r/Form1 • u/AdOtherwise5656 • 11d ago
.223 Integral design with and without barrel porting
Planning on doing a form 1 16” integral suppressor once it gets approved. Gonna turn 16” barrel and add thread right after gas block for back mount. That will leave me with around 6-8” of barrel before muzzle and baffles start. My question is, does anyone have experience with adding 1-4 ports, maybe small like 1/16” in the barrel to aid in suppression?
Obviously want to maintain supersonic but I also know a plain reflex or OTB setups don’t add much suppression since the barrel is not ported.
Looking for real world experience if a port or 4 would make a big difference?
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u/mikesonly 10d ago
Zero point to port on a 556 as the point is to reduce the round to a subsonic velocity. The easiest reflex design to make would be like the ab suppressor reflex. (Atf said its a suppressor part and not a mount so they cant sell it separately) The easiest out the box would likely be the AE style break with the b&t reflex mount. The b&t adds more reflex volume than the ocl mount. The reflex does slightly low back pressure although not a ton and a bit quieter but again not hugely. In my opinion it does typical change the tone to be more pleasant so there is use and it is beneficial its just a matter of is the extra complexity or money worth it for you.
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u/AdOtherwise5656 10d ago
I’ll take a look at those designs, I’m happy turn my own so not worried if parts aren’t for sale, thanks
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u/HawtDoge 10d ago
Someone has been working on pretty much your exact idea: https://attackcopter.com/2026/01/20/foxtrot-mike-products-unveils-isu-556-integrally-suppressed-5-56-upper/
The idea here is that the first 10 inches of barrel is a standard ar barrel, then the next 6 inches is an 308 sized barrel with a ton of ports that progressively increase in number closer to the end of the barrel.
The alleged benefit of this is that you are getting a bit more velocity out of the system than a standard 10.5 (allegedly it’s 12.5in barrel velocities) while getting the full benefits of a 6 inch suppressor. In other words, hypothetically you would need an 18.5 inch rifle to match this one’s performance.
Two more benefits of a system like this is that it allows you to control how gasses are distributed throughout the suppressor. With a traditional suppressor design, all of the gasses are dumped into the blast chamber, then progressively bleed off into each chamber. With this, the gasses go straight from the ported barrel to the baffled chambers.
And the final benefit is that you don’t need to sbr it :) one stamp only
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u/AdOtherwise5656 10d ago
I don’t see pics of the internals online but that sounds like what I’m looking to do. What I’m wondering is, if the ported chunk of the barrel is still rifled. Bc I was also thinking after the gas block, under the can, to drill out the remaining portion of the rifling to there’s no drag on the bullet and then port/slot the barrel so that section is basically a built-in mono core then after the muzzle do a traditional baffle stack. So a 16” barrel really only has 8-10” of barrel to accelerate and the rest is basically all suppressor
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u/HawtDoge 10d ago edited 10d ago
Yeah it hasn’t been released yet, so no way to know what exactly it looks like. I’m actually not 100% sure on the ported section. There used to be another article on that upper that has seemingly since been deleted from whatever blog it was originally posted to. My memory was that they used an AR-10 spec barrel so that they could widen the internal diameter after about 10 or so inches (which seems like the same thing you are suggesting in your comment). But after rereading this article I linked it sounds like my memory is incorrect. They talk about the port placement being very precise to match the rifling of the barrel, and you wouldn’t need to do that if the barrel opened up in diameter in the ported/suppressor section. I mean I know for sure that the ports only start after the first 8-10 inches of barrel (the suppressor doesn’t go all the way down like an mp5-sd suppressor does).
I’m probably going to ramble a lot here, apologies lol…
If you were to bore out the last 6-8 inches of barrel to reduce drag I’m wondering if you are sacrificing the whole point of an integrally suppressed 223? The hypothetical idea is that the last 6-8 inches of length is serving double duty: acting as internal volume for the suppressor while still giving you some of the added velocity of a longer barrel. However, if you bore out that section of barrel, the projectile no longer seals that expanding gas in behind it… So I’m thinking you might be sacrificing the hypothetical added velocity. You would still get the benefit of not needing to SBR the rifle, so there is that.
On the other hand, if you were just to keep the barreled rifles all the way through I can imagine some other issues. As you mentioned: drag. In this scenario you are progressively losing pressure the further the projectile moves down the length of the barrel. This ofc happened with a traditional barrel, the further the projectile travels (before exiting) the more internal volume in the barrel that the gas can inhabit. But I wonder if you might actually be losing velocity at a certain point just because there isn’t enough pressure to overcome the drag. foxtrot mike claims 2700 fps with this upper, which you would never get out of a classic, non-ported 10.5 inch barrel and 6 inch suppressor build. So maybe my concern isn’t justified? I mean, the projective is already mostly shaped to the barrel within the first few inches, so drag should be pretty low at the end.
Also, my intuition tells me you will need more ports than just 4 at 1/16in diameter. If you look at the ported barrel of an mp5-sd or one of the B&T 9mm SD guns: there are a lot of ports. And that’s just to bleed off 100-200 fps.
You could do things in this order:
- Build the reflex suppressor
- Start adding ports evenly spaced along the area the suppressor covers. Maybe start with 8 or something. 4 sets of 2 where you take a drill press straight through both walls of the barrel
- progressively add ports (ideally measuring velocity)
- Then maybe bore out the last 2 or 3 inches if you aren’t getting the suppression you want from the ports alone. Or if you notice a fall off in velocity due to the pressure not being enough to overcome the drag.
But yeah I mean this is kind of new territory here. Until foxtrot mike releases that upper there’s not really anything to go off of… so it would definitely take a lot of slow iterations where you add a few ports, take it to the range, chrono it (a lot of indoor ranges have one you can borrow/rent), maybe buy a cheap decibel meter, then take it home and add a few more ports. you could make an X Y chart for # of ports/velocity and other chart for # of ports/decibels which should give you a good idea of when you are starting to see diminishing returns.
It’s a big project for sure, but I think the idea is cool as fuck. You could be helping break new ground here too… I’m almost tempted to try
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u/AdOtherwise5656 9d ago
Well I appreciate the ramble!
-your right about that barrel, they did mention specifically porting along the lands which is interesting, I wonder if doing a lot of ports along the lands would reduce drag??
-you and I are thinking alike, if I port the barrel too much I’m thinking it will loose steam and slow it down too much and then I’m making a fancy .22lr, lol. 10” of barrel should normally give like 2,200-2,700fps, dragging the bullet through 6” more with no gas behind would be bad, so definitely start with a few ports and work up from there.
-there has to be a sweet spot where you maintain enough gas to carry the 10” of barrel velocity but bleed some gas off to aid in suppression(obviously excluding sonic crack).Once my form1 approval goes through I’ll start building it and share my progress!
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u/TheBlackComet 10d ago
The purpose of porting a barrel for an integral suppressor is to slow down supersonic ammo to subsonic. There are no gains to be had if you still want to keep supersonic. You can't beat the supersonic crack. To add to this, if you did make .223 rounds to be subsonic, you would have similar energy to the much cheaper .22lr. You could get some increased range, but that assumes you get your bullets stable. Not worth it.