US Military green patrol bag on JMT

When in the Sierra will help you get a better answer. May? August?

I said I wasn't going to forget to list the month too…July 11 to 30th

You might check on who rated the sleeping bag for 30 degrees. You might not be able to trust some shady seller, but you might trust an independent reviewer more.

An old rule of thumb is that you ought to have a sleeping bag rated for 10 degrees F better than the cold temperature that you expect. You might slide past that if you have plenty of warm clothing that could be used to augment the bag.

The south end of the JMT is higher and colder than the north end.

–B.G.–

It's the official US Military rating BUUUT only if coupled with The GI Issue base layers ,I just read. And I think you made a good point…I could probably swing it on the northern half but wld probably be cold on the latter half of the journey

I'm no expert, but I did spend one entire winter sleeping in an Army sleeping bag.

–B.G.–

I may be wrong, but I think the US Military ratings are survival ratings. Survival rating meaning you can lay in it for 8 hours without getting hypothermia.

I have used the patrol bag and it's not a 30 degree bag. More like a 50 degree bag. If it's get near freezing and you are only wearing base layers, most people would not get any sleep at all. Using those bags in the high sierra will be a disaster.

If you need a couple bags that aren't overly expensive here's what I would do.

First, sell both of the USGI bags on eBay or wherever. They WILL sell. Bushcrafters and survivalists love those things. Then with the cash from those plus a little extra, but two Kelty Cosmic Down 20 sleeping bags. I haven't used one before, and I've read mixed reviews about them, but it should be warm enough with proper layers and it is both light enough, and cheap enough.

And if you have no need for them after the trip, Just resell. Yeah you'll probably lose a LITTLE money, but selling those GI bags helped you buy them in the first place, right? Lol

Anyway, sell the GI bags, buy some cheapER decent down bags, use those on the trip, resell afterward if need be.

I honestly believe that is your best bet. Have a GREAT hike. Hope to get out there someday I the future.

Sam

Having used the current Army sleep system… yeah, that's a thin bag. That said, I'm not familiar with the JMT in July, but I don't think I'd use it for high-elevation stuff around here (Colorado). I suspect that the thicker outer bag would be more the ticket. Both together are for severe cold.

The military emphasizes toughness over weight.

I'll agree that the Kelty Cosmic is a decent cheaper down bag for this use. One of my hiking buddies has one as his 3-season bag. It's not really a 20-degree bag (at best 30) but sufficient for 3-season in most places.