hondo

Thanks guys, wide open it will be! Thanks 98Z5V, great new build first fire tips! With the virus "shelter in home", "no travel unless essential", it will be a while before I go to a range.

I have an Odin adjustable clamp-on gas block on my new build. After researching on the net I've found two primary schools of thought on initial set-up of the gas block. One school of thought is wide open for the first shot then adjust for less gas flow, blah blah blah. Another is to shut off the gas flow turning your weapon into a single shot then open the gas block until proper function in obtained. I tend to favor the second version, what say you? I bought an adjustable gas block because with a 16 barrel with mid gas system I felt my build might be over gassed.

I found a YouTube video where someone was disassembling his DPMS .308 and lubing it and when he got to the bolt carrier it looked identical to mine including the retaining pin but the gas ring was not a one piece gas ring. The 3 ring gaps were clearly visible. The local dealer, The Outdoorsman Sports Shop, sells a lot of stuff they buy repackaged into bags they label with what it is and how much it costs, not what brand it is. When I asked recently (purchased over a year ago) they said they would know where what they selling came from when it was purchased but too much time had passed. They sell a lot of quality stuff so I'm not worried that it's junk, after all it has the one piece gas ring. I've purchased several Aero-Precision matched uppers/lowers from them as well as a POF lower and many small parts such including one each DPMS .223/.308 lower parts kits as well as a DPMS .308 A2 stock kit. I've seen several brands of .308 bolt carriers that look exactly like a DPMS carrier's bolt end i.e. multiple flat surfaces such a Luth and APF.

Sorry, I need to be schooled on how to post pictures. It looks exactly like the bolt carrier in the link above, even to the gas key being staked from the side and no forward assist serrations. The pin holding the firing pin has a countersunk flat head, not a loop like a cotter pin. The bolt has a one piece gas ring. No identifying engraving on the carrier. I'm just curious enough to want to know the metal makeup of the carrier and bolt. I was hoping that the countersunk flat head firing pin retaining pin and one piece McFarland/JP/? gas ring would be a clue to a quality piece, or not. Of course due to the time frame from when I purchased the bolt carrier assembly and I questioned my local gun shop crew they didn't know what they had ordered.

I bought a .308 bolt carrier assembly from a local dealer quite some time ago as I was stockpiling parts for this build. The bolt carrier has no id marks but looks like a DPMS as shown on Midway USA site. https://www.midwayusa.com/product/1413131451 The bolt retaining pin looks like a split nail with a flat head and the bolt has a one piece ring like a McFarland ring. What do I have???

I installed a Miculek muzzle brake today so I could remove the upper from the vise it was occupying. Just lightly tilting the upper, muzzle down, allowed an assessment of the bolt carrier gas key to gas tube fit. Perfect, one finger into the ejection port sliding the bolt carrier back and forth, I was unable to feel any hesitation or snag as the gas key passed over the gas tube. I guess I had an underlying fear that I had an out of spec upper.

Due to my inability to buy extra barrel nuts for the two handguards I have I didn't want to risk messing one up modifying it so I ended up buying another free float handguard that uses a barrel nut that the gas tube goes over, not through the barrel nut. Unfortunately, the company, AP Custom is out of business. A very nice, carbon fiber 9" octagonal tube. Barrel nut is torqued to 60ft.lbs., gas tube fits fine and extends to the middle of the bolt pin cutout, all is well.

Yes, the barrel nut "port" that aligns with the uppers "cloverleaf" is too high vertically when torqued, i.e. the 12 o'clock position. I need a brand name forearm for a DPMS Low upper that has a DPMS gas port 0.845" radius/1.690" bolt circle diameter barrel nut rather than the two previously mentioned that thread-on and torque fine but are Armalite gas port 0.860" radius bolt circle diameter. In other words a smaller radius/bolt circle diameter would lower the barrel nut gas port holes. I'm thinking about drilling out the offending port 1/32" larger which will lower the bottom of the "port" but only if I can get a spare barrel nut. I've e-mailed both Mentium USA and EGW to see if they would sell their barrel nuts by itself because if I scrap the one that came with the forearm(s) then I've gained nothing. I found a thread on this forum that referenced a gas tube "rubbing/laying on" a barrel nut without adequate clearance to enter an upper but the thread died. I've found a few threads where the gas tube required tweaking but that's not my problem.

It opens for me but here is a link, https://yhm.net/accessories/forearms/handguard-accessories.html scroll down to part YHM-9483. I know this part is for an AR-15 but that is what the Mentium USA barrel nut looks like. I believe the problem is that although both the Mentium USA and EGW barrel nuts are DPMS 1 7/16"x16tpi, the gas tube radius holes are Armalite radius of 0.860", 0.869" in the case of the EGW instead of DPMS radius of 0.845". In the case of the EGW free float tube it was inexpensive but exactly what I wanted, a plain tube. The Mentium USA was on sale, stated to fit a DPMS Low upper and the rib matches well but without the gas tube installed due to the barrel nuts Armalite gas tube hole radius.

Yes, the longer radius EGW barrel nut made the mismatch worse. An 0.845" radius barrel nut would probably be ideal. I'm thinking about ordering a spare barrel nut and drilling out the offending hole.

I've found references to at least three DPMS pattern barrel nut variations, 0.86" radius/1.720" bolt circle diameter, 0.845" radius/1.690" bolt circle diameter, and EGW 0.869" radius/1.738" bolt circle diameter. Just for fun I torqued up an EGW barrel nut and the interference was worse at the 12 o'clock position. I could of course use a barrel nut such as a JBL where the gas tube goes over the barrel nut rather than through the barrel nut but I'd like to use one of the free float tubes I have on hand. Interesting that both of the above mentioned barrel nuts ended up at 90ft.lbs of torque to line up. I'm going to temporarily mount the gas block with tube to check if the uppers gas tube "cloverleaf" is in spec.

When I typed, "The barrel nut looks like a DPMS barrel nut with 22 holes." I should have typed a DPMS pattern barrel nut with 22 holes. It looks like this only with 22 holes. 748354.wdp.jxr

DPMS .308 low build. The Mentium USA free float handguard barrel nut fits and is aligned but the gas tube can't be inserted. Imagine a clock face, 12-3-6-9, at the 12 position, under the flat top, the gas tube hole alignment rib is blocking insertion of a pin/gas tube. At the 3-6-9 position a smaller tube inserts and doesn't snag when inserted. So I placed a weapon light into the upper and it appears to be at least 0.060" of an obstruction. Once again, ALL of the alignment issue is at that one rib of the uppers gas tube hole, vertical position when holding the firearm. The barrel nut looks like a DPMS barrel nut with 22 holes. A PRI DPMS/KAC barrel nut wrench fits the barrel nut and was used to torque the barrel nut.