DDM4V7P FTF

[Caduceus]

Also, same magazine, or multiple?

Mods, plan on locking this until it's resolved by DD?

[ReCh5048]

So just to be clear here. You are getting malfunctions with subs and supersonic ammo? What brand of .300 Blackout ammo are you using?

You should actually be conducting a lock back test as first mentioned by Mark5pt56.

Internet/Long Range diagnosis is hard. I would allow DD to thoroughly check the weapon and make sure they know what ammo is being used, etc...

I was getting malfunctions while using both Hornady Black Amax 110g and Winchester 200g. Rifle was sent off this morning. Hopefully I hear something back next week.

[ReCh5048]

When I first contacted DD with the problem they suspected a magazine issue. They shipped me a magazine specific for a 300BLK. When the problem occurred with that mag they had me ship it back to be inspected.

[ReCh5048]

Gun as been fixed and is in the mail. Here’s the DD response.

“Inspected. Replaced the SB3 brace/tube with a DD pistol tube. Replaced the BCG (gas key leaks) and polished the feed ramps and chamber. Using the supplied mags, test fired 80 rounds on 125gr. and 220gr. Remington. Half suppressed. Had zero issues.”

Seems like it had a leaky BCG. Now my question is, would the SB3 brace/tube cause a FTF over a DD pistol tube? Or was that more for the legality reason for an SB3/Law tactical combo?

Excited to get my rifle back!

[thegreyman]

Interesting. I have a DD M4 V7 - no problems whatsoever.; I replaced my SB3 brace pistol tube with a DD Factory tube because SB3 Tubes had smaller diameter than DD tubes, and
I like DD parts.

[everready73]

No, in actuality he took the right course of action and DD should make it right.

I acknowledged him sending it back. That's what I would do first too.

It could still be over gassed even if fixed and an insert would be a good idea if so imo

[MistWolf]

This type of malfunction is not directly caused by over gassing. It's caused by weak extractor and/or ejector springs. The dents on the case mouths are from catching on something because they are not being properly rotated out during ejection. The empty impedes the BCG as it's is trying to feed the next round in the chamber. This causes the bolt to override the base of the new round. Over gassing places extra stresses on the springs, exposing those springs which are only marginally functioning. But if the springs are good, the AR would need to be extremely over gassed to start malfunctioning like this.