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Posted: 12/7/2025 12:15:19 AM EDT
Looking to close in all the holes through a barrel nut to contain gas and pressure in a blowback pistol cal integral. I guess im leaning towards getting the perfect size aluminum rod and freeze/pressing in to each hole. Or using JB weld and just filling them. I’d like to stay away from real welding or spending the $$ on a custom barrel nut. Anyone have any tips? 
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Originally Posted By chevrofreak: This. You could alternate the side of the nut from front to back so that holes next to each other are not tapped on the same side, which should help prevent cracking. Originally Posted By chevrofreak: Originally Posted By sparky923: Tap Set screws This. You could alternate the side of the nut from front to back so that holes next to each other are not tapped on the same side, which should help prevent cracking. I like that idea. The holes measure around ~ 5.2mm to 5.5mm so I’d probably go with common M6x1.0. I just need to make sure there’s an even number of holes to properly alternate front and back (looks like 20 so 10 front 10 back), and that the pin wrench won’t hit any of the set screws on the front side Screw it, I just went ahead and ordered 2x 10 packs of stainless m6 grub screws for $15 total. That’s not much more expensive than the JB weld or RTV options |
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I like the aluminum rod idea. They can be cooled, and the nut can be heated to get a firm fit as you press them in. If it's a slip fit....you can use a high-temp loctite to help keep them in place. Plus....threading a bunch of holes and then having to locktite a bunch of set screws....seems like more work, and a little extra weight. . |
Occid Vel Occisus Est !!
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Originally Posted By IdahoPCCinc: I like the aluminum rod idea. They can be cooled, and the nut can be heated to get a firm fit as you press them in. If it's a slip fit....you can use a high-temp loctite to help keep them in place. Plus....threading a bunch of holes and then having to locktite a bunch of set screws....seems like more work, and a little extra weight. . It would be easier but I’d prettymuch have to order 5mm or 5.5mm rod and then be at the mercy of the variation in hole diameter to determine if it’s a slip/press/interference fit |
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Originally Posted By KELBEAST: Looking to close in all the holes through a barrel nut to contain gas and pressure in a blowback pistol cal integral. I guess im leaning towards getting the perfect size aluminum rod and freeze/pressing in to each hole. Or using JB weld and just filling them. I'd like to stay away from real welding or spending the $$ on a custom barrel nut. Anyone have any tips? https://i.ibb.co/Nnd6LLzN/IMG-4318.webp Trying to rap my head around why you think this is beneficial? Any gas pressure released in a blowback will be inside the upper receiver. Are you trying to prevent any gas from going forward into the handguard? Lap the front of the receiver to get a good fit between the barrel extension/receiver and loktite the barrel extension into the receiver to seal it up completely. |
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Originally Posted By Blowout: Trying to rap my head around why you think this is beneficial? Any gas pressure released in a blowback will be inside the upper receiver. Are you trying to prevent any gas from going forward into the handguard? Lap the front of the receiver to get a good fit between the barrel extension/receiver and loktite the barrel extension into the receiver to seal it up completely. |
"Major, with the weapon shops out of the way we can introduce steadying laws that could not be flouted." -A.E. Van Vogt 1951
Easy and ghetto? Tin snip a soup can lid and JB Weld it over everything but the correctly indexed hole.  Originally Posted By MaxSpeed74: Originally Posted By Blowout: Trying to rap my head around why you think this is beneficial? Any gas pressure released in a blowback will be inside the upper receiver. Are you trying to prevent any gas from going forward into the handguard? Lap the front of the receiver to get a good fit between the barrel extension/receiver and loktite the barrel extension into the receiver to seal it up completely. He says integral, that likely means he's wanting to turn the tube handguard into a suppressor body with a ton of internal volume. |
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Originally Posted By Blowout: Trying to rap my head around why you think this is beneficial? Any gas pressure released in a blowback will be inside the upper receiver. Are you trying to prevent any gas from going forward into the handguard? Lap the front of the receiver to get a good fit between the barrel extension/receiver and loktite the barrel extension into the receiver to seal it up completely. This is not going on a blowback. Hell, it’s not even going on an AR. It’s going on a bolt action rifle and I’m going to be drilling holes in the barrel like an mp5sd and then creating a chamber in the rear of the integral 
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Originally Posted By KELBEAST: It would be easier but I’d prettymuch have to order 5mm or 5.5mm rod and then be at the mercy of the variation in hole diameter to determine if it’s a slip/press/interference fit Originally Posted By KELBEAST: Originally Posted By IdahoPCCinc: I like the aluminum rod idea. They can be cooled, and the nut can be heated to get a firm fit as you press them in. If it's a slip fit....you can use a high-temp loctite to help keep them in place. Plus....threading a bunch of holes and then having to locktite a bunch of set screws....seems like more work, and a little extra weight. . It would be easier but I’d prettymuch have to order 5mm or 5.5mm rod and then be at the mercy of the variation in hole diameter to determine if it’s a slip/press/interference fit OP.....get a pair of calipers, and then measure each hole to see the actual dimension, and variances from hole to hole. Please share the dimension of the hole in decimal inch. ( like .123 ) Then, if the variance is less than .005-.010 (inches not mm) get a reamer that is close to a nominal rod size. Example.....let's say the hole is averaging .244-.246 inches Order a .2495 reamer, and order .250 aluminum rod stock. Then just ream all holes to .2495 Then you cut the rod to length, deburr the ends, toss the pieces in the freezer. Toss the nut in the oven at 150-160 degrees. Pull everything out and carefully try tapping a few rods into the holes. They should go in with a little tapping. If you do get a loose one, you can use a punch on the end of the rod edge to push the material up on the end of the hole. It's like staking the hardware on a BCG This should lock it in place pretty good. |
Occid Vel Occisus Est !!
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Originally Posted By KELBEAST: This is not going on a blowback. Hell, it's not even going on an AR. It's going on a bolt action rifle and I'm going to be drilling holes in the barrel like an mp5sd and then creating a chamber in the rear of the integral https://i.ibb.co/YTXt29P9/IMG-4378.jpg Why would you post this in the AR15 BIY forum? It should in the silencer BIY forum. |
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Originally Posted By Blowout: Details like these are priceless when asking for suggestions... Why would you post this in the AR15 BIY forum? It should in the silencer BIY forum. Because the part in question is an AR15 part. The BIY silencer forum gets way less traffic than the AR build forum. And I got the suggestion I was looking for and it’s happening. 
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Originally Posted By TonyRumore: When the hand guard tube pressurizes up, you don’t want those rods/pins to be blown out, fly out the back of the nut, and shoot yourself with them. Just a word of caution. Tony You do realize it would take A LOT of pressure to blow out a press fit pin that's been peened/loctited.... like way more than a suppressor could generate. More especially since a suppressor vents out the barrel when pressure is created. OP....I'm glad you decided on a course of action and are moving forward on this. Personally, I would hunt down some aluminum set screws to save some weight. I'm genuinely interested in seeing you complete this, and maybe doing something similar myself with 9mm. . |
Occid Vel Occisus Est !!
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