Extraction issues with a C308 (Cetme)?

[lsudave]

This isn't a complaint, it's an observation and I'm wondering if someone might have insight into what's happening;

I picked up a Century C308 with wood furniture just before Covid tore our lives apart. Decent price, $600.

Here's what I've noticed about the rifle in the past couple years- front sight post was off, I had to dial it all the way over to the right to get it accurate. Seems ok now, groups ok. Not an issue to me now.

Extraction:
Steel, Red Army and Tula. 100% with very strong ejection. These are the cheapest rds I have, and have been the majority of the ammo I shot. The gun loves it.

Brass- Armscor 308 (got it from Ammoman, in plastic bags, when they sold "loose ammo" on sale. Obviously we're not going to see this again anytime soon). Also, Korean surplus 7.62x51, from the 80's.
I'm getting a relatively high rate of failed extract/eject with these, maybe 2 in 20 (several a mag). Sometimes more, sometimes a full mag runs fine. I'm not ripping the case rim. I see the striations from the fluted chamber on the case, dark marks but not really noticeable to touch.

I have read the concern about steel making a dirty chamber due to gas blow-by, and brass then sticking. My extraction issue with brass does seem to be "sticky", like it barely comes out of the chamber and doesn't clear the ejection port before the bolt comes home again.
NOTE- I've tried cleaning the chamber thoroughly, and then going exclusively brass, to avoid this; it doesn't seem to help or hurt.

I can shoot steel all day, with a dirty gun, never a problem. If I didn't know the gun was a NATO design (with NATO using brass), I'd swear it was designed to run steel. You guys have any insights into this, what I might do to improve the brass function? Or, should I just stick to steel since it's cheaper anyway?

 

[adcoch1]

My old CETME loved steel case ammo. I had mixed results with brass. Some commercial brass is too soft to use in the fluted chamber, and I'm betting that the loose brass ammo was mixed production commercial ammo. No way to scientifically study it for reliability. If I was you I'd just run steel case if your gun likes it.

 

[wiscoaster]

Brass sticking in the chamber, but not steel, right? Brass cartridge expands and sticks to chamber and throat walls that aren't smooth. What do your brass cartridges look like after you get them out? If there's a "fuzzy" or "scored" look to them then that's what's happening. Maybe you think you cleaned the chamber, but didn't do it well enough and or didn't go deep enough. The chamber might be cleaned of carbon but still have pitted walls, providing a surface for brass to stick to upon expanding.

Try vigrously Flitzing the entire chamber, including throat, right into the beginning of the bore.