CaveMan

It seems to be working better now. I only had time to put about 9 rounds through it yesterday, but it's working pretty good. It ejects to between 1 and 2 o'clock position now. It seems a lot less "handy" though. I never weighed it with carbine buffer tube and six-position stock, but now it seems almost a pound heavier with A2 stock. I was hoping for a quick and light field rifle in .308 (which may be a pipe dream), but now it seems like it's more of a designated marksman rifle. Eh. At least it's working!

IT'S BACK!!! ...with a rifle length buffer tube and A2 stock. Range report coming soon.

I talked to Brent from CMMG today on the phone, and he is sending me a shipping label to send my rifle back for a second time. He mentioned a few things that he would like to try on the MK-3 rifles, including a smaller gas port on the 18" carbine-length gas systems. He said he didn't have any other barrels in stock to experiment with, but thinks a smaller gas port would help. This jives with the opinions on this forum that the rifle is very over-gassed. The current plan is to send back only the lower. He's going to put a rifle-length buffer tube on it, and an A2 style stock. Hopefully the longer spring / longer buffer will make it work. I am all for this plan, as my friends MK-3 with rifle length buffer works fantastic. I'm OK with the A2 stock, as long as the overall weight of the rifle does not spike. I enjoy how light it is now. Brent also said the change should help mitigate recoil. It has quite the perceived recoil at the moment, from my experience. He said he was happy to pick up the shipping, hopefully they can make this poop work!!!! I will keep you guys posted. <thumbsup>

BayouBob: It seems like it's hitting the buffer squarely. There are no marks on it. Next step, I'm gonna send this thing back. It sucks that they're paying for so much postage, but that's what they get for not fixing it the first time. Anybody have any opinions on DPMS's 308 rifles? Any good? Anything available in 18" medium-profile? Also, apparently I'm quite the whiny bitch when I drink. :) Thanks for reading.

Ok, so I'm going to just rant on here for a second because it's late, and I've had a couple of beers. I'm working a lot of hours these days, as it's the busy season for my industry. I literally work 7 days per week in the marine industry, dealing with really lame clients and trying my damndest to survive in one of the most cutthroat sales jobs I've ever had. It's freaking unreal stressful, and firearms is my one outlet. Shooting guns helps me unwind. I don't have a lot of spare cash. I am on a pretty strict budget, as my wife and I are trying to work our way out of student loan debt. I have limited myself to ONE rifle. I don't have a basement full of guns, or racks and racks of half-finished AR-15s. I literally have ONLY one rifle. The only other rifle in the house is my wife's .308 bolt gun. But we have a deal that it is HER gun, and not mine. I can only shoot it when we go out together. It's not mine, it's hers. A little background: Since 2008, my gun was an FN-FAL. It took 4 months of dedicated savings to buy it. It was my dream gun. And I loved it more than a man should really love an inanimate object. I took care of the FAL. I fed it good ammo. I had a nice sling, a nice case, and lots and lots of magazines. I took it to the range and blasted stuff with it every chance I got. I cleaned it. I showed it off to everybody. It was my prized possession. Again, I'm a "one rifle" kinda guy. Eventually I spent about $500 on a scope for it, and that's when I realized its accuracy limitations. After much thought and agony, I made a hard decision. I sold the FN-FAL. It was like selling my child. I'm not kidding; it was quite emotional. A very nice man, a military firearms collector, purchased my FAL from me for $1200. We met in a parking lot. I watched my dream rifle disappear into the back of his Jeep along with my stack of magazines. I shook his hand, pocketed the cash, and tried to imagine what could POSSIBLY be better than the Right Arm of The Free World. I went from ONE rifle, to ZERO rifles. But I knew my dream was out there. I knew there was an 18" barreled "battle rifle" handy enough to drag through the woods, but accurate enough to hit at 500 yards. I thought, "I can't be the only one who wants a rifle like this. It has to exist!" And with my wad of cash, I started the search. Every review I read of CMMG was positive. Sure, everyone makes a bum gun every once in a while. But that's just life. It's entropy. It's part of the chaos of the gun shopping experience. "Take a chance," my brain said. "They look nice, they're light, and right in your price range." The cash was burning a hole in my pocket. I needed a rifle. And I needed one NOW. I took the MK-3 home with such high hopes. Here I was, finally in the 21st century of battle rifles. Finally, the magazines are being manufactured by modern companies. The ergonomics are the same as current militaries, and all the message board threads about bolt releases, charging handles, etc. applied to me. I had moved into the modern world, with my one rifle. "Yay! Have a beer, CaveMan. You're doing alright," said my brain. That was 2 months ago. And yet, here I am. I'm back to having zero rifles. At best I have half a rifle. I have a gun which jams on every 10th shot. The chaos of the gun shopping experience has fully backfired on me, as CMMG seems unwilling or unable to make me whole again. My one stress reliever, my one fucking hobby, is completely at a standstill. After work, after I feel like the bullpoopy is stacking up to my eyeballs, I can't even go to the range because my rifle is such a piece of crap that it's not even worth mounting my scope. (Yes, that's the $500 scope I purchased for the FN-FAL. It sits gathering dust on the dresser, wishing it had a rifle worthy of it.) So ya see, CMMG, this isn't just a small part of my life. This is very important to me. I really wish you'd see that it's a waste of postage to send rifles back and forth across the Midwest without having been as much as test-fired. I mean, for the $80 that was spent in shipping, I could have bought more ammo. Or more magazines. Or anything. Instead, you paid it to UPS. UPS is the only one prospering here. Please, CMMG. Make this good for me. I guess I have no choice but to send my ONE RIFLE back to you again. I'll politely fill out the technical contact form on your website, and request that my gun be sent back in for service. You'll probably create a UPS label and I'll dutifully pack up my gun in the box again. (Thank God I kept that box. It spends more time in there than in my hands.) And my ONE RIFLE will travel by truck to your shop. *sigh.* Just one request: If you don't know how to fix it, please give me my money back. I know, you technically didn't sell it to me. (You sold it to a distributor who sold it to my local shop.) But poop, if that's your business model, you need to refund my money when it doesn't work. I'll respect you a LOT more if you just say, "CaveMan, we can't fix this thing. It looks pretty, and it's nice and we made it super shiny, but it don't shoot for crap. Here's $1408.74 for your troubles." I would completely understand. No hard feelings, CMMG. ...and I would take that money, and go buy ONE RIFLE from someone else.

UPDATE: I finally got my rifle back from the factory. I took it to the range today after work, where I disassembled it to see the quarter plastic delrin spacer that the factory put in the buffer tube. Not very exciting. According to the repair paperwork, they replaced the broken bolt catch, put a spacer in the buffer tube, and replaced the bolt. I did not have my scope, so I just loaded up three rounds at a time and blasted it a few times. I shot about 15 rounds. The first three rounds ejected, but were still pretty close to me -- about a foot or two from standing. I put some cigarettes on the ground near the brass so you can see where they fell. The rifle's position is close to where it was when in my hands shooting. Eh, at least it's mostly working. Then I shot the second set of three, and this happened on the second shot: This is starting to get ridiculous. Ejection got a little better. A couple of the shots went out as far as 6 feet, which is quite good. Again, Marlboros mark the spot: The jams didn't surprise me much. I mean, what's a little plastic disc going to do in the buffer to change the ejection mechanism? But what was a little strange was how difficult the action was to move. When the bolt closes now, it is really REALLY hard to open. It pretty much takes 2 hands, or some bruised fingers to get the action to open. I have to jerk it to make it release. Here is a video of me showing how difficult it is to pull the charging handle: http://youtu.be/yXyMklebZxs I lubed the heck out of the rifle, cycled it about 50 times, and it was still difficult to move. So I started looking for friction points. According to the paperwork, they replaced the bolt. (The carrier looks the same; there are the same wear marks on the carrier that were there before, I think.) The bolt seems to move with a LOT of friction inside the carrier. I lubed it, but it seems to hang up on a particular point during its travel. The channel inside the carrier seems to be an odd shape which doesn't allow it to move freely. Here is that point, as far as I can tell: I kind of wish they would have left the bolt alone. At least the last bolt moved freely in the carrier so that I could charge the rifle without an inordinate amount of force. Maybe I can tolerate it, if I can work out the jam issue. Near the end of the session, I got another jam. Big surprise. Well, that's where I'm at. It was quite a waste of postage to send this rifle to Missouri and back. It's too bad that it doesn't work; it is the exact weight and features in a .308 rifle that I am looking for. I guess I'll have to trade it in for another brand if I can't make it work. I might still try a heavy buffer. That might help prevent the jams. However, it won't fix how hard it is to use the charging handle. That can probably only be fixed by swapping parts. I'm open to ideas... thanks guys.

Email from Brent at CMMG: Nathan, sorry about the wait. Josh has been out for knee surgery and I've been a one man band going on two weeks, so backed up. I replaced the bolt catch, added the delrin spacer to the back of the spring; which is necessary to prevent the carrier striking the lower/buffer tube on carbines. I'm currently looking into the ejector on the bolt, it seems that our bolts ejectors sit alittle below flush. In my opinion it should be flush and I think this is whats causing the brass to dribble out. FYI don't use steel ammo, it voids the warranty. http://www.cmmginc.com/pages/ammunition.html -- Thanks, Brent B. CMMG, Inc

I just got an email: CMMG is sending out a return label for my rifle. Hopefully they'll get it working.

I TOTALLY should have just snapped his lower on my upper. That's pretty darn basic, I can't believe I didn't think of it. Grr... well, too late now. The bolt latch is busted. I guess as soon as I get the new latch I'm just gonna order a heavy buffer and go from there. I'll keep ya'll updated. I guess I'm glad I have a carbine length buffer tube (assuming I get it working), since one of my goals was a light rifle. I'm trying to keep it under 10lbs. And my friend's rifle is pushing 12 pounds with his heavy barrel and "designated marksman" style stock. But if I need a rifle length buffer for good operation, that's what I'll get. It just seems silly that these were shipped with parts that bang into each other with enough force to dent each other --and it doesn't eject for poop. And nobody noticed?

THE SAGA CONTINUES.... So I went to visit my friend today who has a CMMG MK-3, but a different version. His is having no ejection problems. He has only shot about 40 rounds, but they appear to travel about 9 feet standing, and 6 feet prone. We took our guns apart and started comparing parts. Some interesting differences were noted. First and foremost, I noticed that I am having impact marks on the front of my buffer tube. The bolt is slamming into it making marks on either side. They are highlighted in the above picture. That can't be good!! (Sorry I didn't have my good camera, just a cell phone.) Secondly, his buffer is CONSIDERABLY larger than mine. And it obviously works, since his gun works and mine doesn't. His buffer spring is also longer, and thicker. My friend seems to have the version of the gun that CDNN was selling last year in their catalogue, including a 18" heavy barrel, slotted handguards, Magpul PRS stock, and 2-stage trigger. Here is a comparison of the two lowers: So I thought to myself, "It's time to stop screwing around. Let's try to fix this." Taking Josh from CMMG's advice, I dropped 3 quarters in the buffer tube and re-assembled the gun. I stepped outside to the backyard with 3 rounds in the magazine... The first and second round still demonstrated rather anemic ejection. The third (and last) round did not stay in the ejection port, but fell at my feet. The bolt locked back. ...And the bolt hold open lever promptly broke. WTF??? Well, now I not only need a solution to the ejection problem, I need new parts to even fire the gun. The bottom of the lever snapped right off. I found the small pin in the grass, but couldn't find the broken half of the lever. Not that it would matter, it's broken right in half. [img width=810 height=607]http://i.imgur.com/oig8xl.jpg So that's where I'm at. If CMMG had this rifle working LAST YEAR, why did they change it? Pretty strange. They obviously have a longer buffer tube, a tougher spring, and a much longer buffer on the guns they sold to CDNN. Why mess up a working design? Josh, if you're reading this, you have my mailing address. Please send a new bolt hold open lever and a heavy buffer to me. Alternately, send the buffer system that my buddy has. His seems to work great. In case you didn't notice, I am seriously bummed out. Someone needs to make this right...

So on the way to the gun store this week, I called CMMG. A technician named Josh said he had read this thread. (I sent him a link by their technical support form on the website.) He said that CMMG is working on a solution to it, but indicated that they are aware of the problem with their rifles. He mentioned putting a few quarters in the buffer tube. He also said a heavy buffer might fix it as well. I asked him if they had any heavy buffers laying around that he could send me, and he said he would look. That would be nice-- a company that sends parts needed to make their product work. Josh did not have any specific solutions, although he was very polite. So I went to the gun store, and told the clerk my problem. He had heavy buffers in stock, but they are too long for a .308 gun. (The bolt and carrier are too long). So he opened up the buffer on my gun, took out both the blocks of tungsten that are inside, and put a thin layer of steel shot between them. It's probably only a fraction of an ounce more weight, but it can't hurt. On the way back, Clint from Heavy Buffers called. He explained that I need the CAR-10 buffer and his modified Armalite springs for $125 including shipping. I'll probably order that when I find some cash. He said that CMMG probably uses standard DPMS buffers in their guns, which don't work very well. So I took it to the range. What follows is a pictorial report of shooting German milsurp, Russian steelcase, and Remington Ballistic tip ammo. What a beautiful day to shoot!!! (Well, it was pretty humid, but I just love being at the range.) I'm running this thing WET. Like a swamp. This is the grease I am using. Second shot of the day. German MEN ammo. I guess the steel shot added to the buffer didn't do poop. This is the NEXT round which was partway in the chamber during the jam. The bullet is canted in the case. I threw it away. So I switched to trying some of this Herter's steelcase ammo I have laying around. I got lots of this stuff, and it would great if my rifle ate it. It basically went where I aimed it, which is a good sign. Although there was a random flyer here. So far so good, and no jams. ...but it's STILL leaving the last round in the port, SOMETIMES. The Herters ammo didn't stay tight, though. This is a big-ass crummy group. Suddenly, a big boom and smoke is EVERYWHERE, pouring out of the gun. You should click the link below to see what I am talking about. http://www.youtube.com/watch?v=z4K45cXD6b0 Watch the above video to see smoke leaking out of my magazine and mag well. Definitely a ruptured case head. To be fair, I had this happen one other time with my old rifle, an FN-FAL, with this same ammo. The FAL took it like a champ and kept on chuggin'. This one did the same. It even fed the new round, no problem. The ruptured one went pretty high. But that's within the margin of error for this stuff, anyway. On to some better stuff, the Remington .308 Ballistic Tip ammo has been laying around for a while. We'll see what happens. Didn't group very well, and slid 4 inches to the left. Of course, we couldn't even make this crap make a group with my wife's bolt gun, either. So my standards were low. Don't buy this ammo. I'm still not getting what I would consider "healthy" ejection from the gun. Here are the second to last (on the mat) and last shots with the Remington ammo. 6" ejection seems to be par for the course. I'll let you guys know when I order a heavy buffer, and how it affects the gun. Thanks everyone, for your help so far.

OK, excellent input all around. I'm starting to get a picture of what is happening. ---TOO FAST is the issue, not TOO FAR. ---Adjustable gas block can be unreliable compared to other solutions. ---There is no "proper gas" in 308 ARs with give reliability across ammo like there is in M1As, FALs, AKs, etc. It's simply building an autoloading system that is properly timed with the majority of what you might fire through it. ---There are no .308 gas blocks. Actions: I will be getting a new buffer spring and buffer. Anybody know what weight (5.6 ounce vs. 6.5 ounce) I should get? BTW-- Crap, those are expensive.

Oh, and another theory question: Am I right in thinking the bolt is going TOO FAR back, causing the ejection problems? Why would a bolt be designed to go too far back to allow ejection? That seems like a crummy design, if that's the case. Shouldn't too much gas still allow the darn rifle to eject, albeit with more wear and tear on the parts?

Ok, I think I see how that heavy buffer and spring works. Should I get the 5.6 oz one, or the 6.5 oz one? Doesn't it seem to be addressing the problem of over-gassing with simply a "bigger hammer"? Wouldn't it make more sense to get the correct amount of gas to the gun, rather than letting it bleed everywhere randomly, and stomping the motion down with a heavier spring and buffer? (Sorry for the noobish questions. I've never had an AR before.)

Any suggestion as to what brand of adjustable gas block to purchase? A couple of names that have popped up are PRI and JP Enterprises. JP: PRI: How does it work? Do you adjust with a switch or a screw, or what??