Sorry if this is a stupid question but I am not a weapons expert and just started shooting seriously. Recently bought some F1 62grain ammo (1,000 rounds). I specifically bought this ammo because I wanted a slightly higher grain that weren't green tip (although I'm sure the grain doesn't make that much of a difference). Anyway, I got the ammo yesterday and the casing seems to be eroded (very gray looking instead of the brass look). I shot a few rounds off, and the gun smells very gassy when pulling the charging handle back, and to add to that, the charging handle is very stiff after shooting, it was taking me a lot of force to pull the charging handle back even though I only shot off a few rounds to test the ammo out. I'm just curious if the ammo is okay to shoot? I've put some gun oil down in the gun so hopefully that will resolve the stiffness issue.

If you mean they look like this, it's normal.
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Yup, that's exactly how it looks. Thanks.

On the side note. Took everything apart and lubed everything up nicely and charging handle feels a lot smoother. Was probably just stiff after the first shoot because it's a new gun.

Yep. The rifle will break in as you shoot it. The 5.56 ammo for the military isn't polished to make it look pretty.

The discoloration is most likely where the brass was annealed to soften it. They use heat. Otherwise it may have cracked when they necked it down. They don't polish it which is good. It keeps prices down. Like was said earlier just shoot it. Break it in.

https://www.ar15.com/forums/AR-15/AR15-LUBE-POINTS/7-548967/

OP has likely worked this out but for any new guys out there with a new AR---- Take that factory new gun , clean it to get the factory dirt and grit off and lube it like someone else is paying for the oil . Expect it to be a bit rough and stiff for a while and keep adding oil .

Appreciate the feedback guys. It helps a lot.

Run AR15 wet.
Run Glock dryish

That's fair.