M305 and Pierced Primers

gnmontey

gnmontey

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First trip to the range with my M305.

After 4 rounds of Chinese ball ammo (loaded one at a time from the mag) the rifle failed to cycle and it took considerable force to open then action. Once the spent casing was ejected a pierced primer was discovered.

Changed to South African ball ammo. Same as above, only the fault occured on shooting round #3.

One more try. After firing 2 SA rounds the rifle failed to cycle and the action was impossible to open with out assistance from a BFH (which I didn't have with me).

Aborted range trip (1 hours travel time) and went home to analyze problem.

Is this a rifle issue or an ammo issue?

I hope I don't offend any one with this post! I'm perplexed. For ball ammo the spent primers are abnormally flat in my opinion (I reload).

Montey
 
This is pretty much standard with some M305 as mine does it to. It only happens with Surplus ammo. I have yet to pierce a store bought or handload with the same rifle. As near as I can figure the firing pin just protrudes to far.
 
Don't feel that you offended anyone. This is what forums like this are for.Pool our knowledge and try and find the solution if someone feels offended,too stinking bad.They can go play some where else.OK rant over.
 
With regards to cleaning....

Upon receiving the rifle from MarStar, I soaked all of the metal parts in gasoline for 4 hours and then gave them a brushing.

The next day, I gave everything a light oiling.

There after, I reassembled the rifle and gave the bore and chamber a good bronze brush cleaning treatment.

Prior to the range run, I greased all of the moving parts.

As an FYI, the round that locked the action did not have a peirced primer?

I can live with the peirced primers (Maybe????). It's the locked up action, I don't want to deal with.

Montey
 
What did the extracted brass look like. Did you notice anything wrong with the brass other than the primers. Is your gas valve in the full open position and not plugged. Do you feel anything binding when you cycle the action or any rough spots. More info would help or possibly some pictures. PS if you can't find the problem contact Marstar and they will fix it.
 
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OK, first things first .... the chinese bolts have slightly larger firing pin holes than the US GI bolts. The firing pin hole on every Chinese bolt I've checked measures greater than what US GI calls for as the maximum.

When you consider that the GI and Chinese firing pins are not as different in tip diameter dimension, it is obvious that some Chinese bolts may have generous clearances here.

OOPS!!
[;{(
Too much clearance between the firing pin tip and the fring pin hole in the bolt can cause bits of brass to flake off into the hole.
BTDT.
Flakes of brass in the firing pin hole can cause the firing pin to jam in the forward position,
which is definitely NOT A GOOD THING!!

We won't even go into firing pin length, protrusion, and bolt/firing pin/receiver bridge timing here, as I would not diagnose these things without the gun in my hands.

Good luck with that ....
and just so you don't feel alone,
my personal, hand built, best parts I can find, shorty M-14 just started to jam last range session. After about 7 or 8 dozen of these rifles through my hands, all of them usually TOTALLY reliable, the one I build for myself to keep is giving me grief.

Oh well,
I suspect a beat up buffer, or else the new after market HD hammer spring, or else I guess I really should clean my guns more than once a year, whether they need it or not.
LAZ 1
 
I just discovered that the Ball ammo I was using has Berdan primers. Is this good, bad or shouldn't matter? I would assume it shouldn't matter. What does the US Mil issue?

After cleaning the rifle, I dry fired a couple of spent factory 308 casings. The rifle does produce a pronounced primer dimple. More pronounced than my bolt 308.

The interesting part is that the first 2-3 rounds fired produced what I would consider to be a normal primer dimple, then, wham, a pierced primer and a locked action.

What now? Trash 400 rounds of Ball ammo and start reloading?
 
Berdan primers is not what is causing this. You have something wrong at the bolt end...just have to isolate what it is. Have you disassembed the bolt? I had hard grit like cosmoline in the bolt on one of my Norincos. That might be part of the problem....

Where did you get the rifle from?

Cheers

Jeff
 
The Norc was purchased new from Marstar in Nov 07. I have not taken the bolt apart and was hoping to avoid that procedure.
 
There are those who will argue there is no such thing as a pierced primer... the firing pin does not pierce the primer... the primer blows out because of a poor fit of the firing pin in the firing pin hole and/or a weak firing pin.

You say you discovered a pierced primer... what did it look like?

Did a small disc blow out completely or partially?

Try different ammo, if it works better, blame the cheap ammo... if it fails with all makes blame the cheap rifle.
 
gnmontey said:
I will provide images if you can explain to me how one inserts an image into this post
Click to expand...

You have to have the image stored on a website first.. preferably a picture no larger than 600 x 800 pixels. (480 x 640 is good) Then while viewing that picture on that website, copy the address from the address bar.

Click on the link above a square box [highlights "insert image" when cursor in placed on it] and paste the address.

Your picture should appear.
 
Lazerus2000 beat me to it. I recommend stripping your bolt, and checking for bits of metal in the firing pin channel. If primer metal is extruding into the channel, it usually indicates excessive clearance between the firing pin protrusion and the hole in the bolt-face, sometimes combined with a mis-shaped firing pin tip (rough edge, etc.). I have found the easiest way to correct this problem is to install a USGI firing pin.
 
This is the Norc ammo
Norc762Nato.JPG


This is the SA ammo
SA762Nato.JPG


I can blow air through the ones with the black holes!

AND...... I take back the part about living with pierced primers.
 
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2nd trip to the range today.

I fired 30 rounds of Federal 150gr factory ammo and had no primer issues. Managed to obtain a 1" four shot group @ 100m benched (not bad for a $400 rifle).

Next, I fired 15 rounds of the Norc ball ammo and had no primer issues????

The one and only round of SA ball ammo fired, locked the action. The primer was not pierced, but I had to use a BFH to open the action.

Why would a pierced primer issue simply vanish?
 
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3rd trip to the range.

Fired Norc Ball, SA Ball, Fed 150 Factory, and walked through a test load of Win 748 (43.5-48.0 gr ), Win Brass, 150 Gr Horn SP, CCI WLR primer. Nothing broke, NO PIERCED PRIMERS, NO LOCKED ACTION, and the short stroking issue has ceased. All is well.

It's a pretty cool piece when it behaves properly!
 
Funny as it might sound, you are breaking in the rifle. Although overtravel is not what I'd expect, the two troublefree range trips are a sign whatever wasn't working has settled into its proper place. Monitor for a while, then if it goes away don't worry. But, knowing this rifle has pierced primers always wear more eye protection than you might normally.

Check the slot on the gas cutoff screw on the side of the gas cylinder. If it is square up (or sideways, forget which) not slanted, the short stroking shouldn't be a concern.
 
I fired off 40 rounds of IVI 77 milsurp ammo last night and had 1/40 result in a pierced primer. Smoke coming out of the action, but no malfunctions aside from one casing caught between the bolt and the smith enterprises scope mount. You are getting some pretty good groupings there. Best 5 shot group I could get at 100 yards with that ammo was 2". Often there would be one wild one that was 4-6" off center of the others. The ammo used seems to really make a difference on my guns for both function and accuracy.
 
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