(First post) Ejection problems on MK-3

[Jgun]

I hesitate to comment on this because I'm not sure about the accuracy of all of this. If someone reads it and knows it to be incorrect, please post a correction. I have not done a great deal of experimentation/testing with the other stocks, because all of my .308 AR's (All of my AR's actually) have collapsing carbine type stocks. I'd like to set up one of my guns with the UBR and PRS stocks, just haven't got around to it yet. It has been my understanding that the PRS uses the rifle length buffer tube, and the matching longer buffer as pictured from your friends gun. I have tha Clints CAR buffer, that is, I belive compatible with my shorter buffer tube. Have you considered asking your friend if you could just pin your upper on his lower to function test your gun? And if I were you I'd skip that steel cased ammo, at least until you know you've got a gun that runs. If it cycles on your friends lower, you then know that the problem is in the stock/buffer/spring of your gun.

[Jgun]

Looks like you beat me with that one Drew. Glad my info was accurate.

[CaveMan]

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?

[Jgun]

I would have to agree with you on this, it doesn't make sense to me either, that a company would ship the gun with the wrong combination of parts which prevents  proper function. I have no first hand experience with the CMMG guns, but assuming they are dimensioned similarly to the other DPMS SR 25 pattern guns, there should be no reason why you shouldn't be able to use an AR 15 carbine type buffer tube, CTR or equivilant stock, and one of Clints CAR buffers and matching springs to have a correctly functioning lower.

[CaveMan]

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

[edgecrusher]

that's great, you deserve a break. i think i would still talk to clint though

[CaveMan]

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

[BayouBob]

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.

[survivalshop]

Since the rifles are new & under warranty , just keep sending them back . You have little choice in it , you payed to have a working rifle & they should make it work or give you a new one or your money back.

Now that I said that , it looks like the one that's has the BCG hitting the receiver has some items out of spec.  , bad buffer spring & or to light of buffer ( may have a AR 15 buffer ? ), bbl. gas port incorrect size , ejector hanging up or weak/broken spring , ejector out of spec or the bolt out of spec . & I could keep going .

Switching uppers to try out is a good idea.

I have an older CMMG billet lower & while nice ,it had its share of problems all related to spec's & it will not work with Pmags , steel mags no problems.

First , get some good ammo , no steel case crap , while good for loose chamber older mil spec rifles (like the FN-FAL ) it will cause problems with most precision chambers on the AR 308's , some will work with it but most don't .

I would get good some good ammo & put one round in the mag & see if the the mag will hold open on the last rd. ,if it does , put two or three in & see how it does ejecting & hold open.

Have you tried different mag. manufacturers ?

[BayouBob]

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.

[washguy]

Hiya Bob !    hate to say this ....get rid of that slug one way or another...make the factory take it back the gunstore that sold it to you or sumthin? I hope it was farther than 100 yds for the one inch group...any of my 308's will put one hole thru another at 100

enough is enough....I feel for ya...make it go bye bye :)  Wash

[BayouBob]

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.

[unforgiven]

Hi brother Bob,following this thread brother Wash has got a point.You spent your hard earned money you shouldn't have to fight this rifle so it will work right.Good luck brother,let us know how the factoy is treating this problem.

[washguy]

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.

Know what you mean ....my  implant is in my scope eye...do what I did....get a bigger scope <laughs>  Wash

[survivalshop]

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.

Is the bolt holding back after the last rd. in the mag. , every time ?

What gas block is on the rifle (A2 sight ? )?

When you push in on the ejector , does it push freely with no stopping or hanging up & do you feel it has sufficient spring pressure ( it should be moderately stiff ) ?

Inspect the chamber with a bore light for imperfections , also check the barrel extension & locking lugs for burrs /roughness.

Get a set head space gages or barrow or take to a smith & check head space .( with all three ) 

I would go with Heavy buffers , spring & buffer , Clint's stuff does work . I have not had any problems with DPMS springs & buffers , but others have & HB 's stuff worked for them .

I am using a Superior flat wire spring (Tubbs )in my 16" 308 & it changed the operation of ejection ,not that I had a problem with the stock DPMS set up (I'm still using the std DPMS carbine buffer ) but I wanted to try one & kept it in there because the spent brass falls in one neat pile & I don't have to go all over the range looking for them .

And there's more .

[BayouBob]

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.

[washguy]

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.

Way to go Bob!    Make em give you a new one!

<thumbsup>  Wash

[edgecrusher]

If this doesn't work I'd ask for a full refund.

[BayouBob]

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.

[imschur]

This disappoints me very much as I often buy CMMG stuff because there support has always impressed me. I hope they take proper care of you.

[CaveMan]

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.

[BayouBob]

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.

[washguy]

Hi Guys    after seeing the carrier its the problemo most likely...and you cant cycle it...sooo the cam cant do its thing the way the carrier slot for it is cut...making sense now...cam is fubared due to slot in carrier thus making the bolt fubar and thus making it not eject properly...that weak ejection at the one o clock positon aint even close to what a 308 should do...mine kicks'em way far at the 3oclock to 4o clock position...the delrin spacer is BS...and if you think about it....its trying to make up for out of spec carrier...hell ...maybe the lower is not right either....what do I know though?...I just build my own

Geez fellas... I feel for ya....you gotta believe the folks at the factory should know what the deal is?  they are tooling you around ....the cover up is always worse than the bad deed <dontknow>  Wash

[BayouBob]

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.

[survivalshop]

I agree , there is some thing not right about that BC . It is probably why its hanging up & if its hanging up just pulling it back , its doing it under firing conditions .

Poor metallurgy ?  I would ask for a return postage label & send it right back .