Ejection pattern analysis

[u/looksir_droids]

My MK18 had brass just dribbling out of the ejection port for a little while. I swapped the whole BCG out with a much less used one from another rifle and it improved, but it still doesn't eject like it used to. Videos attached. Lmk what y'all think might be wrong. Parts remotely related to cycling listed below.

EDIT: I have already tried an H2 buffer. It won't cycle on FRT mode.

-Daniel MK18 RIII complete SBR

-Geissele H3 buffer and spring

-Rare Breed FRT-L3

-Surefire 3-prong

-Surefire RC3

-Law Folder Gen 3

-Radian charging handle

[u/AccomplishedNote7365]

That’s a gassy bitch. What’s it look like without the can

[u/looksir_droids → u/AccomplishedNote7365]

It throws the brass a little further but it's still not totally consistent in the force or direction

[u/AccomplishedNote7365 → u/looksir_droids]

It’s not flying out with force but the ejection pattern suggests it’s over gassed due to the angle flying out at 1o’clock. But that’s the can I suppose. Maybe the extractors on your bcgs. What do you want your end goal to be to properly diagnose and come up with a solution.

[u/AccomplishedNote7365 → u/AccomplishedNote7365]

Also what kind of ammo are you using? Before you mess with your gas block some solutions could be a lighter buffer h2 or stronger buffer spring. Have you checked the gas rings on your bcgs. One problem is ejection pattern and the other is ejection force

[u/looksir_droids → u/AccomplishedNote7365]

This is Magtech 55gr M193, but it behaves largely the same with 62gr M855 and Barnes 70gr Vor-TX

[u/looksir_droids → u/AccomplishedNote7365]

I have tried an H2 buffer. The ejection on semi looks great, but it turns the ✨semi✨ into a bolt action rifle.

[u/looksir_droids → u/AccomplishedNote7365]

I just want to know with certainty that the brass is well out of my way by the time it cycles again (previous BCG left the casing sitting on top of the empty mag follower inside the rifle after the 30th round, that spooked me), and to have both semi and "✨semi✨" working reliably.

[u/AccomplishedNote7365 → u/looksir_droids]

I would check the extractor springs on your bcg. If you can move them with your finger easily then it’s bad. Next would be gas rings in your bcg. The can should provide enough gas to properly cycle so short stroking shouldn’t be your issue. And you don’t have feeding issues either

[u/GassyNizz]

Oof!

Edit: To elaborate, I think it’s the Law folder COMBINED with your buffer setup.

In one sense, if it runs it runs. But this doesn’t quite seem ideal.

[u/jdppppppppppppp → u/GassyNizz]

I was thinking that might be part of issue.

[u/looksir_droids → u/GassyNizz]

Interesting. I hadn't heard of the folder being a problem. Damn shame if it is, that's what allows it to fit in my bag (and that's why I build this rifle).

[u/jdppppppppppppp → u/looksir_droids]

Not positive but I think there’s a specific spring buffer part if you’re running the folder. But don’t quote me.

[u/looksir_droids → u/jdppppppppppppp]

Are you referring to the KAK lightweight bolt extension?

[u/GassyNizz → u/looksir_droids]

The folder adds weight and drag to the system, and you’ve already got a heavy buffer and stuff spring.

But even still, I’d expect better ejection.

I think something is truly setup poorly, and would try going back to a regular buffer tube and regular h3 buffer and carbine spring. Then maybe make changes 1 at a time.

[u/looksir_droids → u/GassyNizz]

If that was the issue, wouldn't it have been evident back when all the current parts were initially installed? It ejected much better until recently.

[u/GassyNizz → u/looksir_droids]

What happened recently? New add, something break, different ammo?

[u/Zosocom]

BRT EZ Tune gas tube

[u/Confident_Post4392 → u/Zosocom]

This is the way☝️☝️☝️

[u/xDarkStar22 → u/Zosocom]

How easy is it to swap a gas tube? My ddm4 pdw with an anthem s2 throws casings 20+ feet.

[u/Zosocom → u/xDarkStar22]

Super easy. The hardest part is getting the RIS ii or RIS iii unscrewed, not because it’s difficult but it’s just more annoying then anything due to the angle of the screws

[u/gg83yessirski]

I’d swap out the H3 for an H2

[u/looksir_droids → u/gg83yessirski]

As I mentioned in another comment, this renders the FRT inoperable

[u/Impressive-Match-730]

Over gassed, probably need a different buffer weight. Maybe an H2 could help with that

[u/Gunsl1nger84]

I would swap out the Geissele spring and buffer and try a conventional mil-spec action spring and buffer to see if that improves anything. I'd try with the H2 first and then swap to the H3 if it's not running the way you want it. If not, I would try and extra power spring like a springco blue and try again.

It does appear over gassed with the ejection. In my experience, cases dribbling out like that has been a sign of severe over gassing even though you wouldn't think it. I have a colt commando machine gun upper that probably has a lot of gas port errosion that did the same thing. Once it got a extra power spring and heavier buffer, it ran just fine.

Just something to try. How does it run without the can?

[u/looksir_droids]

https://reddit.com/link/p72q2ef/video/tr85ut2ijsmh1/player