archangel2003

Yeah, I snatched them out of the wife’s purse and she never noticed them gone!

It's still not as hard to remove off the Delta Ring as the same setup on the AR-15, but not nearly as easy as it used to be. I'm tempted to trim the back end under the AR-15 Delta Ring to make removal more reasonable.

OK, I took the advise and pulled out the razor knife, files and used the belt grinder. First 2 pictures. I took the all the internal parts off the back end where the hand guards locate under the Delta Ring. Next 2 pictures. I then ground the front inner tabs level with the outer tabs, then took down the triangle end cap to match and the second is it installed. Next Picture. All that was not enough so the part that the delta ring grabs that were too long were shortened. Next 2 Pictures. The retaining tabs for the delta ring were still in the way so off they came. Yeah, with the hand guards off the delta ring and spring will be loose but not something I'm worried about. After all that, they now fit, just don't look too close when they are apart. The last picture is it installed at the Delta Ring.

If I were to mark the gas tube as it's mounted, then take the gas block off and push the tube in further, how much free play/clearance should it take up before touching the bolt gas tube receiver? Also, to measure the gas port location on the barrel, what is the reference point we measure from? In my case, the gas port would need be to be further away from the chamber making the gas tube possibly hit if it were too close.

Every source I found says that the gas tubes for the AR-15 and the AR-10 are the same length no matter the gun length/size.

OK, I found a post listing various barrel nut threads.

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.

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

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"

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.

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.

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.

Yep, it looked to be somewhere in the 1/4 area. The question is why? I looked at the local gun stores and non had a DPMS 308 barrel nut, or any barrel nus of any kind. They had stripped lowers and the parts for them, stripped uppers, and all kind of other parts, but no barrel nuts.

Yeah, it's a cross section of the barrel nut with the .733 measurement being the inner threads. I refer to the left side as the front. The .121 measurement width is the serrations that the hand guard mounts to and if it were so that the front of the .121 measurement were at the back of the .125 measurement (.250 back from the face) it would align for the hand guard.

Here are my measurements.

Thank you. I await your dimensions.

I already have 2 sets of (thankfully cheap) hand guards that are too long. I wish I knew someone near me who builds AR's

I did notice the AR-15 is near impossible to get the delta ring back far enough by hand to get the guards off, and the AR-308 is real easy as they are not as deep in the delta ring.

I don't have an ARA-15 barrel nut available without tearing down a rifle. I have been looking on line and the DPMS-308 look just like mine with the serrations at the front, and with the delta ring installed, the serrations seem to be closer to the front like mine look. Just to make sure I'm not pulling a bonehead, but, the slip in hand guards ARE the same lengths (Carbine, Mid length, and Rifle length) for the AR-15 and the AR-308. When looking for them, they all indicated they were the same lengths, so mid length AR-15 grips and gas system was the same as a mid length AR-308. The mid length gas system on both of my rifles used the same gas tube and gas block (the AR-15 and the AR-308).

Well, I have 1.060 for the total length of the barrel nut, front to back, and the threads are .739 deep from the back to the barrel nut contact face. So the front of the barrel nut forward of the contact face is .321 from where the nut touches the barrel (nut contact face). The width of the serrations is .1180 so subtract 1/2 of that leaves the serrations centered at .262 in front of where the nut touches the barrel. Those serrations are where the groove that the hand guards locate on. If anyone had a DPMS 308 barrel nut and can take measurements we can verify if it is correct. I have to assume the gas block locating shoulder, and barrel mounting face are properly located as the gas tube is located where it should be in the upper. My bet is the serrations on the DPMS nut are further back from the end of the nut. If the serrations were even with the contact face, my hand guards would fit.

Everything lengthwise seems to be correct except the barrel nut. It looks like the barrel nut serrations where the wrench grabs it, are spaced further forward, and that seems to be the reason the delta ring is so easy to get past. The barrel nut is from Palmetto State Armory so I'm going to take it off and measure it. Comparing those measurements to a known DPMS barrel nut should verify if that is the issue or not.

Yep, looks like yours only cleaner as it has zero rounds through it.

The had guards are supposed to fit both as long as they are mid length gas system. If you look at the pictures, the close up of the gas block, you will see that when the bottom is installed properly the hand guard is too long. If I had access to the proper dimensions of the mid length gas system barrel, I could verify where the mismatch is. I guess I'll be looking for the least expensive free float system I can find.

Here are some pictures. The had guards are from CDNN https://www.cdnnsports.com/handguard-midlength-single.html AR15 HANDGUARD MIDLENGTH SINGLE INSULATED ORIGINAL EQUIPMENT Manufacturer: ORIGINAL EQUIPMENT Model: AR15/M16 Color: BLACK Composition: SYNTHETIC SKU: DANML UPC: 783583556071 I have the same set on my AR-15 that is also a mid length barrel gas system and it fits. On the AR-15 the bottom is a PITA to get past the delta ring, but much easier to get past the delta ring on the 308 as the nut serrations are higher up, but if I put the top in first, the bottom would not even pass the Delta ring.

I got the Mid length gas system but the mid length had guards do not fit. On my 16 inch AR-15 with a mid length gas system barrel, the had guard is just long enough so that the front had guard cover and gas block fits flush with the barrel step at the gas port. On my 18 inch AR-308 with a mid length gas system barrel, the hand guards are about 1/4 inch too long so the front cover is too far forward, and the gas block is is too far forward and the gas port does not line up. I though mid length was mid length no matter if it was AR-15 or AR-308. Everything on the AR-15 upper fits like it should. The barrel is a LOSOK Black Nitride 7.62 NATO (.308/7.62x51) 18 in. It's mounted on a DPMS 308 A3 upper receiver. It is held by a PSA PA10 .308 barrel nut and delta ring assembly. Any Ideas? I don't have the dimensions of the mid length barrel or gas system so am not sure what is off.