New (to me) Nork... couple of issues!

Silverado

Silverado

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I bought an M305 from the EE a while ago; 22" barrel and a few upgrades - USGI stock, Garand rear sight, etc.

I had it out last night for the first time to see where and how it shoots, and I noticed two issues.

The first is that the rear sight aperture is loose, in spite of tightening the sight screws. I can wiggle it about 1/16" back and forth with my fingers. A quick google search seems to suggest the sight cover is worn; when I press down on it the play goes away. Am I on the right track there?

The second and far more concerning issue is that out of 20 rounds that I fired, I found 6 cases with deeply split necks... 3 were split all the way into the shoulder. I was firing the Norinco copper washed bulk ammo.

I suspect bad headspace here... off to the gunsmith?

TIA for your opinions. Till then I'll degrease the shorty I bought from SFRC and play with that.

Lastly, the 'ping' you all talk about... where is it? I can 'hear' a noise through my cheek when I fire it, very similar to the buffer sound of an AR15... is that it, or would I be hearing it more from the op-rod area?
 
split necks is normaly bad brass/overpresure

buldging shoulders or cracked or visualy stressed case head joining is a head space issue.

of course the chamber diamiter might be off.... the previous owner didn't blow it up did they?
 
Not blown up that I know of! Case heads and bases looked good. The primers aren't pierced or flattened. Shoulders looked normal other than the splitting. Are split necks more common in steel cases?
 
Silverado said:
Not blown up that I know of! Case heads and bases looked good. The primers aren't pierced or flattened. Shoulders looked normal other than the splitting. Are split necks more common in steel cases?
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Depends on how old the case is, what the storage conditions were, and if it was annealed after being made.
 
Silverado said:
Lastly, the 'ping' you all talk about...
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Simple question first. :)

The 'ping' comes from the flash hider, IMO. The bullet exiting the barrel cause a vibration, NOT a strike, and it creates a harmonic that makes the sound. I didn't get the 'ping' at first: the flashhider on mine was spot welded, two underside, and I drilled & smashed it off to shim the gas system. The new flash hider I have pings really well: likely the welds take the ping away.

The "AR buffer" sound you hear could be the gas system: I heard it too before 'Stella got her Ping back'. :p :p :p :p

Silverado said:
The first is that the rear sight aperture is loose, in spite of tightening the sight screws. I can wiggle it about 1/16" back and forth with my fingers. A quick google search seems to suggest the sight cover is worn; when I press down on it the play goes away. Am I on the right track there?
Click to expand...

I had a simliar issue. I ended up finding a "step-by-step sight re-build" photo series (wish I saved the link) on how to troubleshoot and fix problems. If I remember correctly I ended up doing three things: bending the cover, peaning a screw head and putting red Lock-tite on an adjustment nut (bolt and nut needed to turn together, and were not). The sight doesn't move and is good enough for back-up if the scope fails or close shots by looking throught the 'see-through' mount. I didn't want to pay for a Garand sight to only have a functioning sight: I would suggest it if iron sights is all you are going to use.

Silverado said:
The second and far more concerning issue is that out of 20 rounds that I fired, I found 6 cases with deeply split necks... 3 were split all the way into the shoulder. I was firing the Norinco copper washed bulk ammo.

I suspect bad headspace here... off to the gunsmith?
Click to expand...

The tough one last...

It could be a headspace issue. It could be the ammo. I would suggest firing some commercial brass case in the 150-170gr area, something 'snappy' but not overpowered, and inspect the cases very well.

CGN: remind me if someone here is still accepting cases to check for headspace issues? I know I had it done and found my M305 to be 'average'.
 
I'm going to fire a few brass-cased rounds and have a look. After a couple of conversations I think it might be that Chinese ammo.
 
If you have a micrometer or vernier you should measure the diameter of the necks on fired cases and compare that to the neck diameter of a loaded round. The difference is an indication of the diameter of the neck area of the chamber. If the fired cased are .020 bigger than the loaded round - then you have an oversize neck in the rifle.

The chambering operation may not have been done properly which may have caused an oversize neck area. Make no mistake - this IS a dangerous condition. When the case splits, pressure can leak past the brass and blast toward your face. If this happens it will not do your eyes any good.

You can also cobble up a makeshift headspace measuring tool for the brass. All you really need in a block of steel, aluminum or even plastic with a hole in it that contacts the shoulder about half way between the neck and body. The gage needs to be thick enough that you can place a loaded round into it without the bullet pointing out the other end. Anyway - you can use this to measure the brass headspace both before and after firing to determine the amount of case stretch that is occurring. You could also use a length of pipe if the diameter is just right, but it will need to be cut exactly square - a hack saw wont cut it - so to speak.
 
As to the ping... now I get it. My new shorty rings like a struck anvil at every shot. LOL

Also, I suck with iron sights. A little over an inch at 25y is the best I can do. Must practice...
 
I think the ping you are hearing is caused by the operating rod rapping against the receiver at full stroke. I have a nice little rubber bumper that I picked up somewhere that softens that impact. It would be easy for a guy to make even out of a nice piece of leather.

this thing has a hole in it the size of the op rod spring and you just hang it from there just in front of the receiver. It has an ark cut in it to match the barrel profile and it just stays there loosely.

When the gun is fired the op rod hits the rubber bumper and dampens the impact.

It works real good.
 
LordEvilPepper said:
... but in general steel has less elasticity then brass so yeah I could see splitting being a more comman issue
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What do you mean? Elastic limit? Because yes, it's lower for steel than for brass, but it's plenty high enough. Young's modulus? That's higher for steel than brass.



LordEvilPepper said:
if you anneal steel casing... it would harden it and it would crack every time...
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Annealing, by definition, is a thermal process to soften metal. It can't make it harder, or it wouldn't be annealing.
 
Did someone say PING? Have a look at the bottom of page 2 of the FAQ's... In the Glock Blooper vid, the ping happens at 1:43 :D

Back to chamber issue. My USGI M14 rifles ( I owned ALL four of the US Manufacturers AND FOUR M1A's in the past) were always over 15thou chambers. YES, that is larger than a commercial SAAMI NO-GO gauge of 1.638" or 8 thousandths of an inch past the GO gauge of 1.630". My #### is still here (I think). :evil:

Mail me 3 brass cases or 2 and I can measure them to determine a very close chamber dimension.... :D

Cheers,
Barney
 
ActiveShooter said:
Annealing is the opposite of hardening, I bet the manufacturing process work hardens the case and isn't annealed afterwards.
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To geek out a bit...

Assuming the mild (low carbon) steel used in a casing, the affect of annealing will depend on the annealing temperature and the quenching method. High temperature annealing followed by a fast quench will result in a harder metal, than a low temperature annealing and/or a slow quench.

Heating steel causes the metal grains/crystals to grow (the longer the annealing the larger the grains). A high temperature anneal followed by a fast quench could (depending on how hot) result in the grains reforming into a smaller size, hardening the metal. A low temperature anneal over a long time, followed by a fast quench would freeze the large grains, resulting in a softer metal.

Note that the story gets more complicated for higher carbon steels, and even more-so when other alloying materials come into play.

Geek off.
 
steel cased ammo, one use only, split necks no biggie in my opinion

split necks with steel case ammo not rare, I am sure it's usually an ammo issue not rifle issue as I see it across the board in many of my rifles, various calibres, all with no headspace issue, never concerned me at all.
 
Big bear has it right, and I have found the Norinco copper washed ammo somewhat prone to split necks. Headspace in my rifle is 1.638, and I find a few split necks every 20 rounds or so. No big deal, this is surplus ammo after all.
 
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