As with anything a certain amount of due diligence is sensible. It certainly wouldn't be smart to get a hose that isn't rated for the pressures you would be subjecting it to.
The hose listed here is the first one that popped up for me at Amazon when I Googled "replacement grease gun hose"
https://www.amazon.com/OTC-24-Grease-Gun-Hose/dp/B00EVPLUSGDescription states it has a working pressure rating of 5800psi. I believe most of them would be rated higher than 3000psi
When I was searching various sites that make hydraulic hoses most of what I found in the small hose category were rated at 3000psi. And for the higher pressures it was looking like 3/16 was the smallest I could get unless I wanted some other kind of tubing that appeared to me to be more of a plastic.
Although I found a few combinations that I I felt comfortable going with - shipping would have made it
More sensible to spend $35-40 for one of the micro bore hoses on airgun sites.
I didn't track down the Internal diameter of any of the pre-made hoses like in the link, but I figured that if 1/8“ fittings are standard I would gamble on the inside being being less than 1/4 inch.
I've not done any calculations at all regarding hose volume. Indeed they may not be practical.
Thank you for pointing that out Alan. I'd bet that since you did mention it you have done the calculations and it is not practical.
Quite frankly after all of the time that I spent searching and researching fill adapter components I would have been better off to have just purchased a complete adapter assembly. But, I like to research and tinker so.... I did.
Anyway - if you are looking for another option, replacement lines for grease guns are something that may meet your needs. It's always nice to have options, even if some aren't very good - causes you to at least think a little bit.
A friendly place to share one's interest in all things airguns.
