survivalshop Posted April 21, 2016 Report Share Posted April 21, 2016 (edited) Not sure how your Barrel nut looks like , but here is the AR 15 Barrel Nut. Your asking why are the Barrel Nuts different , the 308AR has to be larger because of the larger 308 Barrel"s Chamber area , its larger dia. & length , of course & your trying to fit AR 15, 5.56 Hand Guards to a proportionally different 308AR . I don't think I have heard of anyone installing AR 15 Hand Guards to a 308AR , that didn't need fitment . I know the last set of Mid length I installed on an AR 15 were a bitch to put on & I struggled with them for quite some time to get them on. 12 hours ago, archangel2003 said: Here are my measurements. Your Barrel Nut length of 1.060" , is 0.860" on the AR 15 Barrel Nut . You thread depth of 0.733" , is 0.5255" on the AR 15 Barrel Nut. Can't tell for sure , but are you using the Triangular front cap or the Round one , it may make a difference . Edited April 21, 2016 by survivalshop Quote Link to comment Share on other sites More sharing options...
archangel2003 Posted April 21, 2016 Author Report Share Posted April 21, 2016 (edited) I know the difference between an AR-15 and the larger AR-10 with a larger diameter barrel, larger threads and what not. The gas systems on both my rifles (AR-15 & AR-10) is mid length, and they both use the exact same gas block, the exact same gas tube and they both fit perfectly. I did not want a free float hand guard and was looking for the stock vented hand guard that was not the triangle style. The first one I ordered was the about same diameter, but without the taper it looked a little clunky, then I found these with a slight taper and they look just right. All three fit the AR-15, but are a TOTAL PAIN to remove as the delta ring it so tight, as if the mounting serrations are deeper into the delta ring gap The AR-10 shows the serrations higher up in the delta ring gap and is much easier to remove and install. I just need to have someone who used a mid length gas system and slip in hand guards so I can know what barrel nut works. I'm assuming it's the barrel nut that I'm having issue with. The bottom fits perfectly, and the top fits perfectly, the issue is the hand guard is about .200 to .250 too long so the top and bottom don't fit at the same time. Edited April 21, 2016 by archangel2003 Quote Link to comment Share on other sites More sharing options...
archangel2003 Posted April 21, 2016 Author Report Share Posted April 21, 2016 (edited) If I knew of someplace that sold that hand guard for the AR-308, I would get it, but as far as I can tell, mid length is mid length and not AR-15 or AR-10, it just seem as if they are just the same. Here is the look I was going for. Edited April 21, 2016 by archangel2003 Quote Link to comment Share on other sites More sharing options...
blue109 Posted April 21, 2016 Report Share Posted April 21, 2016 (edited) The gas port length is the same...but the receiver it is bolted to is not. Can't expect the handguard to work on both. Might get lucky though. ETA I don't think I've ever seen a factory built mid 308 with 2 pc handguards. This might be why Edited April 21, 2016 by blue109 Quote Link to comment Share on other sites More sharing options...
archangel2003 Posted April 21, 2016 Author Report Share Posted April 21, 2016 9 hours ago, survivalshop said: Can't tell for sure , but are you using the Triangular front cap or the Round one , it may make a difference . I first ordered the round ones, then, when they did not fit I "found out" (AKA, read the info in them) that these hand guards use the triangle end caps, so now I have both types. The only non-free float hand guards I see are the MagPull ones and they are not pretty. I just wanted the plain ones. The nearest gun manufacturer to me is R-GUNS in Carpentersville, IL, so next time I'm in the area, I'll stop by and bug them in person. One way or another, I'll need to have some type of hand guard and do not want to spend the prices they want for the free float ones. Quote Link to comment Share on other sites More sharing options...
planeflyer21 Posted April 21, 2016 Report Share Posted April 21, 2016 Oh man...both types! Only 42 posts and it's time to start a second build already. <laughing> Quote Link to comment Share on other sites More sharing options...
survivalshop Posted April 21, 2016 Report Share Posted April 21, 2016 (edited) It is not only the Barrel Nut , but as said , the Upper receiver . & how the Barrel Extension fits into it , which may or may not set the Barrel nut away from the Upper more , making the gap or distance to the Gas Block less then an AR 15. If you want to use those HG's on that Rifle , you will need to fit them , as most of us are saying , some do get lucky , probably depending on what manufacturers Upper Receiver your using . Fitment should not be a problem , just by looking at your photo's . Most of the AR Hand guards can be used with the round or triangular front Cap . Have you tried the round one ? Measure the max distance between the AR 15 with Md gas system & Barrel Nut , then your 308AR's system & you will see why they don't fit so easily . I would remove the Barrel Nut & remove the Delta ring assembly & reinstall the Barrel Nut & test fit the Hand Guards with out the Delta Ring in the way & it will give you a better feel of where to remove material & where , on the Hand guard . I would start with the front of the HG in the Front Cap & see what it will take to get the HG to sit over the Barrel Nut properly , you may need to remove material from the front & rear of the Tabs that insert into or over the Barrel Nut & Front end Cap . A Dremel Tool can be your friend & you might be surprised that it will not take as much as you think for them to fit . Also mind the Heat Shields , they can interfere with fitment also . Edited April 21, 2016 by survivalshop Quote Link to comment Share on other sites More sharing options...
survivalshop Posted April 21, 2016 Report Share Posted April 21, 2016 I believe DPMS has built rifles using the A2 Hand Guards , not sure if a Mid Length , but they have used them . Quote Link to comment Share on other sites More sharing options...
archangel2003 Posted April 22, 2016 Author Report Share Posted April 22, 2016 57 minutes ago, survivalshop said: I would start with the front of the HG in the Front Cap & see what it will take to get the HG to sit over the Barrel Nut properly , you may need to remove material from the front & rear of the Tabs that insert into or over the Barrel Nut & Front end Cap . A Dremel Tool can be your friend & you might be surprised that it will not take as much as you think for them to fit . Also mind the Heat Shields , they can interfere with fitment also . The heat shields are no issue, but I would have to remove so much that there would be nothing left on the front to mount to. AND, there are mid length gas system AR-308 uppers that have my style of hand guards. BTW, it's a "DPMS 308 A3 UPPER RECEIVER" Quote Link to comment Share on other sites More sharing options...
survivalshop Posted April 22, 2016 Report Share Posted April 22, 2016 You should take the same amount off each end, not just one end . Check it with the Delta ring assembly removed , you will get a better picture over all , if it can be done & you feel comfortable doing it . Quote Link to comment Share on other sites More sharing options...
blue109 Posted April 22, 2016 Report Share Posted April 22, 2016 I see psa has a middy with standard style handguards. Might be worth trying to email them to see if it's shorter than a standard AR handguard. Quote Link to comment Share on other sites More sharing options...
DNP Posted April 22, 2016 Report Share Posted April 22, 2016 Forgive the crappy penmanship....it ain't pretty normally and it's even harder with a broken hand. My thoughts. Experts, correct me if I'm wrong. Quote Link to comment Share on other sites More sharing options...
planeflyer21 Posted April 22, 2016 Report Share Posted April 22, 2016 7 hours ago, DNP said: Forgive the crappy penmanship....it ain't pretty normally and it's even harder with a broken hand. My thoughts. Experts, correct me if I'm wrong. Looks like a good spatula blueprint to me. Quote Link to comment Share on other sites More sharing options...
DNP Posted April 22, 2016 Report Share Posted April 22, 2016 Hey...I'm doing my best here....they put these in a couple weeks ago and though I was never "right", I ain't as right as I used to be. I think that's a lovely cross section of one half of the handguard. Quote Link to comment Share on other sites More sharing options...
blue109 Posted April 22, 2016 Report Share Posted April 22, 2016 Maybe stick to photos from now on bud? Quote Link to comment Share on other sites More sharing options...
DNP Posted April 22, 2016 Report Share Posted April 22, 2016 man....tough crowd. Alright arch, I tried. If you can't fix it at least you have a start on the worlds next best spatula. Remember me when it makes you rich. Quote Link to comment Share on other sites More sharing options...
archangel2003 Posted April 22, 2016 Author Report Share Posted April 22, 2016 My first few drawings were so bad I tossed them as I did not want it to look like a 5th grader was building an AR-10 Quote Link to comment Share on other sites More sharing options...
shepp Posted April 22, 2016 Report Share Posted April 22, 2016 Cut it down weld it back together problem solved ?? Quote Link to comment Share on other sites More sharing options...
survivalshop Posted April 22, 2016 Report Share Posted April 22, 2016 4 hours ago, DNP said: Hey...I'm doing my best here....they put these in a couple weeks ago and though I was never "right", I ain't as right as I used to be. I think that's a lovely cross section of one half of the handguard. So, you going to the Left now ?? I Quote Link to comment Share on other sites More sharing options...
DNP Posted April 22, 2016 Report Share Posted April 22, 2016 I've always thought it, but now there's proof. I'm screwed. Quote Link to comment Share on other sites More sharing options...
Rsquared Posted April 23, 2016 Report Share Posted April 23, 2016 I just realized that I've been glazing over this thread. My first AR-10 carbine is the A2 style. It came with the A2 handguards as well. I'll have to dig them out and take some measurements. Though, mine being Armalite probably isn't gonna answer the direct question though. Damn Dirk, that looks like you put your hand somewhere that you shouldn't have. Quote Link to comment Share on other sites More sharing options...
archangel2003 Posted April 23, 2016 Author Report Share Posted April 23, 2016 There are so many times throughout my life where I made permanent modifications to something only to find out it was something else and could not put back what was ground off. Rsquared, I would much appreciate some measurements for verification. It might not answer my question directly, but more info is better than not knowing. I would love to have one of each barrel nut, DPMS, AR-10, and any others that might be different so we can verify what is and is not compatible. With my luck, the guy who received the pallet of boxed parts accidentally put an AR-10 barrel nut in the DPMS barrel nut box and the parts picker either did not know the difference, or just did not notice. Quote Link to comment Share on other sites More sharing options...
survivalshop Posted April 24, 2016 Report Share Posted April 24, 2016 AR 10 Barrel Nut has different thread pitch & the two are not inter changeable . Measuring or comparing a DPMS to an AR 10 will not help , AR 10 uses a different length in the gas systems , I believe . The trick to get a proper fitting part is to remove only enough material for proper fitment , a little at a time till it fits . Quote Link to comment Share on other sites More sharing options...
DNP Posted April 24, 2016 Report Share Posted April 24, 2016 So if the gas system between DPMS and AR10 are different....would a HG for one fit different than the other perhaps? Quote Link to comment Share on other sites More sharing options...
blue109 Posted April 24, 2016 Report Share Posted April 24, 2016 Thought only the rifle length was different for AR10? Quote Link to comment Share on other sites More sharing options...
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