OOPS!!

SuperCub

SuperCub

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Shot some .308 in my 760Carbine this afternoon.

I have used this load before w/no problems at all.

150gr Speer RN, Win primer, 42/3031. All charges are measured on the scale. Brass is twice fired and all the same brand. Extraction was very sticky, but it did come finally. The normal brass is the same batch and load fired just before the failure one.

Not sure what happened :?: :?: :?: :?:

308-2.jpg

308-1.jpg
 
hot load

Looks like a good testament to the strength of the Remington action. Clearly, you ran a very hot load there. Have you double-checked the bullet weight? Made sure the bullet was seated a bit off the rifling? Maybe a bit of oil in the chamber?

Have you pulled some loads to confirm the charge? Were the rest of them OK, or did you stop after this one?

I had a similar thing happen with a 6mm Rem many years ago, but I was throwing powder charges (slow burning "stick" powder) through a powder measure. One of the loads "bridged", with the result that one was tossed light and the next one was too heavy. The result was having to use a 2x4 to open the bolt :shock: I've stuck to ball powders (for powder measure use) since.
 
There is a good chance you are using too much powder for the barrel length you have. Some if the powder is not being used. If you have a chrony,start with about 39 grains and go up in .2 grain increments. You will find that you will get to a point that you will not be gaining velocity, just blowing unused powder out the barrel.

However, by looking at the picture, I don't think that was the cause of this problem.
The primer does not appear to be flattened. Could just be a bad case. How well do you clean your chamber? Do you full length resize?
 
Possible case length issue? If I let my .303's grow they may do that. Not a heavy
load at all.

**Edit... Good Thread! **

--PM
 
Just my observation, but you can see that the other casing in the top pic is ready to go next time. I can see the tell tale white line going around the casing. I think a good part of your problem may be the brass....
 
Not a heavy load at all.
Click to expand...
The load is not too heavy, but he may be blowing unburnt powder out the barrel due to the 18.5 inch length.
I use 39.0 gr. of 3031 with 168's out of a 30 inch barrel for shooting 300 meter ISU matches. The load is very accurate.
 
You have some serious over-pressure signs there with all that brass flow into the extractor cut-out.

It could be over-length cases jambing in the leade and causing pressures to spike.

It could be your loads are really too much for this particular rifle and this case was only the first or the batch to let go. It could also be a single case with an over-load of powder.

It could be you didn't get the bullet fully seated when loading that batch and had it jambed into the leade when you touched it off.

Did you change type or lot number of primers part way through loading this batch? A magnum primer in place of a LR one or a hot primer like a Winchester in place of a CCI could cause pressures to jump abopve what was safe before.

Did a 180 gr RN bullet get mixed into your 150's by accident? (Either on your bench or at the factory. I have had problems with Barnes bullets having odd-balls mixed in with the correct ones.)
 
You have some serious over-pressure signs there with all that brass flow into the extractor cut-out.
Click to expand...

Yep.

Just my observation, but you can see that the other casing in the top pic is ready to go next time. I can see the tell tale white line going around the casing.
Click to expand...

Also yep.


Brass is twice fired and all the same brand.
Click to expand...


Are you using a small base die for your 760? If so you may be setting the shoulder back each time. That may be why you are having short case life.
 
Re: hot load

A-zone said:
Looks like a good testament to the strength of the Remington action.
Click to expand...
There was no indication at all of a rupture at the time of firing. Excellent gas handling in this rifle! :arrow:


A-zone said:
Were the rest of them OK, or did you stop after this one?
Click to expand...
Rest of the loads were OK, before and after. I used this load in two different 760s with no problems at all.....till now :roll: :arrow:


maynard said:
How well do you clean your chamber? Do you full length resize?
Click to expand...
Chamber was clean, besides this was not the 1st round fired from this rifle when it happened. All cases were FL resized. :arrow:


PrairieMedic said:
Possible case length issue?
Click to expand...
I check case length at every loading.


[quote='Boo] It could also be a single case with an over-load of powder.

It could be you didn't get the bullet fully seated when loading that batch and had it jambed into the leade when you touched it off.
[/quote]
I tend to agree that it was either or both in combination of both these causes for pressure increase. :arrow:


[quote='Boo]Did you change type or lot number of primers part way through loading this batch? A magnum primer in place of a LR one or a hot primer like a Winchester in place of a CCI could cause pressures to jump abopve what was safe before.
[/quote]
No change of primer that I am aware of. Maybe a mag primer got in somehow :arrow:


[quote='Boo]
Did a 180 gr RN bullet get mixed into your 150's by accident? (Either on your bench or at the factory. I have had problems with Barnes bullets having odd-balls mixed in with the correct ones.) [/quote]
Bullets were taken from new, unopened boxes. :arrow:


Might never know for sure :!:
 
Re: hot load

SuperCub said:
Bullets were taken from new, unopened boxes. :arrow:
Click to expand...


Twice I have found a few wrong bullets in unopened boxes of Barnes bullets. I found a single 270 bullet in a box of 7mm one time. Never noticed it until it dropped right into a charged case as I was getting ready to seat the bullet. I wonder what would have happened if it had been the other way around?

Another time I found 3 of the blue-coated bullets in a box of standrd flat-base X-Bullets. Even my middle-aged eyes had no problem picking that mistake up though!


SuperCub said:
[Might never know for sure :!:
Click to expand...

Thats the truth! LoL
 
Supercub; Case separations such as you have experienced are the result of sizing your brass a little too short [pushing the shoulder back a bit too much] This can give the overpressure sign as well, but not always. The comment made about the bright "line" just above the web of the case is correct. This is your clue to an imminent case separation, probably on the next firing. Do NOT use this brass again! The load you are using is probably OK, since I have used the same charge in my bolt action 300 Savage, but you need to revisit your die adjustment for this rifle. Size it just enough to get easy chambering, NO MORE!! PM me if you want the procedure to adjust that sizing die to prevent a recurrence of this problem. Eagleye.
 
Eagleye said:
Supercub; Case separations such as you have experienced are the result of sizing your brass a little too short [pushing the shoulder back a bit too much] This can give the overpressure sign as well, but not always. The comment made about the bright "line" just above the web of the case is correct. This is your clue to an imminent case separation, probably on the next firing. Do NOT use this brass again! The load you are using is probably OK, since I have used the same charge in my bolt action 300 Savage, but you need to revisit your die adjustment for this rifle. Size it just enough to get easy chambering, NO MORE!! PM me if you want the procedure to adjust that sizing die to prevent a recurrence of this problem. Eagleye.
Click to expand...
Very good advice here.......

The rifle used here is a Remington 760, so the cases pretty much have to be FL resized, which is normal for the type of rifle. I am able to use the regular dies instead of the small base jobs which does same the brass a bit.

I neck size the brass for the bolts I shoot, but this rifle requires more sizing.

AFAIK, this brass is twice fired. I am going to ditch it and start another batch.

QUESTION.................I wonder about the brass flow into the extractor. Would this happen with the case failure alone, or would high pressures cause this :?: :?:

thnx...........SC
 
I agree with most of the above, brass flow into the extractor is caused only by high pressure.
Examine the other brass fired. Look for a case neck with a chunk out of it. Something that may have lodged in the bore. Freaky thing s happen.
Like the others said, even the OK brass looks like you are right on max for pressure to start with for that gun, wouldn't take much to go over. aybe there was a powder bridge in the funnel of a bit that didn't slide out of the pan from the case you filled before. Weighing each charge is tedious as hell.
 
I haven't figured out what happened. I think the case got an "extra" charge and the excesse pressure caused the head to separate and the brass to flow into the extractor slot.

I weigh every charge on the scale, so the human error could always be at play here.

I have an older Hornady scale here that has been very reliable over the years, with no recent changes.

I weighed the pictured cases and measured for length. Both were pretty much exactly the same, but the one case got alot more pressure than the rest of the batch.

The 760 handled the failure with flying colours. I didn't even realize till I got the case out of the rifle. No gas in the face, debris, nothing 8)

Who knows :?:

SC.................
 
In full length sizing with some die/press combinations, it is possible to set the shoulder back to the extent that the case is no longer head spacing on the shoulder.

It wouldn't hurt to mike your demensions on the resized case.
 
Check your case neck thickness as well....you may have caused enough brass flow on the first firing that the neck is too thick for your chamber....this will cause high pressure with a "normal load" ... ap
 
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