. Quote Link to comment Share on other sites More sharing options...
george_995 Posted February 15, 2014 Report Share Posted February 15, 2014 Do you have the 15.5" long jp handguard? If you do, maybe we could swap rails to see if each others rail works with the different platforms. LMK, Thank you. Quote Link to comment Share on other sites More sharing options...
blue109 Posted February 15, 2014 Report Share Posted February 15, 2014 ^ I was thinking that. Maybe you guys should measure how tall the rail section is? Does JP make rails for different platforms? Quote Link to comment Share on other sites More sharing options...
survivalshop Posted February 15, 2014 Report Share Posted February 15, 2014 I thought they used to make two different add on rail heights , 3/8" & 1/4" ? Do not see it on there sight any more , probably why he recommended the railed gas block. There rails , I believe are proprietary, I haven't found one yet that will fit there hole pattern , with out alteration. Quote Link to comment Share on other sites More sharing options...
rmart Posted February 15, 2014 Author Report Share Posted February 15, 2014 Do you have the 15.5" long jp handguard? If you do, maybe we could swap rails to see if each others rail works with the different platforms. LMK, Thank you. According to JP, and from what I can see they're right, the top of the tube is so close to the gas tube that it can't be made any more low profile. To do so would require a channel to be cut out of the top of the handguard for the rail to be brazed into, and a groove to be cut into the bottom of the rail to allow clearance between the bottom of the rail and the gas tube. They have no plans at this time to make a DPMS compatible system. Dave's argument is that they've only had this issue come up twice with customers so they feel the market isn't demanding the option. My argument that with DPMS, Remington, and Bushmaster all using the DPMS low profile upper the market has to be there as my completely undeducated guess is that DPMS probably supplies uppers to more than half the .308 AR market already. The rail in question is probably about as low profile as it can get as well. I looked at the possibility of reducing its profile on the bottom end but to do so would remove the shoulders of the screw slots making it impossible for the screws to hold the rail down. DPMS of course wants to sell me a different rail system... Quote Link to comment Share on other sites More sharing options...
rmart Posted February 16, 2014 Author Report Share Posted February 16, 2014 How is the set screw gas block secured, and would there be any problems with attaching it to the fluted portion of a fluted barrel? How about a railed gas block like this? If you're using the lo-pro DPMS receiver, any AR15-spec railed gas block should work. Sounds like your barrel has a 0.75" gas block journal. I have this on the beater: Or you something like this: Strongly recommend the steel or stainless steel setscrew styles, avoid the clamped on ones. Quote Link to comment Share on other sites More sharing options...
survivalshop Posted February 16, 2014 Report Share Posted February 16, 2014 The barrel, forward or towards the Muzzle will be of smaller diameter of the gas block turned area of the Barrel . It may secure enough for sight operation , but also may too loose for attachment . How about a railed gas block like this? If you're using the lo-pro DPMS receiver, any AR15-spec railed gas block should work. Sounds like your barrel has a 0.75" gas block journal. I have this on the beater: Or you something like this: Strongly recommend the steel or stainless steel setscrew styles, avoid the clamped on ones. What's wrong with a clamp on gas block ? This is what you are talking about I just switched out a Tactical Machining 308 Upper Receiver from a SI Defense Billet Upper receiver & I thought they made the old rail height , oh well . The JP AR 15 hand guard is the same Diameter as the 308 ( 2.20" ), The Barrel nut has to be different . This is the same JP hand guard , be it newer than the one on the 308 ,but it matches up perfectly on my POF . Quote Link to comment Share on other sites More sharing options...
rmart Posted February 18, 2014 Author Report Share Posted February 18, 2014 OK, my OCD is preventing me from doing anything other than doing this right... That means I need to replace my upper. The upper in your lower picture is a POF upper? It's compatible with a DPMS lower receiver? It appears that the rail lines up perfectly. Do you know if the BCM Gunfighter charging handle is compatible with the POF upper? Finally, is the POF upper a high quality piece, and where is the best place to obtain one? Thanks, R Quote Link to comment Share on other sites More sharing options...
blue109 Posted February 18, 2014 Report Share Posted February 18, 2014 I think Fulton still uses the old height? Might be worth a phone call. Made by DPMS so there won't be compatibility issues. Quote Link to comment Share on other sites More sharing options...
rmart Posted February 18, 2014 Author Report Share Posted February 18, 2014 Not seeing a stripped upper on their website. I'll have to give them a call. Quote Link to comment Share on other sites More sharing options...
rmart Posted February 19, 2014 Author Report Share Posted February 19, 2014 Was just advised by POF that their uppers are not compatible with DPMS lowers. Any suggestions on a 100% compatible 308 upper that would have the correct rail height? Quote Link to comment Share on other sites More sharing options...
98Z5V Posted February 19, 2014 Report Share Posted February 19, 2014 Any suggestions on a 100% compatible 308 upper that would have the correct rail height? Yeah, the upper that matches your lower. No kidding. More often than not, you see issues on the .308 AR platform when you're trying to mix-n-match parts. THAT is when you run into problems with "my gun doesn't run" questions. Get the upper receiver that your lower receiver manufacturer makes. Seriously. Quote Link to comment Share on other sites More sharing options...
rmart Posted February 19, 2014 Author Report Share Posted February 19, 2014 All right, I can accept that. What I need then is the DPMS A3 upper that has the slightly higher rail height. I've looked all over for a part number to search for. DPMS claims they only offer the low-profile upper or the slick-side upper. I'm looking for the part number for the pre-2009 A3 upper. Any idea where I can locate that part or number? DPMS is less than helpful. Quote Link to comment Share on other sites More sharing options...
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