New AR

[kingconan]

[IMG] SA_Raven01_logo

Billet Upper & Lower
14.5'' .223 Chamber, DI Carbine Length Gas System.
Surefire MB556K Brake
Samson 12'' Evo Handguard
troy Folding Sights
Geissele Match Trigger
Magpul MIAD 7 UBR
LaRue LT-104 mount with a 2.5-10x32 NXS Scope.

[HaydenB]

Looks nice.

Any more info on the barrel and BCG? (make/specs?)

What led you to the decisions for this rifle?

What is your intended purpose for the carbine?

[kingconan]

Thanks very much.
Barrel is a Bergara from Spain M4A1 profile that I happened to have lying around. I'm based in the UK and build custom guns, just got my prohibited gun dealers license so this is the first semi i have made. Everything up to now has been straight pull.
BCG is a Youngs National Match that I tuned.
I started off small on the gas port, .063 to be exact, shooting 69 grain Lapua Match. It seems to be short stroking with a full mag applied, I'm guessing that there is extra pressure on the bottom of the carrier that is causing it to slow down and the empty case to be extracted but remain in the upper as a live round is trying to chamber. The plan is to increase the gas port size to .068 unless anybody has any better ideas.
Straight pull guns don't care about buffer types so I only have cheap bog standard dpms ones available right now.
Please don't think that this is some sort of advert by the way i'm just interested in learning and talking about these rifles is all. European guns can't compete price wise with US gear anyway.

[wetidlerjr]

Interesting. Great photography, by the way.

[Col_Crocs]

Nice carbine. Cool looking lower... Looks extremely well made.
Dont touch the port... That's standard for a 14.5 carbine. If it's picking up the next round, youre not short stroking. At the moment, it Sounds more like an ejector issue to me.
Could you verify the following...
- what mag are you using?
- ammo, is it 223 or 5.56?
Also, do you have or could you take photos of ithe malfunction?

[kingconan]

Thanks Very Much.

Got a bit of Video if it helps:

http://s620.photobucket.com/albums/t...urrent=Jam.mp4

Mag is a 30Rnd Maglevel PMAG.
Ammo is .223 Lapua 69Gr Match.
It cycles fine with 5-10 rounds in the mag, put 15 or more in it and it does the same thing every shot.
Looks like a double feed when you look through the ejection port, except that the top round has been fired, its made it out of the chamber but not out of the upper. The next round has come up to be chambered and wedged itself underneath the empty.

Got me thinking now, bolt and carrier has had to come back to collect the next round and send it forward so it should have thrown the empty out, so you are right at some stage the bolt is letting go of the brass.
I have a sneaky feeling that I left out the spring harmonics dampener from the extractor, would that cause an issue? (thought it was more for full auto).

Built too many straight pulls you see and they don't need that stuff

Why would round count in the mags cause the effect?

Thanks for the help.

[Col_Crocs]

Test the tension of the ejector... See if it's binding in any way.
Also, Try putting in the insert. Secondly, Do you by any chance have access to an H or H2 buffer?
Here's another theory... It could be that the extractor spring itself is unable to hold on to the brass while the standard buffer is making the weapon cycle to early and/or too fast. The reason being that spring tension alone(without the insert) is not enough to keep a hold on the brass and the weapon is cycling before the casing has completely "relieved" itself of pressure, hence the extractor ends up losing it's grip... It's a bit of a stretch but considering all things are new, it's worth checking out.
ETA: i keep looking at the video and it's most likely an ejector issue. The reason for the issue being dependent on mag round count could be that the ejector is still functioning but on a less than minimal level. Hence, the tension of the fully loaded mag, further aggravates the issue in that it slows the cycling enough to not flick the round out before catching the next round.