ShadowAviator

The cam pin change was just something I have done on other ARs. It is supposed to replace, and perform the exact same function, as the normal cam pin. The head is just rounded a bit were it touches the upper to help reduce wear. Its not really a race gun part. It certainly should not complicate anything, however they seem to have machined the diameter too small. Other BCG makers I have talked to seem to use the 0.371" as the normal cam pin size, so why Lantac is using 0.366, I don't know. I told them of the issue and they are looking into it. Again, it is supposed to just be a replacement cam pin. Anyway, I have resolved that issue by going back with the original cam pin. Nothing else has been swapped out. We have already discussed the recoil and gas systems on the first page. I think anything that wasn't mentioned I have already checked myself using info from other threads. (gas tube length for example) I think I will let this discussion end for now. For the most part, I only started this thread to double check what I already knew and learned on here. In that regard, everyone has been very helpful. On the failure to extract issue, I will see if changing the cam pin may have helped in some way. From there, I will research and troubleshoot on my own. As 98Z5V said, trying to troubleshoot an issue over the internet is difficult. Even if we review the build info again, I think I will only be wasting everyone's time. I think I can work at it on my own for now. If I can't figure it out, we can comb through the details then. Thanks again for everyone's input. 98Z5V, thank you for taking a look at the extractor picture and letting me know about the square ejector pins.

I really didn't expect the lantac cam pin to be .005 smaller. It felt like there was too much play when I was cleaning them, so I decided to check it with the original toolcraft cam pin.

I am confused, I believe I gave all of that info in the first post on this thread. I think all the info from the waterboarding thread was covered in the first page of this thread. I didn't think the lantac cam pin was a race gun part, its simply not supposed to wear as much on the upper receiver. Honestly I forgot that I had swapped it out.

I will holler at them in the morning. I want to know about those cam pin diameters, too.

I have considered polishing the chamber a little bit at some point. Save that for last though.

I dialed the gas back until it would not lock the bolt back and was still having cases stay in the chamber sometimes.

The lug "wear" might be normal. Looking closer, I can see some coating on the angled part. Do they normally come with a beveled corner like that? This may seem unrelated, but would anyone know the cam pin diameter? In thousandths? I had put a Lantac domed cam pin in to help with wear on the upper reciever. It was something I have done on my AR-15s, though looking at it now probably not needed. Anyway, the Lantac pin measures 0.366, but the original toolcraft measures 0.371.

Do these wear marks at the corner of the lugs look normal?

Not KAK round, but seems smooth. I don't notice ejector marks on brass.

Tubbs flatwire spring. Cleaning BCG now, I will try to get a pic.

Sorry, I just noticed I didn't describe the issue. The cases are being left in the chamber. There is plenty of gas to cycle the action and lock the bolt back. It would try to feed the next round, but would jam since the spent casing is still in the chamber. I would clear the mag out, and slam the bolt home on the spent casing and then it would extract. Usually took a little more force than normal on the charging handle to extract at that point.

Could the extraction issue just be that it needs a little breaking in?

50ish rounds through it so far. I don't think it is a "breaking in" issue though, at least I don't think so. I didn't really think too much about the chamber. I cleaned the barrel before shooting, but didn't really think to clean the chamber. Sure would be nice if that were the issue.

I appear to be getting some failures to extract. Seemed to happen with various ammo, from whitebox M80 to different boxes of hunting ammo I had. I can't remember if the FGMM had issues or not. Barrel and bolt headspaced okay. Bolt is the double ejector type. (Toolcraft from Arm or Ally) I had disassembled the bolt for cleaning before ever shooting it. Everything seemed to function fine. Ejector went in smoothly, no burrs on extractor. Extractor springs were the "spring in a spring" type with an o-ring. I did notice some marks from the extractor on a case rim, so I thought maybe overgassed (shouldn't be, but worth checking). Gas block was wide open, so I starting closing it down. Gas was low enough to not lock back on empty, and I was still getting some failures to extract. My next thoughts are either the extractor in some way, or a tight or rough chamber that didn't want to let go. For now I plan to get another extractor (even if I don't need it). Any suggestions on a good brand to get an extractor from? Also plan to check the chamber as best I can and make sure its clean. Any other thoughts or suggestions? I will be pulling the bolt apart again to look closer at everything.

Just to clarify, this is the 308 AR barrel not the barrel for my Tikka.

Heres a pic of the barrel.

Yeah, I will give the Tubbs a try. I wanted to get the gun up and running reliably, however I love to tinker. Thats why I like ARs. Once this rifle is done, the next project is to rebarrel my Tikka T3x to 375 Raptor. After that, who knows.

I think everything looks good. The Tubbs spring should work, the buffer weight seems appropriate, everything measures out okay. Now I just need to find and shoot the crappiest ammo I can find, and then come back here to complain about it not working.

Forgot to add that the gasblock diameter is 0.875".

Just thought I would post some additional info. The receiver extension depth seems to measure no more than 7", maybe under 7". Didn't have a super exact way to measure. Checked the distance from bolt face to the bolt catch, and appeared to be between 3/16" and 1/8". Also the gas port size on the BSF barrel appears to be slightly greater than a 3/32" drill bit (0.09375). 7/64" drill but would not fit, so I would assume its close to 0.096".

That's what I was wondering. Thanks for the clarification.

When you say heavy buffer, do you mean the ~5.4 oz one?

I will have to measure my spring. I know I can lock the bolt back with my Tubbs spring, so the one I have appears to work with the 2.5" buffer.

Did a little checking and my Tubbs spring is stainless and the coating is a dry lube of some sort, I believe. I might give it a go for now. Some don't recommend the flatwire springs. Why is that?