Full Battery Issue

I'm having an problem with my bolt not always going into full battery. When the bolt picks up a round from the magazine (CP 10 rnd), more often than not the bolt does not go into battery. If I retract the bolt and drop the mag, with the round sitting in the chamber the bolt will go into full battery.

Is this an ejector needing to be polished issue? Bullet seating depth? Possible buffer spring issue?

What should I do to run this problem down?

I'm having an problem with my bolt not always going into full battery. When the bolt picks up a round from the magazine (CP 10 rnd), more often than not the bolt does not go into battery. If I retract the bolt and drop the mag, with the round sitting in the chamber the bolt will go into full battery.

Is this an ejector needing to be polished issue? Bullet seating depth? Possible buffer spring issue?

What should I do to run this problem down?

SGT. J:

OK -- critical thinking now.

With the magazine removed from the equation, the bolt chambers the cartridge perfectly every time. When the magazine is inserted into the equation, the bolt won't chamber a cartridge most of the time.

So, what do you think the problem is?

You may want to take a look at the Magazine 101 Sticky.

LR1955

Doh! Yeah I suppose so. Thanks for the sarcastic answer so I can see what should have been obvious. I just assumed CP had the mag thing down by now.

Even 5.56 issue mags can be a problem if dropped or just not right.

So after reading the entire magazine 101 thread, I am still not clear. I am not at home where I can tweak my mag lips and test it. But it seems that people having feed issues are seeing problems with the round binding and not allowing the bolt to chamber the round. What I am seeing is that the round chambers but the bolt doesnt fully seat with the lugs. I see about a 1/4" gap where the front of the BCG hasnt fully slid home. Would this mean the BCG is dragging on the top of the lips? Do I need a stronger buffer spring? I still dont see how bending the lips will solve this issue.

Doh! Yeah I suppose so. Thanks for the sarcastic answer so I can see what should have been obvious. I just assumed CP had the mag thing down by now.

SGT. J:

Well, you took it well. If I really intended on being sarcastic I would have said something like 'Duhhh....' but your question reminded me of Joes too much to let it go.

I have had the same problem and others here as well. I just can't remember the thread. This stuff happens for different reasons or a combination. In my case, it was the CP magazine. I can't remember what I did but CP will take back magazines no questions asked and replace them -- with magazines that are still poorly designed and made.

I bet that when this seemingly Grendel unique jam occurs (never had it happen with any other cartridge / gas gun combination) that if you drew the charging handle back a inch and let it go, the round would chamber.

The round is heading into the barrel at too radical an angle most likely and so guys tweak the magazines so the magazine will actually feed reliably.

Welcome to the world of CP Grendel magazines!

LR1955

So I'll keep one of the two to try tweaking, send the other back and maybe by some more that will hopefully yeild at least one that feeds reliably.

Sarge If the rifle is brand new sometimes they run a little stiff before everything gets seated in. Lube it well and cycle the action to get it to loosen up. I hear that some people find certain bullets mostly soft points sometimes get hung up on the feed ramps. Is it factory ammo or reloads? If the bullets are seated out too far they can stop the rifle from going into battery(and cause high pressure too) and subsequent cycling will force the bullet either into the lands or to seat deaper in the case. Just a few more ideas.

Had the same problem here. This is what I did:
Polished feed ramps to knock off the sharp edges
Installed Wolff extra power buffer spring
Installed DPMS Accurising Wedge
Tweaked ever so slightly the mags front (to eliminate rocking) and feed lips

Now it has ran 100% for over 300 rounds. Using a stock DPMS A2 buffer.

load 8rds. in the mag. and see if the rifle will charge.

Looks like the feed issue was that there was too much pressure from the extractor. The bolt came with a defender-like ring around the extractor spring. I took that off and so far hand-cycling rounds through the mags, it feeds 100%. Have to range test it still. I did notice that my bullets are sliding out of the case neck when chambered. I dont have a crimp die so it's either get the Lee FCD or get the Redding bushing neck die. Man... it never stops does it?

Sarge the Lee FCD is not going to help the loads that are loose. They need to be tight to begin with. Are you using Wolf brass? They tend to have thin necks. It would be a shame to buy a new set of dies or die only to find out nothing changed, however the Redding full length bushing die can be purshased separately. http://www.midwayusa.com/viewProduct/?productNumber=754248 Again I would check the size of your expander button and see if it is out of spec.

I have 200 Hornady cases, and 100 Winchester 7.62x39mm (have yet to be fired) cases. What is the spec for the expander? With the Type S FL sizer, I read on the Redding web site they recommend a .001" - .002" neck down from the measurement of the loaded round. But I believe that is for a bolt rifle. I am guessing .002" - .003" for a gas gun. Would this be correct?

I have 200 Hornady cases, and 100 Winchester 7.62x39mm (have yet to be fired) cases. What is the spec for the expander? With the Type S FL sizer, I read on the Redding web site they recommend a .001" - .002" neck down from the measurement of the loaded round. But I believe that is for a bolt rifle. I am guessing .002" - .003" for a gas gun. Would this be correct?

SGT J:

Get rid of the Lee crap.

Get a Redding bushing sizing die and three sizes of bushings. .284, .286, and .288. For the Wolf brass, use the .284. For the 7.62 X 30 and Lapua / AA and Hornday brass use the .286 but some guys use the .288 bushing too.

Problem solved.

LR1955

Roger that.

I just measured the neck OD for both the Hornday and the 7.62x39 brass and they are both .288" loaded. Subtract the .003" and I'm looking at a bushing of .285". Or should I be subtracting .002"? What is the proper tension for a gas gun?

Roger that.

I just measured the neck OD for both the Hornday and the 7.62x39 brass and they are both .288" loaded. Subtract the .003" and I'm looking at a bushing of .285". Or should I be subtracting .002"? What is the proper tension for a gas gun?

SGT J:

OK, get a .285 then.

However, I think you can trust me and others here when we recommend .284, .286, and .288. I am sure Redding can custom make one for you at .285 but your measuring instrument may just call it .284 or .286. You are talking .001" here and that is getting into the realm of insignificant given a gas gun that is designed for service use.

How do I and others know the right neck tension? We base it on how much resistance we get when seating bullets into the sized necks. Some guys like a lot and others not as much but none of us like too little.

OK, here is how you can check. Size a piece of brass using the .284 and another one using the .286 and then the .288. Seat them noting how much resistance you got. Take my word for it, you will know if the neck tension is insufficient or too much just from this action. But, if you are still not sure, here is what you can do.

Try to push the bullets into the cases by hand or put the tips on a piece of wood and try to push them into the case using slight force. My bets are that the one using the .288 bushing will end up pushed into the case.

If still not sure, look at the cases from the side and you will probably see that the case using the .284 bushing is bulged due to the bullet basically expanding the neck because it was sized down too much. That is OK but probably not so great for accuracy purposes.

If you are still not sure, measure the OAL of each then chamber them by drawing the charging handle back all the way and letting the bolt slam home stripping the dummy cartridge from the magazine in the process. Then measure again. The ones that do not get pushed into the case in the process more than about .002" are OK.

There you go. Use common sense with this whole thing and you will be fine.

LR1955

Do you have rifling marks on your bullets? They might just be seated too long for the new bbl. Its happened to many of us. When you are ejecting by hand, the bullet pulls from being too far in the throat etc.

Great info guys! I did go with the 284 286 and 288 bushings. I think the UPS guy is going to wear grooves in the asphalt outside my place!

I will check my jackets for grooves but I dont think there were any.

Great info guys! I did go with the 284 286 and 288 bushings. I think the UPS guy is going to wear grooves in the asphalt outside my place!

I will check my jackets for grooves but I dont think there were any.

With the compound throat on that chamber, you might not see rifling marks. It could just be grabbing the bullket. You can be sure by seating a couple of bullets deeper using your die set as is. If it stops by seating .020" or so deeper, its the chamber/throat grabbing the bullet. Do you have an enertia/hammer type bullet puller? If so, see how much of a hit it takes to move the bullet forward as your dies are now. If it takes some pretty hard whacks, I doubt its neck tension causing it.