Finished a 16" build some time ago.
Bought the barrel used, so no idea as to who made it, but it shoots pretty good.
The upper is a slickside Anderson.
The Lower is from JoeBob's and the Bolt is NFA.
The rifle runs like a raped ape using ETS, Magpul and Glock mags - when shooting FMJ's. I'm talking Tula, Win, Rem, Wolf...all of it.
I've tried 4 different HP's now. Speer, Rem, Prvi and Hornady - all of them fail to feed in any of the mags - excep the OEM glock mags.
When chambering a round, it appears as if the nose of the bullet bumps into the bottom of the barrel extension/ chamber. So, the question is - do I have a barrel or a mag issue? Or both?
I only paid $50 for the barrel, but it's the only 16" 9mm barrel I have at the moment. The carbine will be my "range" gun so the HP's aren't that big of a deal. I can live with only shooting fmj's through it, so this is merely out of interest, as I'm building 2 or 3 pistols for family members as defensive weapons.

Don't mean to hijack your thread OP but finished a build a few days ago with the exact same issues. Feeds Round Nose fine but HP's smack into the bottom of the feed ramp preventing the round from chambering or plain getting stuck on the feed ramp.

Here's some pictures of my issues, maybe yours looks the same as mine OP: Pics of the issue

Parts list:
Ballistic Advantage 8.3" 9mm barrel
QC10 Glock lower
VLTOR MUR upper
QC10 9mm Glock BCG
KAK Industries 8oz 9mm extended buffer
Wolff XP Carbine spring

Haven't shot the gun yet and plan to this weekend so I loaded up some dummy rounds with different bullet designs and experienced what the pictures convey. Round  Nose is fine, Hollow Points a no go. To my inexperienced eye, the bevel on the feed ramp isn't angled enough to allow the hollow points to feed.

I've seen pictures of ramps on other mfg's barrels that have a more generous looking bevel, but it could just be the lighting. Any help would be appreciated as well. Ballistic Advantage told me to shoot the gun first, which is fair, but if it doesn't chamber in the first place... Lol

hope it's clear enough!

Ill grab a pic of the breech in a few and post it.
Like I said earlier...It feeds fmj fine from all mags and will feed HP from OEM mags, but not from Magpul or ets mags.
It's not a massive issue for me, but finding subsonic fmj is not easy!

Looks exactly like what's happening to mine. HP's won't feed regardless of magazine in my case though.

Seems like there may be something different about the mags/feedlips if it works from Glock OEM mags and not aftermarket mags.

Have you looked at loaded mags side by side to see if the rounds present themselves differently in the various mags?