kazuaki

Could it be one of these? http://www.davidtubb.com/ar15-tubb-parts/carrierweight-ar15

dbwalker, I recently completed a Juggernaut 308 80% lower. I ended up making spacers similar to what you did in order to avoid the bowing of the jig. I didn't have any issues with the hardness of their material, but I did run into a few other problems with their lower. First off, the buffer retainer hole (which is already drilled by Juggernaut) is too far to the rear of the lower. This results in the buffer sitting perfectly flush with the lower, instead of protruding a bit like it is supposed to. This led to the buffer slamming into the retainer during firing and may have contributed to some of the malfunctions I was experiencing. My solution was to fill the hole with JB Weld and mill a new hole slightly forward of the original. Your lower may or may not have this issue. Second, when using their jig to locate the trigger and hammer pin holes, I ended up with my Wilson Combat TTU hammer making contact with the bolt catch at the same time that it would contact the firing pin. If I dry fired the weapon, the bolt catch would be impact and bind up. This was taking away from the strength of the hammer strike. I have since found that the shape of the hammer plays a big part in this. While my Wilson had the issue, my Geissele does not. Just something to look out for. BTW, I'm using the Juggernaut upper as well. You can find more info about my saga here, or you can PM me if you have any specific questions.

So, I picked up a Black Hole Weaponry 20" barrel (polygonal rifling) during the 20% off sale they are having. I put that in and took a trip to the range today. This barrel seems to be a real shooter. Here's my best 5 shot group of the day. This was done at 100 yards with Federal Gold Medal Match 175gr factory ammo.

So, the range trip went well. I shot about 20 rounds of 147gr ammo, cleaning after every 5 rounds as a quick break-in. I then shot a bunch of Federal Gold Medal and some of the Eagle Eye that gave me issues before. I'm happy to report there were no malfunctions and no pierced primers. I think the rifle has great accuracy potential, but I need a lot of practice/training to become consistent. My best group is below. As you can see from the two sets of measurements, I had a great group going through 4 shots (0.56 MOA), then I pulled the 5th shot and it opened up to 1.07 MOA. Like I said, the rifle shows potential, but I need some work. BTW, I was shooting from a bipod with a rear bag on a wooden bench. Thanks to all for the help this far!

Yeah, I've done about 10 AR-15 80% lowers and all were great. This Juggernaut 308 just wasn't...

Wash, when my rifle was fully assembled, and dry firing (or live firing) the hammer would strike the bolt catch at the same time or slightly before it bottomed on the firing pin. That is not correct. That should never happen. The hammer contacting the bolt catch during operation is taking power away from the firing pin strike. There were two root causes to this. First, this Juggernaut Tactical lower has been a crap investment. The fire control group is slightly too close to the bolt catch. I have verified over and over again that my pin holes line up exactly with their jig. When comparing to drawings if other LR308 lowers I've found, the space from bolt catch to hammer pin is slightly less in mine. Second, the profile of the hammer on the Wilson Combat TTU I was using may have slightly contributed to it. Although a standard milspec hammer I had looked like it had the same profile. Just to be clear, my hammer did not contact the lower, only the bolt catch. I verified this by marking the parts with ink and then watching where the ink was rubbed off.

I ended up ordering (and just received) the DMR. I also ordered a set of the Match springs from Geissele after confirming that was the only difference between the two models.

So, the replacement Mega barrel showed up, as did the Rubber City Armory high pressure bolt. I assembled the upper and checked headspace, all is good. I had disassembled the lower to fix my buffer retainer issue. Somehow while reassembling the lower, a Geissele Hi-Speed Match trigger showed up in there ::). This forum is already costing me money... Anyway, when I put the upper onto the lower, the buffer is slightly pressed off of the retainer, as it should be. The trigger hammer does not make contact with the bolt catch. I believe I've addressed all the issues up to this point. I'm planning a quick trip to the range Sunday morning. Hopefully I've got a reliable and accurate rifle now :unsure:

I see :) All that being said, I felt like the BCM design (and maybe others I haven't tried) was a genuine improvement. Especially if you have optics mounted.

I really like the BCM Gunfighter handle I use. What is the benefit of these newer designs?

Got confirmation from Geissele that the springs can be changed to swap from DMR to Match. Now I just need to find a deal on either of those triggers, then order the spare springs for the other.

Are you using it towards the lighter end if the adjustment? Does anybody know if the only diff between the DMR and the Match is the springs? If so, I could just buy spare spring and essentially have both triggers. I asked Geissele that question, but not gotten a response yet.

Latest update: new Mega barrel will be here tomorrow. Rubber City Armory high pressure bolt (not the whole BCG) is on the way as well. Once I get those parts and reassemble, we'll see where I am.

I've got the Wilson Combat TTU 2 stage right now. It's a very nice drop in non adjustable unit. Really good trigger, but not as light as I'd like (about 4 pounds total). I'm using it since I had it already, from a previous AR15 build.

Any opinions on the match version of the high speed (part 05-127). My understanding is its just a lighter version of the DMR. I know its adjustable, just like the DMR, but probably uses a lighter spring. Any downside on a LR308 setup for longer range shooting from a bench or prone? Will the lighter pull give any additional benefits over the DMR? Thanks

Not yet. I've been trying to get Rubber City Armory to take my money (they were recommended by Mega), but their website isn't accepting orders and I haven't gotten a call back from them yet.

Got notification from Mega that my new barrel is shipping out to me today. Top notch service...

Well, that part worked out. Let's see how the pierced primer issue works out.

The hole was moved forward a total of .040", so there's not a bunch of the JB Weld left in there.

Well, one problem solved :) I filled the buffer retainer hole with JB Weld, let it set, then milled a new hole where Juggernaut should have put it in the first place. Used a 1/4" center cutting endmill in the mill to make a nice perfect hole at a 6 degree angle.

Agreed. I'm not suggesting the bolt or barrel is the cause of my issues, but the fact that I can close the bolt on a NOGO gauge is less than ideal. They gave me some measurements to check on the bolt and it seems to check out. So they said, just ship it back and we'll swap it. Very happy with that service. They also recommended Rubber City Armory bolts to me. Apparently they use the smaller firing pin design (like the JP high pressure bolt) to better handle high pressure loads. I may look into that, especially since my bolt has now had a dozen or more metal discs shoved through the firing pin hole.

I've been in touch with Mega today and they have offered to replace the barrel, no problem, as a precaution. I may take them up on that. They sent me some measurements for the 308 bolt and mine appears to be within spec.

I'm thinking I checked headspace incorrectly originally. I used the bolt by itself and tried to rotate it closed in the chamber by hand. I just rechecked with the bolt in the carrier (still no ejector), so that the carrier would do the work of rotating the bolt. With a gentle press on the back of the BCG, I can get it to close on a NO-GO guage. I've got so many problems :( BTW, the BCG is from AIM Surplus and the barrel is from Mega.

Yes, I actually have new Forster gauges (GO, NOGO, and FIELD) and I checked all three. The ejector was removed first.

Survivalshop, Eagle Eye Ammo: http://www.eagleeyeammo.com/308-win-175gr-hpbt/ Regarding the buffer, there is absolutely zero contact between the BCG and buffer when closing the rifle. Clearly, that is an issue. It seems we've narrowed that issue down to the lower not being correct. The buffer retainer hole is not to spec. I'm weighing my options on resolving that issue still. With regards to the pierced primers, I had one round of Federal Gold Medal Match that was pierced as well. Not sure what's up with that. Until yesterday, when I started searching for explanations to all this, I did not realize that a semi auto needed a slightly milder load than a bolt gun. I've read a few things stating that some Ammo might just be too hot a load for the semi auto. I don't exactly understand why or the details of that. I know JP states that their High Pressure bolt was created to address issues with hot loads in these guns. BTW, yes the headspace was checked with both a GO and NO-GO gauge before the trip to the range.