Norinco M4 Last Shot

Here's what you can try ...

Chamber a round from a magazine. Remove the magazine. Fire the round while holding the magazine catch firmly with your finger and see if the bolt locks back after the round is expended.

Check your gas key if it has come loose and that it's lining up precisely with the gas tube and not binding.

See if the gas rings on the bolt are staggered. Or broken.

Look for a broken/chipped extractor.

Adding a D ring, or a proper sized O ring to the extractor spring may solve the issue.

Cycling the bolt by hand, see if you feel any binding throughout the stroke.

Make sure there are no obstructions in the gas tube itself.

Carefully look at the bolt stop to see if any defect can be detected and that it is straight. May be an out spec bolt catch. I've seen plenty of these.

There's always the chance of the gas port being a bit too small from the factory and when it built up some carbon residue, it was enough to cause function issues. This would be the very last thing I'd consider, but very possible.

Check these for now.
 
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There's something else I want to point out that I've run into in the past.

The firing pin retaining pin. This pin is to sit flush with the carrier body, or below, when inserted. You'll note these pins are flattened at the top additionally to the carrier having a recessed hole for it to fit into.

Certain pins I've seen used do not have a flattened head, they are round and will protrudes from the side of the carrier if the hole is not recessed deep enough for the pin to fit flush. The protruding pin will bind against the receiver wall and deter the carrier's travel. Look for a gouge on the inside of the receiver wall.
 
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Publican said:
I am using LAR15 10 round mags in my Norc M4. The bolt does not stay open on the last shot. Is this anything to do with the mags or do I need a tuneup?
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It's definitely not the magazines, and it's definitely the Norc (if that helps point you in the right direction). This has come up with PMAGs, etc. - although apparently it is not prevalent with older PMAGs and EMAGs that used the old Magpul follower design (it has since been updated).
 
easy said:
Here's what you can try ...

Chamber a round from a magazine. Remove the magazine. Fire the round while holding the magazine catch firmly with your finger and see if the bolt locks back after the round is expended.
Click to expand...

Tried this already...bolt holds back every time as long as I hold down the bolt catch.

easy said:
Check your gas key if it has come loose and that it's lining up precisely with the gas tube and not binding.

See if the gas rings on the bolt are staggered. Or broken.

Look for a broken/chipped extractor.

Adding a D ring, or a proper sized O ring to the extractor spring may solve the issue.
Click to expand...

Gas key is tight and lined up, gas rings are intact and staggered, extractor is good.

easy said:
Cycling the bolt by hand, see if you feel any binding throughout the stroke.
Click to expand...

Did this with the lower off, feels fine, lower on, no buffer spring, feels fine.


easy said:
Make sure there are no obstructions in the gas tube itself.

Carefully look at the bolt stop to see if any defect can be detected and that it is straight. May be an out spec bolt catch. I've seen plenty of these.

There's always the chance of the gas port being a bit too small from the factory and when it built up some carbon residue, it was enough to cause function issues. This would be the very last thing I'd consider, but very possible.

Check these for now.
Click to expand...

Honestly, I've checked all the obvious causes of short stroking and I don't think its a cycling/gas issue as the bolt will hold back as long as I hold the bolt catch down when firing.

I was told by someone that my bolt catch could be too low so its not catching the bolt properly?
 
wherermykeys said:
I was told by someone that my bolt catch could be too low so its not catching the bolt properly?
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There's a good chance the hole where the bolt catch spring and plunger sit in has some leftover metal or even anodizing residue that causes more tension on the spring and the magazine spring isn't strong enough to push the follower up to engage the catch and lock the carrier back.

An out of spec bolt catch is also possible and/or a combination of several causes contributing to stacking up to putting distance between the bolt catch and the carrier. How much play is there between the upper and lower receivers? Are you using an Accu-Wedge?
 
Well, when I put a magazine in with the upper off, it pushes the catch up all the way.

No, not using an Accu Wedge and there doesn't seem to be any more play than other ARs...maybe I'll try an o-ring on the front takedown hinge...

Thinking of just throwing in a whole new LPK soon...
 
Just wondering; is it a big deal if the last shot does not hold the bolt open? Like does it mean that the gun is broken or does it affect performance some how?

Sorry I have never used an AR15 before.
 
If your are shooting for speed Ie... if you are doing fast reloads not having it greatly slows you down. Other then that no not really. Although i would be choked if my gun didn't do it as i use it on every reload speedy or not (on my swiss arms tho) just for practice
 
winnipegger said:
If your are shooting for speed Ie... if you are doing fast reloads not having it greatly slows you down. Other then that no not really. Although i would be choked if my gun didn't do it as i use it on every reload speedy or not (on my swiss arms tho) just for practice
Click to expand...

Oh, well that is good to hear as I tend not to rapid fire guns a lot.
 
My buddy has a Norc "M4" and we're putting reloads through it and it only locks back like half of the time. He only has Norc mags though. Shoots like a laser beam though. Impressive rifle, I'm convinced I need one.

If I remember the specs right, we loaded 44.5(I'm going strictly by memory...) grains of BLC2 behind a 55grain FMJ crimped to the cannelure in mixed LC,IVI military brass. We don't have a cronograph yet so we used the lightest .223 loading with BLC2 according to the manual(Lyman) but forgot to reduce the load according to the case differences.
 
I have the same problem with mine. It doesn't lock back after the last round, but if you put the empty mag in and pull the bolt back it will lock back.

I have 1 Pmag and it works fine. So now I have 2 LAR mags and 2 Norico mags that are useless.



JonnyBender
 
i had the same problem with my dlask lower attached to a colt upper.. wouldnt stay open at all.. I tried different types of mags and same problem.. i noticed the catch was only slightly catching the bolt when it was locked.. if i locked the bolt manually, it would slam shut just by shaking the rifle..

i took off the bolt catch, cleaned the hole where the bolt catch spring and plunger go into, with a small drill bit.. didnt make a difference..

I took the latch off again and took a dremmel tool to the part of the latch that contacts the spring and plunger.. I shaved off enough so that when the mag is inserted, there's a .038" of travel measuring from the base of the receiver.. I put it back together and never had a problem with it again..

because your bolt stays open when you hold it, I'm thinking maybe a problem with the latch spring and plunger.. maybe the spring is a little too tight or the latch may be slightly out of spec..

if you want i can bring the grinder on the next range trip.:D
 
Yeah, I think I've narrowed it down to the spring pressure on the bolt catch. I'm going to try taking the spring out and cutting a coil or two off it. I can't see it being anything else at this point. It looks like the catch sticks up pretty far...bring your grinder anyway just in case though :)
 
Since it locked back at first, then stopped, try getting a spray can of clp and spraying it full force into the area around the bolt catch (wear goggles) - you may have a small crud build up in there, that's causing enough friction to slow the catch down.
 
#1bcshooter said:
Are these Marstar M4s that have this problem?
I thought his were better than the others that's why it took so long to get them :rolleyes:
I got mine from the first batch over a yr before they got theirs & havent had any problems :D
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I got mine from the first batch too. I've also not had a problem. I've never used the Norc mags tho.

Not wanting to change the thread but does anyone know the differences?

Mine also doesn't have "Norinco" stamped anywhere on it. - which I kind of like.
 
When I first got my Norinco M4 the bolt wouldnt lock open on the last round either. Luckily Naoh lent me some AR parts to find the problem. First we tried a new buffer spring and buffer from his DPMS..no luck. Then we switched bolt carriers.. still not fixed what it ended up being is my buffer tube was screwed in one thread too far so there was not enough play for the bolt to cycle back far enough for the bolt catch to hold it open. Just that one turn out and it locks open every time. If that doesnt work shave a little bit of material off of the buffer and I bet its fixed. I didnt have to buy any parts or replace anything just a simple adjustment.
 
easy said:
A lot of problems with these Norincos. Westerners must know something about building AR's the Chinese can't figure out while Canadian consumers are used as paying test rats for them.

Are the Chinese magazines at least any good for scrap metal, or would they get flagged at the scrapyard?
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I never used the Norinco mags. I have NHMTG , LAR and Bushmaster all without issues. Remember people when it comes to feeding any firearm the Mag is crucial , why do you think there are million of what people call junk .22semis around. This is why Ruger took care to make sure they got the mag right and presto , firearm that is referenced to when one looks up reliability in the dictionary. For god sakes my No4 all numbers matching superb condition will throw the last round left of bore because apparently the mag musta been dropped and the retainer ears slightly altered . Do i say a No 4 is unreliable because of a damamged(not designed wrong or wrong materials)magazine. People like to waste money for status symbols .Will i'll tell you now ,it dont cut the mustard with me, and no matter how much money you waste on you AR or your blings for it, it won't replace your marksmanship ability.

Merry Christmas all.
 
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