M305 Bolt Failure

[watermine]

Hi, Has anyone experienced this or heard about it with a M305?

The bolt sheared off at the right hand lug (with the roller) when fired today , took out a tiny chunk of my scalp.

I've fired about 1000 rounds through the rifle with no problems. The load was 150 gr FMJBT, 41.5grains IMR 4064, once fired Federal brass, CCI Primer.

If this is a problem with the bolt, should I just replace it, or could it be something to do with the rest of the rifle?

I called the shop where I purchased this, but they seemed to be more concerned about any warranty claim that I may make, rather than the gun blowing up.

 

[sircastic]

I was just down from you when it happened ... it didn't sound good. Glad to see you were OK later when I was chatting with you in the washroom.

On topic, I'd take it to a gunsmith. After seeing it go boom earlier, I'd be inclined to have a professional inspect / repair it rather than risk having the same type problem again and risk a worse injury.

 

[Rhutch]

I was there, hope you're doing ok. Was it a slam fire or did you pull the trigger and it blew up? What vintage is your Norinco, a new one or have you had it for awhile? I second have sone look at it, might even have the op rod, and receiver MPI'd, to see if there are any cracks. You definitely became the poster boy for eye protection.

 

[watermine]

Thanks, I'm okay. I'm still a little shook up. I had already fired 13 rounds. This happened at the fourth in the mag. I pulled the trigger and that's when the bolt failed. I've had the rifle for just over a year, and apart from this, it's a great rifle, I think its done for now, there is also some chipping on the receiver and the stock is cracked. I haven't disassembled it yet. The rifles serial number indicates that it was built in 2009.

 

[Wildcard91]

I'm glad to hear that you're okay. Definitely have the gun checked out.

Did you find the casing that caused this incident? Have you previously checked to make sure your bolt lugs were engaging properly?

Any pics of the receiver? More details would be great as I'm pretty curious about this incident.

 

[hicaliber]

Actually we were quite concerned that the gun failed and since you had admitted on the phone you were shooting reloads there is no warranty to worry about.All gun manufacturer warranties are voided by shooting reloads.
I'm not sure what exactly you wanted when you called so we suggested you bring it in and let our gunsmith have a look at it but apparently that was not good enough satisfy you.
I'm glad to hear you are ok and might I suggest you take a closer look at your reloads, in these cases this is often the cause of failures.

 

[PorkNBeans]

doh. good thing you're okay. bring it in, get it all fixed up and head back to the range

 

[skip1600]

After 1000 rounds I have my doubts about this being a manufacturers defect. What did the case look like?

 

[wallyj]

Well, here is the thing I see, the rifles are so cheep, perhaps you should buy another one anyway and use this one for parts! Lol...

Anyway, since you are ok we can Joke a bit, but seriously I'm debating buying a second, just cause they are so awesome..

I've only shot a few hundred rounds of milsurp out of mine. I just picked up a can of the federal brass to try, I was getting worried that the primers would be too soft for the semi auto but your handloads may have contributed? Or cheep casting, which way are you leaning..

 

[miykael]

Here's a great resource for loading for the M-14: http://www.zediker.com/downloads/14_loading.pdf

Article writer says 4064 is upper limit for the rifle's gas system too (slow powder and 4895 is probably the best to use). The article explains things really well when it comes to loading for this rifle. The one issue I have is that Norinco's are marked .308 Win, not 7.62x51... is it a mis-marking or is it really .308 Win (which is rated for higher pressure). If it really is 7.62x51, then higher pressure 308Win loads could be creating the problem. Anyone out there know if the Norinco's are marked right - maybe some of you importers/retailers could look into this, as there is a large loading difference between 308Win and 7.62x51 (62K psi vs 50K psi). All imo

Anyway, back on topic. There seems to be a lot of discussion on the net about the bolt's on these rifles. Some say soft bolt issues, others are saying it's the tactic of the replacement bolt makers to slam Chinese bolts. I know that my M305's chamber seems huge compared to my 308 Savage. After so many rounds, maybe it was time for a thorough bolt inspection, disassembly and cleaning?

 

[f55]

Watermine do you have the normal stock that came with the rifle or a boyds?

 

[yomomma]

The one issue i have is that norinco's are marked .308 win, not 7.62x51... Is it a mis-marking or is it really .308 win (which is rated for higher pressure). If it really is 7.62x51, then higher pressure 308win loads could be creating the problem. Anyone out there know if the norinco's are marked right - maybe some of you importers/retailers could look into this, as there is a large loading difference between 308win and 7.62x51 (62k psi vs 50k psi). All imo

wrong.....wrong>>> wrong

the problem with all these arguments, though, is that they're supposition. The data on m80 ball is printed in black and white in tm-43-0001-27, army ammunition data sheets for small caliber ammunition, which flat-out says that 7.62x51mm nato has a maximum pressure of 50,000 psi. This would seem like the final word on the subject, but i believe tm-43-0001-27 is mixing up methods of measuring pressure.

Until sometime in the 1960s, the common method of testing cartridge pressure involved fitting copper plugs into pistons in a test barrel and measuring how much pressure crushed the plug. The measurements produced this way are expressed in copper units of pressure, or cup. It was common practice to use pounds per square inch interchangeably with cup--until piezoelectric transducers started to be used instead of the copper plugs. Piezo pressure measurements are much more accurate than copper crushers, and showed that there is no real relationship between cup and psi (beyond the fact that they both get higher as pressure goes up). Sometimes, they're the same. Most of the time, cup is lower than psi. As a rule, the behavior of copper under pressure is so quirky that there's no reliable way of translating cup to psi mathematically; you just have to measure both ways.

 

[miykael]

What was your point? I mentioned 62K psi vs 50K psi (not psi vs cup, which I know about btw) powder and a bunch of other stuff. You're saying the article writer was wrong about match loading or the chamber pressures for 7.62x51 vs 308Win (SAAMI spec)?

From another post:

.308 Win is loaded to higher pressure than 7.62x51 (but the opposite is true with 5.56x45, as it's higher pressure than 223).

This gives good explanation (just scroll down), I've taken an excerpt: http://www.accurateshooter.com/cartridge-guides/308win/

.308 Win vs. 7.62×51–The Straight Scoop
Before we go much further, we want to address the oft-posed question “Are the .308 Winchester and 7.62×51 NATO one and the same?” The simple answer is no. There are differences in chamber specs and maximum pressures. The SAMMI/CIP maximum pressure for the .308 Win cartridge is 62,000 psi, while the 7.62×51 max is 50,000 psi. Also, the headspace is slightly different. The .308 Win “Go Gauge” is 1.630″ vs. 1.635″ for the 7.62×51. The .308′s “No-Go” dimension is 1.634″ vs. 1.6405″ for a 7.62×51 “No Go” gauge. That said, it is normally fine to shoot quality 7.62×51 NATO ammo in a gun chambered for the .308 Winchester (though not all NATO ammo is identical). Clint McKee of Fulton Armory notes: “[N]obody makes 7.62mm (NATO) ammo that isn’t to the .308 ‘headspace’ dimension spec. So 7.62mm ammo fits nicely into .308 chambers, as a rule.” You CAN encounter problems going the other way, however. A commercial .308 Win round can exceed the max rated pressure for the 7.62×51. So, you should avoid putting full-power .308 Win rounds into military surplus rifles that have been designed for 50,000 psi max. For more information on this interesting topic, read the following articles: Gun Zone’s 30 Caliber FAQ; Cruffler.com Technical Trivia, June 2001; and last, but not least, Steve Redgwell’s .308 vs 7.62×51 Analysis, which really provides a definitive explanation. Reloaders should also note that military ammo often is made with a thicker web. Consequently the case capacity of 7.62×51 brass is usually less than that of commercial .308 brass. You may need to reduce recommended .308 Winchester loads by as much as 2 full grains, if you reload with military 7.62×51 brass, such as Lake City or IMI.

M118 LR and the MilSurp Ammo Option
One reason the .308 Win is so popular is the availability of very inexpensive 7.62×51 military surplus ammo. As explained in more detail above, a 7.62×51 chamber is NOT the same as a SAMMI-spec .308 Win chamber. Nonetheless it is normally safe to shoot 7.62×51 NATO-class ammo in your .308 Win because current .308 Winchester rifles are designed for higher maximum pressures.

wrong.....wrong>>> wrong

 

[yomomma]

Chamber pressures.

 

[watermine]

I've attached another two files showing the damage to the bolt from the side and the reciever.

Until this happened I had no problems with the rifle and I really want to know what happened and if it has ever occurred before. I do plan on replacing this with another M305, but I think I might wait a bit.

Thanks to everyone who has posted



By the way, the rifle had a USGI walnut stock.

 

[Rhutch]

Go to the Federal website, .308 Win is listed as .308 Win (7.62x51mm) so they are labelling their .308 as being 7.62X51 are they mis-marketing or lying?

 

[f55]

View attachment 5606View attachment 5607

I've attached another two files showing the damage to the bolt from the side and the reciever.

Until this happened I had no problems with the rifle and I really want to know what happened and if it has ever occurred before. I do plan on replacing this with another M305, but I think I might wait a bit.

Thanks to everyone who has posted



By the way, the rifle had a USGI walnut stock.

Take a pic of the right side of the stock where the charging handle is and post please.

Did you put the stock on a while ago or recent when this happened?

 

[skip1600]

I think the case will tell more of the story than the bolt.. Too me and I'm no expert it looks like either out of battery or over pressure

 

[beavis_m305]

Perhaps it was only bearing on the right hand bolt lug, and it eventually failed from taking all the force from the firing cycle? yay/nay?

 

[yomomma]

Find me the SAAMI Specs for 7.62x51.....hmmmmm

Oh my gosh, here we go again.......

The psi figures "quoted" are apples and oranges. The 62,000 psi is the current figure for SAAMI based on piezo transducers pressures. The 50,000 psi quoted for the 7.62 NATO is based on the C.U.P. (Copper Unit Pressure) measuring systems. Those are total different and a comparison is totally meaningless.

The actual psi maximum average working pressures (MAPs or PMAPs) for both the 7.62 NATO and the .308W are pretty close to the same; 50,000 C.U.P. or 62,000 psi. The military is now also using a case mouth transducer to measure the psi of 7.62 NATO and 5.56 NATO BTW. I have been measuring the pressure of various lots of US and foreign 7.62 NATO and commercial .308W ammunition in 3 test rifles using an Oehler M43 for several years now. I can show you 7.62 NATO ammunition that is higher that .308W ammunition and visa versa all tested in the same test rifle on the same day under the same conditions. Point is both cartridges are close to the same and it just depends on the specific type and lot of ammunition as to which will have a higher psi. Also don't assume that because the MAP is listed at 62,000 psi that all such ammunition is loaded to that....it isn't. I've yet to find a commercial .308W or a 7.62 NATO MAP that hits that. A couple of each have hit 60,000 psi but most quality .308W/7.62 NATO that meets spec is in the 56 -58,000 psi range. The loading criteria is based on a velocity specification (+/- a lot more fps than you would believe) that stays within SAAMI psi specs (more than just the MAP BTW) and gives adequate "accuracy".

The measured "difference" between the two cartridges is most often in the velocity. The .308W many times will have a higher velocity for a given bullet weight (say 150 vs 147) than the 7.62 NATO. Many assume the higher velocity means a higher psi. That is not the case most often. It means a slower powder was used in the .308W as the time/pressure curves demonstrate. The cartridge case external specifications are the same also. Ever try to buy a set of "7.62 NATO" loading dies? No, probably because they are all .308W dies because the two cartridges are the same externally. Yes milsurp chambers are more generous (need to be to ensure reliable functioning) than commercial .308W but comparing chambers and concluding the cartridges are there for different is an erroneous conclusion.

With bullets of 150 - 165 gr in the .308W there isn't enough of a slower time pressure to harm the M1A/M14. There is just an increase of 75 -100 fps or so velocity. The gas port psi is about the same with those .308W loads as with M118SB or M118LR ammunition.

Newer .308W ammunition of "super performance" or "extended range" have specially blended and much slower powders and should not be used in gas guns. This because of a much slower time/pressure curve that puts too much psi at the gas port. It is not because of increased MAPs in the .308W. Those types of ammunition have MAPs that are like any other .308W commercial ammunition that are within SAAMI specs.

Bottom line is; before going to different sites and cross referencing the "data" one should be aware of how the "data" was obtained. Most often, in the case of .308W vs 7.62 NATO, the "data" was obtained by totally different methods and is meaningless in comparison.

What was your point? I mentioned 62K psi vs 50K psi (not psi vs cup, which I know about btw) powder and a bunch of other stuff. You're saying the article writer was wrong about match loading or the chamber pressures for 7.62x51 vs 308Win (SAAMI spec)?

From another post:

.308 Win is loaded to higher pressure than 7.62x51 (but the opposite is true with 5.56x45, as it's higher pressure than 223).

This gives good explanation (just scroll down), I've taken an excerpt: http://www.accurateshooter.com/cartridge-guides/308win/

.308 Win vs. 7.62×51–The Straight Scoop
Before we go much further, we want to address the oft-posed question “Are the .308 Winchester and 7.62×51 NATO one and the same?” The simple answer is no. There are differences in chamber specs and maximum pressures. The SAMMI/CIP maximum pressure for the .308 Win cartridge is 62,000 psi, while the 7.62×51 max is 50,000 psi. Also, the headspace is slightly different. The .308 Win “Go Gauge” is 1.630″ vs. 1.635″ for the 7.62×51. The .308′s “No-Go” dimension is 1.634″ vs. 1.6405″ for a 7.62×51 “No Go” gauge. That said, it is normally fine to shoot quality 7.62×51 NATO ammo in a gun chambered for the .308 Winchester (though not all NATO ammo is identical). Clint McKee of Fulton Armory notes: “[N]obody makes 7.62mm (NATO) ammo that isn’t to the .308 ‘headspace’ dimension spec. So 7.62mm ammo fits nicely into .308 chambers, as a rule.” You CAN encounter problems going the other way, however. A commercial .308 Win round can exceed the max rated pressure for the 7.62×51. So, you should avoid putting full-power .308 Win rounds into military surplus rifles that have been designed for 50,000 psi max. For more information on this interesting topic, read the following articles: Gun Zone’s 30 Caliber FAQ; Cruffler.com Technical Trivia, June 2001; and last, but not least, Steve Redgwell’s .308 vs 7.62×51 Analysis, which really provides a definitive explanation. Reloaders should also note that military ammo often is made with a thicker web. Consequently the case capacity of 7.62×51 brass is usually less than that of commercial .308 brass. You may need to reduce recommended .308 Winchester loads by as much as 2 full grains, if you reload with military 7.62×51 brass, such as Lake City or IMI.

M118 LR and the MilSurp Ammo Option
One reason the .308 Win is so popular is the availability of very inexpensive 7.62×51 military surplus ammo. As explained in more detail above, a 7.62×51 chamber is NOT the same as a SAMMI-spec .308 Win chamber. Nonetheless it is normally safe to shoot 7.62×51 NATO-class ammo in your .308 Win because current .308 Winchester rifles are designed for higher maximum pressures.