kazuaki

I've looked at pictures of other 308 lower including those posted above and verified that the buffer should protrude a bit. So, the buffer retainer hole in my lower is out of spec. I sent Juggernaut pictures, but I can see the ones on their webpage even look like that. Funny thing is the buffer issue isn't even the issue that led me to start this thread. It's the pierced primer issue that is a bigger concern to me. I'll have to get back to the range and see if my bolt catch fix will resolve that.

Is this what you mean?

Here's a picture of some of the primers. Left to right, Eagle Eye > FGMM > Perfecta. Notice the Eagle Eye has the hole in it. Also, some of the brass has a pretty noticeable scratch/smear mark from the ejector.

When the BCG is in battery, the back of the BCG is flush with the rear of the upper receiver. I believe that is how it should be. Can somebody break open one of their LR308's and tell me if the face of the buffer protrudes from the lower when resting against the buffer retainer? Here's a picture of my BCG in the upper:

survivalshop, the bcg does not touch the buffer at all when closing the upper. The buffer face is perfectly flush with the lower. I think it should be protruding a bit when resting on the retainer. I'm pretty sure they put the retainer hole in the wrong place (Juggernaut's doing, not mine). That being said, I'm not certain it is related to my original issue.

survivalshop, thanks for confirming the protrusion measurement. I know that having to machine the bolt catch is not ideal, but it was only .025" off the back face of it. It's still just as tall as it was before, so I don't see any other issues. I wish I didn't have to do it though. Now that I've discovered the issue with the buffer retainer (that comes machined already, not done by me) I have lost some confidence in the rest of the lower's quality control.

OK, more info I just discovered. I'm fairly certain that Juggernaut drilled the buffer retainer hole too far rearward. If you look at the first picture, you can see the buffer sits perfectly flush with the lower. Shouldn't it stick out a little, so that the back of the BCG pushes on the buffer and takes tension off of the buffer retainer when closing the upper? In addition, you can see the damage to the buffer from slamming into the retainer while firing.

Sorry, forgot about the ammo too. I used 3 types of ammo: Perfecta 7.62 147gr from Walmart, Federal Gold Medal Match 7.62 175gr, and Eagle Eye 308 175gr. The Perfecta primers were intact, I suspect because they are harder maybe. The Federal had 1 or 2 primers pierced and the Eagle Eye had about 75% pierced. That being said, the Eagle Eye was also the last ones I shot.

Sorry, for the lack of details. AIM Surplus BCG Wilson Combat TTU 2-stage drop-in trigger group Pretty sure it was run wet enough. I'm curious, how could the extracor spring/o-ring being stiff cause this? Just to be clear, there were no failures to extract or eject. I'm 100% positive that the hammer face was sitting on the bolt catch. I'm pretty sure is should be resting on the firing pin only, correct? I can confirm that when I dry fire it now, the bolt catch does not bind and can be moved freely. So, I think I'll be getting full power to the firing pin now. The big question that remains for me is about the pierced primers. Can somebody confirm the .055" firing pin protraction is acceptable? Also, can a free-floating firing pin (not being held against the primer by the hammer) allow the primer to blow a circle out the back into the bolt? Thanks again for the help.

** Sorry for the long post, but I'm trying to be as detailed as possible on what seems to be a complex issue. ** Hi all, I just completed my first LR308 build. I have previous experience with several AR-15 builds, including a few 80% lowers. For this 308 build, I used a Juggernaut Tactical upper and 80% lower. After completing the lower and assembling the rifle, all seemed to be good. Today at the range, after firing 30-40 rounds, I had a couple of FTF due to light strikes. I stopped and decided to pull the BDG and look things over. When I tried to remove the firing pin, it was pretty well stuck in the bolt. I had to pull it out with a set of needle nose pliers. As soon as it came out, about a dozen small round metal bits came pouring out of the bolt tail. After consulting with another shooter, we went and looked at my spent brass. Many of them had a hole clear through the primer. I guess the piece punched out of the primer was flying back into the bolt through the firing pin hole. It eventually bound up the firing pin enough to cause the FTF's. So, I called it a day and headed home to troubleshoot. I measured the firing pin protrusion and it is about 0.055", which I believe is OK. Can anyone confirm that? I found a post on another forum, where a guy had issues with light strikes due to the hammer hitting the bolt catch, thus not putting full force into the firing pin. I checked mine and, sure enough, with the hammer dropped, the bolt catch is binding. The hammer rests on the bolt catch, not the firing pin. Obviously it strike the firing pin hard enough to send it flying forward and hitting the primer. Most of the time it ignites. My fix for this was simple, I machined a very small amount (0.025") off the back of the bolt catch. Basically, I removed the small lip on the rear of it. I can now drop the hammer and still move the bolt catch freely. Success, right? What still bothers me is the pierced primers. Assuming the pin protrusion mentioned above is OK, what could cause that. Could the fact that the firing pin is not being held firmly against the primer allow the primer to blow out? When my firing pin struck the primer, it would immediately fly back t the face of the hammer, which was at least 02" away. Could that cause the center of the primer to blow out? I know the easy answer is to go back to the range, but with life getting in the way, that's not so easy :) So, what do the expert think? PS, can somebody take some accurate measurements of an LR308 firing pin? I'd love to know the overall length and the length from the tail of the bolt rearward. Thanks!

Thanks for the info survivalshop.

No, he's not :)

survivalshop, the centerline of the barrel to the gas tube is the same as an AR15. The issue is that the bolt is larger and the distance from the centerline of the bolt or bore to the gas key is greater on the 308. I'd get the AR10 gas tube, but then I'd be concerned it was too long. I'm guessing. as others have suggested, that's not a major issue. If it was, some company would probably be making an LR308 gas tube by now. I may try to add a little bend to mine when assembling it and see how it feels. I guess if the BCG slides on and off the gas tube smoothly, then it's all good.

The subject of rifle-length gas tubes in 308 builds was recently discussed on another forum. A well-respected gunsmith pointed out that the distance from the bore centerline to the gas key centerline is 1/16" greater on an LR308 than on an AR15. Because of this, the gas tube requires a larger bend (offset) than the standard AR15 gas tube has. According to him, while a standard AR15 gas tube may work, it is not correct and the incorrect fit can lead to future issues. As this site is dedicated to these rifles, I'd like to hear the opinions of those who have a lot of experience with them. I'm working on my first 308 and I'd like it to be setup correctly. I have no problem altering the bend on the gas tube to achieve the additional 1/16" offset. From the info he provided (including the attached drawing), it seems like the additional offset is the right way to build it. The only reason I hesitate is that I've found dozens of posts here saying that an AR15 gas tube is fine to use. Thanks in advance for any info you can provide.