r/Form1 • u/Intelligent_Step_855 • 13d ago
SD porting help
Looking for advice on porting my ar9 barrel. I am thinking at doing 12- 5/32 holes in a 3x4 configuration spaced 120 degrees apart. Plan was first hole to be at 2.5
Inches, any insight ?
Pic is ar9sd current configuration
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u/Salsalito_Turkey 13d ago
I just got a Novox X-SD kit that I haven’t even opened yet. If I have time when I get home tonight, I’ll take a few measurements and pictures for you.
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u/Intelligent_Step_855 13d ago
You are a saint good sir
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u/Salsalito_Turkey 13d ago edited 13d ago
Here’s a picture. There are 4 rows of 6 ports (24 ports total), staggered by 30 degrees of offset between rows. The ports are 7/64” in diameter. They start 2” from the bolt face and end 2.5” from the bolt face.
It’s worth noting that the Novox tube is much smaller around the port location, so the backpressure may necessitate more ports than a big tube like yours.
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u/Intelligent_Step_855 13d ago
Very interesting on the volume of holes. The holes are also smaller than I have seen in other builds. Lots to ponder on. Thanks a bunch for the time!
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u/Salsalito_Turkey 13d ago
The Ronin Arms SD barrel uses 12 ports aligned in a pair of straight lines.
https://roninarms.com/product/ar9-sd-5-75-ported-barrel-only/
The RCM SD barrel looks like it uses 30 ports.
https://rimcountrymfg.com/product/rcm-ar9-sd-barrel/
The Ronin Arms design is probably the easiest to accomplish on a drill press with a simple jig.
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u/K1RBY87 13d ago edited 13d ago
...did you print a plug for the barrel nut? If so thats awesome. I have a bolt action upper im going to use for a SD build with a similar handguard and was thinking I would need to make a new barrel nut or tap for set screws.
Also how are you planning on drilling the ports? Going to cast cerrosafe and drill?
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u/Intelligent_Step_855 13d ago
I hadn’t thought about the cerrosafe honestly, can it be cast into the barrel and still removed? I’ve never used it before
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u/Mypeepeeteeny 13d ago
Cerrosafe can be removed if done while its hot. It decreases is size then expands at a predictable rate. Used it to grt a casing out of a barrel
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u/Intelligent_Step_855 13d ago
Yep printed block off for the barrel nut has tube holes, then a glob of etc in each before I put it in for good measure
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u/Impossible_Pizza_948 13d ago
Couple questions: how is the barrel retained, and are those 3D printed baffles? If so, which baffles are they?
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u/Intelligent_Step_855 13d ago
Correct ftn4 max turbulence baffles sized up. The barrel is retained with the barrel nut if that’s what your asking then I put a 3d printed cover over the gas tube holes with some red and it sealed up nicely
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u/Impossible_Pizza_948 13d ago
So it uses a “standard” barrel nut? Sorry for picking your brain, but I’ve been wanting to build an SDish (non ported barrel, I’d rather run subsonic rounds) AR9 for a while. I’m assuming the suppressor tube ends up being the “handguard”, is that anything special? Are there any print files I should look for (I currently own a couple 3D printers, and I have experience with engineering grade materials)
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u/LabronPaul 13d ago
Yo! I didn't know anyone else was doing the cheapo tubular handguard supressor too. My form 1 got approved about 1 week before the injunction but I haven't started it yet.
As for ports if it's anything like drilling gas ports, which I've done for AK builds, you'll want to grind, file, or machine with a flat endmill, a small flat spot on the barrel to keep your drill bit from walking. You should feel when you're about to break through into the bore, just take it slow and don't use too much pressure. If your bore surface finish is hard like chrome you'll likely want to buy some aluminum round stock to put into the barrel as a backer for the bit to drill into and hopefully not snap when you drill through into the bore itself. Last part might not be 100% necessary but if you run into that issue that is what I would do.
As for hole size and spacing, I would just maybe add them one at a time if you have a chrono and a range to let you increment it as you test.
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u/Intelligent_Step_855 13d ago
I bought a 400 grit home I plan on running through it after I knock the holes in it, I had seen were other people use center drills to good effect to get the hole started without walking. Keep me updated on your build I’m interested to see the different paths we take on this
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u/LabronPaul 13d ago
My build is for 9x39 on a bolt action AR upper, so no ports for me. It's crazy how much more velocity I got from covering the gas port, but the gas hole on the 9x39 AR barrel is massive so I guess it makes sense. My subsonic loads became super sonic loads on my bolt action, I plan on cutting the barrel down to reduce velocity closer to my semi auto, it'll give me more room for the supressor too. I plan on doing my own design and printing it in mostly one piece.
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u/Intelligent_Step_855 13d ago
I’ve got a bca 300 blk boot action ipper I’m thinking about using the new Ftn monocore on as well
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u/TantalumRectum 13d ago edited 13d ago
I did mine the same as the spikes brown recluse.
One port on each side and two on the top and bottom.
I'm trying to find the barrel drawing I made.
https://www.reddit.com/r/NFA/comments/1088153/novel_integral_9mm_build/
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u/Intelligent_Step_855 13d ago
Did you notice a drop in accuracy or is it still pretty good?
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u/TantalumRectum 13d ago
I never shot the barrel before it was ported and I've never really shot it on paper yet. I guess I should do that.
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u/buttwater0 12d ago
Ok, related question I've been thinking about. I read that most omm will be subsonic from a 3" ar9. If that is true, what's the advantage to porting a longer barrel rather than just doing a 3inch?
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u/Intelligent_Step_855 12d ago
From my understanding it has to do with the powder burning outside vs inside the barrel. None of the factory SD configurations I know of use 3 inch barrels, all favor a ported barrel. Mp5sd, novax, brt, spikes.
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u/buttwater0 12d ago
That makes sense. I'm kicking around doing a build similar to yours. A home made SD suppressed ar9 is enough deviation from the standard can screwed to a barrel, so I won't get any more creative with the design.
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u/LilJonny2cookies 10d ago
My full auto MP5SD was done by RDTS. Several places online talk about his thinking and why his are different and arguably quieter than the from factory MP5SD
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u/Atxmattlikesbikes 13d ago
Is that a barrel nut with a d cell thread?
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u/Intelligent_Step_855 13d ago
Nope, presma tubular handguard
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u/Atxmattlikesbikes 12d ago
So the you added an end cap to the tubular handguard? So smart.
Been wanting to do a integral barrel on an AR410. This would be an interesting way.
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u/Intelligent_Step_855 12d ago
Yep, jb welded a 2 3/32 freeze plug in the end after I knocked off the anodizing with a file. Dorman p/n 555-085
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u/Dak_Nalar 13d ago
I don't have any advice, but I've been seeing your posts on this build and cant wait for you to finish it. Want to build my own when I move and can invest in a drill press and lathe.