N/A 3/8-24 foster QD fill nozzle??

Very fair questions. I'm a hobby Machinist and actually put a thread pitch gauge on it and measured the diameter. I have examples of all of the common ones and none of them measure out similarly nor even come close to fitting. It clearly seems to be 3/8 - 24.
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This is the OE fill port for a .25 Cal Gauntlet Gen 1. It's a 3,000 PSI tank regulated to 1900 PSI.

It also only has a simple floating needle, one-way check that does not have a spring or retaining nut. The threaded section is also significantly shorter than the standard ones and has an o-ring at the thread termination.

I did find them online but they were always in places like AliExpress or some other questionable direct Chinese or India Outlet.
 
FWIW, I did reach out to Umarex today after I posted and they are going to send me the part number that it shows in their system. I was advised that I could purchase more if it fits but I would still like to know of a manufacturer or retailer who carries a higher quality one. To be honest, this one looked to be plated versus stainless, or at least a low grade stainless
 
I have zero experience with the Gauntlet, and that has a strange look to it,, almost looks tapered in the photo [camera angle?]
well at least you can get the factory replacement , sorry I am no help,, maybe a Gauntlet owner with the same issue could jump in
I wonder if, you could edit the title and add Gauntlet to the title to gather more attention from owners, or start a new thread
"seeking Gauntlet fill fitting replacement, USA source"
 
No worries, I very much appreciate your willingness to even attempt to assist.(y)

The 1st, 2-3mm of the thread is relieved and with a prominent smoothing radius as one would expect for a seal mating arrangement.

Its peciliar as there is no seal seat or material in the regulator where this screws into. I don't know how to determine the date of manufacturer but I can't help but wonder if this was a "covid gun" that received non-standard parts in favor of available ones??

A great point about the title beaconing to fellow owners or Gauntlet insiders. In full dislosure, my very first post here on the forum a few weeks ago did just that. I didnt receive any responses and intentionally left it out this time, out of speculation maybe this rifle/brand isnt appreciated here?😐
 
I certainly shared your skepticism and that's why I bought several of each of the common sizes. None of them are even close to fitting or matching the thread pitch, including the 10mm. The 10mm was over 0.020" larger in diameter than this one.

Worth noting, 3/8-24 it is actually a fairly common size for pressure-type fittings, at least here in the US.

If I were making a modification to 3/8 threads to 10mm on something that was just holding two non-critical things together, I would not be opposed to doing that.

My concern is how much that may weaken the threads on aluminum that I'm not certain of the alloy and that is containing 3,000 PSI. I'll overlay the two thread dia/pitches on AutoCAD and look at it though.

Ironically, The Gauntlet in 22 cal I have is 1/8 NPT. If this 25 Cal didn't shoot so darn well I'd probably just replace the regulator.
I'm also entertaining the thought of Machining a reducer bushing and opening up that hole to accommodate it. Have to look real close to see what types of clearances there are in the internals.