SacramentoGunGuy

Mace, just don't do it. Pick a manufacturer that has some reputation behind it and more experience in the AR 10 space. I cannot begin to describe how much I regret buying a Gibbz 308 receiver set. When I got it back from Gibbz, they fixed the short stroking by boring out the gas port. Now it will eject properly but still has regular feeding issues. Essentially the bolt lug doesn't catch the case head of the next round and instead the bolt drags on the surface of the case and causes the round to feed awkwardly and jam up the bolt, squishing and usually ruining the round in the process. Other people have the exact same issue. I emailed Gibbz and asked what I should do from here and radio silence. They are done helping me with this. I haven't tried having a gunsmith extend the feed ramps into the upper receiver because I've learned that shouldn't be necessary. On close inspection with the rifle closed and the bolt open you can see the rounds ride high enough that there is no way they are hitting the receiver. If you have M4 cuts in your upper but not the barrel extension is where you run into problems, and its a very specific type of stoppage that is different to what I'm experiencing. Plus, if I go cutting into the upper receiver, Gibbz will have a reason not to refund my money when I send this receiver set (or "useless overpriced pile of poop" as I affectionately refer to my $2,000 .308 build) back to them. And really even if cutting feed ramps into the upper did magically and inexplicably fix the problem, I'd still say Gibbz is poop. Why sell expensive billet upper receivers that won't run without cutting into them? For what they charge and the way they describe their stuff as being so high end, an oversight like that would still be unforgivable. I've tried everything and it still does the thing. I've tried different mags, I've tried different combinations of buffer and spring, I tried stretching out the mag springs, I tried lubing the crap out of the BCG, I tried just working through a few hundred rounds to break it in, I tried shooting pushing up on the mag, I tried shooting pulling down on the mag..... It still does the thing. I have come to the conclusion that it must be the receiver set is out of spec. It is the only variable in the parts equation that has an "unknown" when it comes to reliability and compatibility. I'm certain if I put my BA barrel and BCG and JP recoilless buffer system in an Aero M5 receiver set, the God damned thing would do its job. I plan to do just that, but I can't justify pouring another few hundred dollars into this absolutely maddening money pit of a project until after Xmas. After that I will get an M5 receiver set and literally rebuild the entire rifle. I will send the Gibbz set back to them along with a demand for my money back, which I am 100% I won't get. Don't be me. Be smarter than me, and go with a receiver set that has a good reputation. Gibbz 308 receivers are no good.

Thanks for weighing in! I dont mean to be dismissive, but given that I can duplicate the jam by working the bolt by hand slowly, I don't think its a matter of the bolt traveling too fast. I'm thinking either I need to cut some feed ramps into the upper receiver, or one of the receivers is just out of spec and the rounds are presenting too low.

here's another pic showing the feed ramps straight on

Hey 98z5v, I have an update and also a question. So I sent the rifle to Gibbz. They drilled out the gas port, said it was running fine, and sent it back. When I went to fire it, the short stroking problem was resolved, but now I have a new problem. Well, I had experienced this problem intermittently before, but I attributed it to the short stroking. The problem is a jam that I will try to explain. The round starts to go into battery, but is being presented at too steep of an angle so the bullet wedges against the chamber wall. Once the forward motion of the round is halted, and the round is at an awkward angle, the back of the case is pushed downward by the bolt as it travels forward until the bolt is riding on top of the case. The bolt then impacts the case a little below the shoulder. Ill post a pic that shows the end result. I can reproduce this jam when cycling by hand, so it isnt the gas system or the buffer. It seems to me the geometry of the feeding is off and after some research I think I figured out why. The barrel extension has M4 feed ramps that aren't blended into the upper receiver. Not only that, but when you look at the correct angle, you can see a ledge of aluminum where the bullet is supposed to meet the feed ramp. Seems to me, if this were smoothed out and blended, the feeding issue would likely resolve. Ill post a pic of the feed ramp too. What do you think?

Hey 98Z5V, I followed this link and didn't see any other threads about Gibbz G10 issues. Did some searching of my own and o ly found this one. Can you help link me to the other threads on this topic? Id really like to read them because I'm having the same issue.

Franklin, I am having the exact same issue. I am so frustrated with my Gibbz 308 build. I spent a lot of time and money on it and it isn't functioning properly. I have spoken to Gibbz and they recommend that I ship them the rifle for inspection. Hearing that they took your upper for several months and then returned it to you in the same condition makes my heart sink. My saga so far: I put together the build in early June. Gibbz G10 upper with ballistic advantage barrel and ballistic advantage bcg. Gibbz G10 lower with CMMG LPK, Geissele ssa e trigger, Luth AR stock. On first range trip out rifle wouldn't cycle properly. It will barely poop out the empty brass, but fail to load another round. Bang, click. Won't hold open on an empty mag either. Also sometimes when cycling a round, either manually or when firing, a round will just fail to feed, getting hung up on the barrel extension. Tried several range trips, lots of lube, ammo types. All the same. At first I blamed the gas system. So I had a new gas block and tube installed and put in a JP recoilless buffer. Still acting exactly the same. So clearly it isn't the gas system. It seems like there is just something off with the geometry that causes the bcg to slow down and cause feeding problems. I noticed some unusual marring on the bcg that leads me to think the bcg is riding on the side charging handle, causing it to lose velocity and not donits job. But what do I know. Im not a gunsmith. Maybe their upper receivers are just out of spec. I believe someone did say they used a Gibbz G10 lower with a different upper, correct? I am already afraid that Gibbz won't be able to fix the problem and when I do get the rifle back in several months it still won't work, and I'll end up having to tear the thing apart and buy a different receiver set and rebuild it. Ugggggh. Please keep us posted Franklin. I am very eager to hear what Gibbz does on the second go round. I so wish I had just bought a freaking M1A at this point.