6ARC feeding issues

[hwy1strat]

I’m not an AR-15 guy but I picked a SanTan tactical one in 6ARC. I cannot get this thing to load a single round. It will not feed even with me just closing the bolt. I have reached out to the company but they won’t get back to me. I have tried duramags and ASC mags and it’s the same issue from both. I have attached photos of how it jams every single time it cycles. Does anyone have an idea of what I can do to resolve this issue? I don’t think it’s a gas issue because it won’t feed even when I release the bolt from the bolt stop or rack it. I feel like it’s a magazine issue so I just ordered some 10 round duramags since most people on the internet seem to have success with those. Maybe it’s a buffer spring issue? Anything I else I can try?

 

[RockAndSage]

SanTan are some pretty good guns, and it's disappointing to see this happening to you. That said, the first thing that comes to mind is a geometry issue, between the mag's feed angle, the length of the bullet, and the feed ramps. Keep in mind this is only theory without seeing the gun up close and fiddling with it through the malfunctions.

Your first instinct is right on - changing mags. I'd also suggest going to Geissele's website, and picking up 1 of their thirty rounders. What seems to be happening is the feed lips are too long and/or are at too shallow of an angle, and the lips/follower are keeping the case head stuck down in the mag too long - jamming the bullet too high against the chamber wall, while the BCG is pressing the case head forward, jamming the casing against the feed ramp and its sharp corners. Some .45 ACPs have a similar problem, where the feed angle vs the width/length of the cartridge just ends up being too steep - and the bullet jams up against the chamber wall instead of slipping right in.

If changing mags doesn't resolve the issue, the next step would probably be polishing the feed ramps down a bit, taking off a little material on their very top corners, to reduce the overall feed angle. That's something you'd want to have a gunsmith do.

 

[ARK_Ginger]

Since you said you’re not an AR guy, how are you charging the rifle? I’d wet the bolt with oil first, then make sure you’re allowing the charging handle to come all the way to the rear and let it go. If you hold onto the charging handle while it’s closing you could cause this issue. I’d also try with a partially loaded mag first.

 

[RockAndSage]

Since you said you’re not an AR guy, how are you charging the rifle? I’d wet the bolt with oil first, then make sure you’re allowing the charging handle to come all the way to the rear and let it go. If you hold onto the charging handle while it’s closing you could cause this issue. I’d also try with a partially loaded mag first.

Lubrication and enough velocity for the BCG in charging/cycling are the answer for about 90% of shooter-related AR malfunctions, yes. But in this case, take a look at the damage to the casing - it's getting jammed against the feed ramps pretty hard.

 

[ARK_Ginger]

Lubrication and enough velocity for the BCG in charging/cycling are the answer for about 90% of shooter-related AR malfunctions, yes. But in this case, take a look at the damage to the casing - it's getting jammed against the feed ramps pretty hard.

I’ve experienced similar in my 6arc build at the beginning. Ended up having to return the ASC mags to midway. Duramags have worked great though.

The shape of the case tends to exacerbate getting caught on the feed ramp as well

 

[hwy1strat]

I’m bringing the charging handle completely to the rear and releasing it. If anything the issue is the bolt has too much velocity. If I control the bolt closed, the round has enough time to eject from the magazine and then feeds perfectly. I tried some different weight buffer springs from some other rifles I have and it changed nothing. It mostly seems like the feed lips on the magazines are too long. If the round could eject from the magazine sooner, it would be able to enter at the appropriate angle. I’m seriously tempted to start cutting the feed lips to see if that works

 

[Luked]

Had a 350 Legend upper do the same thing to me.
I just chalked it up to a crap fround for an AR. But the 6Arc is perfect for the AR platform.

I did all kinds of things for my 350L from polishing the chamber, Polishing the feed ramps, 3 different kinds of mags. Even got the dremel out and ground the feed ramps down. Nothing worked. So i put it back in the safe and havent touched it again.
Was planning on going to a 6 Arc myself on the spare lower I have.