Diagnose malf

[17K]

What causes this? It's happened twice in the past 1K rounds.

Happened on reload from bolt catch

Okay Surefeed loaded to 28 rounds
Geco 55gr (Swiss)

Daniel Defense barrel
Colt BCG
Aero or BCM upper receiver
VLTOR A5 kit
LMT lower

[Circle_10]

Do you know if it was the same mag both times?

My guess is a magazine issue, like the feed lips aren't retaining the rear portion of the cartridge properly as the bolt comes forward to strip it out of the mag, leading to the round being misaligned as it's pushed toward the chamber. However I don't have even a fraction of the malfunction-diagnosing experience of many members on this site so I'm more interested in what they have to say on the matter.

[MSW]

Do you know if it was the same mag both times?

My guess is a magazine issue, like the feed lips aren't retaining the rear portion of the cartridge properly as the bolt comes forward to strip it out of the mag, leading to the round being misaligned as it's pushed toward the chamber. However I don't have even a fraction of the malfunction-diagnosing experience of many members on this site so I'm more interested in what they have to say on the matter.

This, most likely.

[Coal Dragger]

Time to number your magazines if you haven’t already. Write down the magazine number when you have a malfunction, then plan on fixing or ditching that magazine.

[gaijin]

At the range when I have an obvious mag caused issue, I stick a round in it backwards and throw it in the range bag.
Easy to keep track of.

[17K]

I am guilty of not numbering these mags. I starting using this group of ten in November and they've shot up a little over 3K rounds. I've had a few double feeds, but not where the case was backed out of the ejection port.

The buffer spring is the original VLTOR and has probably 6K on it.

[Circle_10]

Okay Surefeeds are generally pretty decent, probably the best GI aluminums as far as I know. You may have one or more iffy mags though from the sound of it.

You can try taking your buffer spring out of the receiver extension and measuring it to see if the length is still in spec.
For a carbine spring it's in spec if it's between 10 1/16" and 11 1/4", unless for some reason it's different for the VLTOR. Your problem doesn't sound like anything to do with the buffer spring to me though, but after 6k rounds there's no harm in checking it.

[17K]

Feedlips measure about .438" across with no visible defects.

This one is hard to pull bolt out of battery. I don't know if that could indicate something else.

[26 Inf]

I've had a few double feeds, but not where the case was backed out of the ejection port.

You say double feed, is there another round in there someplace that we (at least 'I') cant see?

Did a round fall out through the magwell when you removed the mag?

What followers are in the mags? The grey one's?

[MistWolf]

I've had a few double feeds, but not where the case was backed out of the ejection port.

What do you call a double feed? If by double feed, you mean the rifle tries to feed two or more rounds from the magazine at the same time, that's a magazine problem. Toss the mag and replace it with two new ones.