I am using a Milwaukee co2 regulator and am trying to find a washer that will fit between the cylinder and the regulator. The ones I found on the internet said: "Not for use with the Milwaukee regulator".
I accidentally cracked the flange of a Milwaukee nipple awhile back, while tightening it against a permaseal (I tried one this once, and will never do so again - standard nylon washers are dirt cheap and work flawlessly). I drank myself into a stupor out of frustration ...and several weeks later, had the presence of mind to wonder if the rest of the flange could simply be chipped off. 5 minutes of experimentation with a chisel and hammer left me with a (very) roughly flat surface, and I used that regulator for several months afterward with a couple (I refilled the cylinder) nylon washers.
I've since upgraded my regulator - a couple of times - and am happy I did. But that flange is just an annoyance, which can be dealt with via simple tools combined with brute force.
so if I just bought a used 2.5 cylinder and used Milwaukee regulator. it's not a good ideal to use the perm-a-seals, or is it again Ideal. since it's used I want to put a new washer on it, and was going to put it on a 29g quick will be heavy planted, and wondering how long it will last.
The other option is to go to a welding/gas supply shop like Airgas/Praxair and get a new CGA 320 nipple without the raised face. It should run about 10 bucks and some teflon tape. You simply* take off the old nipple and install the new one. Connect up to your cylinder with a regular 320 seal washer and leak check.
*I say "simply," however this may not be the case if the nipple was threadlocked really well in to the regulator body.
See if you can remove the nipple before you bother contacting anybody about a new nipple. Unless my 3M clone (currently in front of me) is dramatically different from the Milwaukee, there are no flat surfaces to use a wrench on, and it's not even clear that the nipple is attached via threads of any sort (size or standard), aside from a hairline crack between nipple and regulator body.
In short, I believe it's a one-piece unit, and there's no possibility of replacing the nipple. But I could be wrong.
In any case, even if it's possible to replace the nipple, getting Milwaukee to send you a couple of proprietary washers is still the cheapest option.