BayouBob

The obvious answer was the adjustable gas block; I was just hoping to get the problem solved on CMMG's nickel rather than mine. Being that I am rather stubborn and since I really do like the rifle I went ahead with a PRI block. 3 and 1/4 turns out and all the brass from 5 different loads ejects briskly and lands in a pile about 6 feet away at 4 o'clock. (I'll disagree about what the brass is doing not being important; it's a symptom of a problem. Kind of like having a good pulse and heart rate so don't worry about the persistent cough.) The recoil impulse seems to be softer as well. Early on I had put a 50 round dose of Tubbs Final Finish through the barrel and even while I was half watching with one eye to see if it was going to stovepipe I got a few 1 inch groups with Federal Gold Medal Match so I think the barrel has real potential for accuracy. Now to start playing with all these boxes of long skinny bullets to see what my old eyes can do with the best handloads. I'll keep reporting and also see what CMMG has to say about my expenses.

You would not believe how violent the action is when this rifle goes off. It feels like it is literally trying to shoot itself apart. (I think it may have already done in the cheap scope I was using to experiment.) My AR's go all the way to 450 Bushmaster and they all run smooth as butter. My bolt guns go all the way to .458 Winchester Mag. so recoil alone isn't what I am feeling. If the adj. gas block can't tame it down then it goes back to CMMG for good. Thanks for the install offer 98; I thought about telling the factory to send me a barrel with the proper gas port when they get some in. I don't have AR 308 specific tools yet but since I like to tinker I'll probably get them to go along with my AR-15 tools.

They finally admitted the gas port was too big for an 18 inch barrel. They told me they didn't have any barrels so they were putting the A2 stock on. (Heavier buffer without paying the price of an H3 buffer.) The rifle ejects everything to 1:00 so the brass is obviously still hitting something on the way out. They are using band-aids instead of fixing the problem. Just because I am in so deep now and I still like the way the rifle looks and feels I've ordered an adjustable gas block. (That was the first advice we got about these rifles but I was hoping the fix would come at CMMG's expense rather than mine.) I'll report back on the results.

I have a call in to a friend in the video business. I'm going to try to get some high speed video of the rifle firing to see exactly what is happening. They have offered a refund and I may yet take them up on it. Of course a refund wouldn't help with the several hundred dollars worth of accessories I bought or the three hundred dollars worth of ammo I have already burned trying to get it right.

Latest fix from CMMG on mine was to remove the carbine stock and tube and put a rifle stock and buffer on it. It ejects but all the brass goes to 1:30. That tells me the brass is still hitting something on the way out.

They know they have a problem with their BCG's. The second thing they did with mine was send a new BCG. They also admit they have too big a gas port drilled in the 18" barrels. The FFT is from a third party. (Midwest I think.) But it may be made to CMMG's specs. Mine was loose enough to rattle and I opened the original shipping box.

The reason that where the brass matters is that it's trajectory is caused by it hitting the inside of the ejection port on the way out. That was what was initially causing all the stovepipes. The heavier buffer and spring has slowed it up just enough to get the brass out but the fact that it is still hitting makes me think that eventually I'll get stovepipes again, probably at the worst possible moment. The working of the action is so violent that I'm afraid the rifle is just going tear itself up. (One of the other posters had his bolt stop break in two.) I'm going to try to take some high speed video of it to observe what is happening in slow motion.

They come with an o-ring on the extractor spring. I tried mine both ways (at the factory's suggestion) I don't think it is an extractor issue. The spring is strong and it is getting a good bite. There is no sign on the rim of the extractor pulling off. They are finally admitting they drilled too big a hole for the gas port. With the A2 stock, buffer and spring there are no stovepipes but all the brass still ejects to 1:30. When I manually eject a loaded round it pops right out at 5:00 like it is supposed to. (Different forces acting on it I know.) Evidently the size and location of the gas port worked fine on their 16" barrels but when the extra 2 inches is added there is just too much gas for the system.

They put an A-2 stock on my Mark 3. It was gone for 2 weeks but that was the only thing they did to it. Brent told me the same thing; they don't have any barrels in stock. I get the impression they don't make their own barrels so all they have are already drilled. I am beginning to wonder if CMMG has gone from a manufacturer to just an assembler of other people's parts. There doesn't seem to be a lot of science in their work. I had just minute to run to the range and put a part of a mag down range. The gun ejected all the rounds but they are still going mostly forward which I don't like. I'll give it one more good trial in a few days and if it isn't right Brent has offered me a refund.

CMMG got my Mark 3 back for the second time last Friday morning. Before I sent back again I asked what the plan was and was told 3 days. It is only 2 days shipping from them to me so I should have had it back today. Don't even have a shipping notification yet so the 3 day part was obviously not true. I am rapidly loosing faith in what by all accounts used to be a reputable company. My phone call Monday will be for a full refund.

Clint, I am new to 308's (have a bunch of AR-15's) and I notice you recomend against flat wire buffer springs. Enlighten a novice. Thanks, Bob

And if the Florida courts don't convict Mr. Zimmerman then Holder and Obama will have the feds charge him with a civil rights violation and if the federal courts don't convict him we'll have free Nike and TV days all over the country!

Caveman, Look at the face of your buffer. Is it getting beat up and gouged by the bolt carrier? Both the buffers I have tried in mine got chewed up by both bolt carriers. It looks on mine like the rear of the bolt carrier isn't hitting the buffer squarely, again telling me that something is out of spec.

It looks like to me they are going to have to go all the way back to their tooling to correct the problem, if they are making their own components. If not they need to get real mean with their supplier. Maybe they are getting their components from Blackthorne or whatever that goober is calling his junk company these days.

Obviously they don't have a clue what is wrong with their rifles. Your results make me feel great; I just sent mine back again today. I tried a heavy buffer and it made no difference. The delrin spacer is to keep the bolt from going so far back in the receiver that the extactor is behind the port when the brass turns loose. They already knew that one spacer isn't enough to do the job when they worked on your rifle. Two emails ago I asked them if they had anybody on their staff that understands the AR system concept. They didn't answer but what they did or didn't do to your rifle seems to be the answer.

That's what I said in my note and my email to them. If it or a new rifle doesn't come back 100% reliable I'll never have any confidence in it. (Or anything else from CMMG after what I have seen with my own eyes the past few weeks.) If they don't make it work and I can figure out how to get a refund I'll have a bunch of mags and accessories to unload. The $300 worth of ammo I've fired off trying to make the thing work will just be chalked up to a bad experience as I don't see them compensating me for my costs.

It is going back to the factory tomorrow. (Again!) I'm not spending any more time or money trying to get a new rifle to work properly. I'm also getting a little weary of techs who while very nice don't seem to have a clue.

Wash, You are right about making the factory do something. Even as patient as I am (and too stubborn to give up) I've about had it. There was a day when I wasn't satisfied with a 1 inch group at 100 meters but my old eyes have reached a point that even with my new catarac lenses 1 inch is about as good as I can do.

Pmags, DPMS Mags, ProMags. Hornady A-Max, Federal 150gr, PMC 147gr, Winchester 150 & 180gr, Federal Gold Medal Match. All perform the same. The factory added a spacer behind the buffer and I added more. The factory sent a new BCG. Brass is still hitting the receiver on the way out. The new BCG stopped the stove pipes but ejection is still weak and forward. Even adding an almost H3 weight buffer has had no effect. On the plus side I've shot some 1 inch groups with both the Federal Gold Medal and the Hornady A-Max.

Before I sent mine back again I decided to put a heavier buffer in it. I cut an H2 steel buffer down to 2 3/4 inches and put in 2 tungsten weights and a lead slug to fill it the rest of the way. That brought the weight up to nearly 5 ounces as opposed to the 3 and 3/4 ounces in the factory buffer. Still just barely rolls the brass out of the receiver and still points it at 1:30. I guess I'll send it back to the factory again but I really don't think anybody at CMMG has a clue what the solution is.

Two inexpensive options to get your scope where you need it are the mini-picatinny risers you can get from several sources including flea-bay for about $15 each or the Millett extra high angle lock rings for about $40. I use the Milletts on my 450 Bushmaster and they are just right and very strong.

I built my finace an AR-15 on a chartreuse Cavalry Arms polymer lower with a matching handguard. The upper is the DPMS Sportical which makes the whole thing really light. Not only is she delighted with it, everybody that sees it thinks it is cool. I wish I could find a Cav. lower in bright red.

New guy has to ask. Is that a falling block .22 semiauto?

My Mark 3 is just like yours and I had the same problem. I sent it back to CMMG and they put a delrin spacer behind the buffer spring. It didn't help at all. (One of the guys on AR-15.com suggested quarters on top of the spacer to keep the BCG from going as far back. I passed that on to Brent and Josh.) That helped but I was still getting the same FTE's on about 1 out of 6 shots. CMMG sent a new BCG and I put 20 rounds of mixed ammo through it today before the storm hit. So far it is working. They told me they had some carriers that were out of spec. It is a lovely rifle and fairly accurate. If it will be reliable it will be great. I'll shoot a bunch more in the next couple of days before declaring the issue fixed. I think the guys at CMMG while very nice, are a little mystified too.