Originally Posted by
okie
Just went and checked DD's site to see what their current port size is. Current port size is 0.075, so either they didn't change it, they changed back, or it was something truly ridiculous that they scaled back from.
Doesn't sound like much, but that's about a 10% increase in diameter, which translates into approximately a 20% increase in area, since area is the square of the radius. Simply put, it's a significantly bigger hole, especially when you figure how much flow increases with relatively small increases in diameter. I think it's like a 100% increase in diameter equals a 1500% increase in flow or something.
The Mk18 at 0.07 is already pretty gassy. They have no problem running 5.56 unsuppressed, in all weather, right out of the box. With a can on it, it can run 223 steel on an H3 buffer and still lock back when shot vertically on a cold day, which is worst case scenario. And that's fresh off the line, not accounting for erosion. Mk18 ports erode very quickly. For the most part, you're going to get the bolt outrunning the mags long before the barrels are shot out, so you have to find a medium ground for port size, because three thousand rounds into it, the erosion is already going to be affecting things.
So why would DD do that? I don't know, but I do know that spec Mk18s, unsuppressed, sometimes won't lock back on 223 even on a hot day. I've found it to be mag specific. On a warm day I can get one to lock back on polymer mags, but not USGI mags. What I also know is that when commercial manufacturers properly size their gas ports, they inevitably get a lot of angry phone calls from customers wondering why their gun won't work right, and they don't like being told that their PMC isn't the right ammo (gosh darnit I didn't pay two thousand dollars for a gun that can't shoot everything!).
It's like I've said throughout this thread, when you buy a gun designed for and marketed towards the commercial market, you're buying a gun made for 99% of consumers, who will shoot it once out of the box, and if we're lucky maybe once a year after that. And as long as it goes bang every time they will never complain. That's just how it is.
I'm not trying to be a dick here, but I feel like the person coming to this site for advice isn't the average troglodyte looking for a safe queen, and I feel like they deserve the unvarnished truth. And hopefully, armed with that knowledge, they will go out and demand better and all of us will benefit, including the manufacturers. I'm positive DD would love nothing more than to have a more educated consumer who could appreciate a properly sized port if it was given to them, so I'm not trying to throw anyone under the bus here.
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