Case stuck in chamber, primer leaked at edge

[jelenko]

I think this is the result of too much pressure, but wanted to confirm.
This is with an AR15. Load is 26.0 BLC2, S69's loaded to 2.290, Win 41 primer. Muzzle velocity is just over 2900.
Round fired, bolt carrier locked back - case stuck in chamber - but primer doesn't look particularly flat. Lots of smoke came out of the upper after the round was fired. There is some rim missing where the extractor ripped it off.
There is a ~ 25 thousandth hole at the edge of the primer.

To get the stuck case case out, I had to lightly tap a cleaning rod that was inserted through the muzzle. The case did not come out when I first tried hitting the cleaning rod with my palm.

Using a mic, this case head appears to be 7-9 10 thousandths larger than other cases fired in the same chamber.

At first I was focused on the hole at the edge of the primer thinking it's the 'known' issue with Winchester primers. But, the case being stuck seems to say it must have been high pressure, yes?

 

[jds holler]

The Hodgdon Site shows 26 BLC as max with 55's. Also some folks have found that powder to be spicy with high temperature.

It's one of my favorites, but I don't hit the upper end with it. jd

 

[gunsandgunsmithing]

I think this is the result of too much pressure, but wanted to confirm.
This is with an AR15. Load is 26.0 BLC2, S69's loaded to 2.290, Win 41 primer. Muzzle velocity is just over 2900.
Round fired, bolt carrier locked back - case stuck in chamber - but primer doesn't look particularly flat. Lots of smoke came out of the upper after the round was fired. There is some rim missing where the extractor ripped it off.
There is a ~ 25 thousandth hole at the edge of the primer.

To get the stuck case case out, I had to lightly tap a cleaning rod that was inserted through the muzzle. The case did not come out when I first tried hitting the cleaning rod with my palm.

Using a mic, this case head appears to be 7-9 thousandths larger than other cases fired in the same chamber.

At first I was focused on the hole at the edge of the primer thinking it's the 'known' issue with Winchester primers. But, the case being stuck seems to say it must have been high pressure, yes?

Looks and sounds like pressure to me. Can't tell but looks like the primer is "welded" into a stretched out primer pocket and there's a significant ejector mark on the case as well. And yeah, if it's .007-.009 bigger than the other fired cases, that's another sure sign that something went wrong here. Almost certainly excess pressure IMO.

 

[jds holler]

OOPS, I looked again, and I see that powder listed with 26.5 gr. and 69Gr HPBT's. jd

 

[jelenko]

Yeah. So, I'm freaking out.
Have a match tomorrow and have no idea of what caused the pressure. I'm assuming that somehow more powder got into that case, but I'm loading on a Dillon. BLC2 being a ball powder 'should' be pretty consistent.

I guess I'd better load some more rounds weighing each charge.

But, at least it looks like I don't have the Winchester leaking at the edge issue. I.e., this leak was caused by high pressure.

 

[jelenko]

OOPS, I looked again, and I see that powder listed with 26.5 gr. and 69Gr HPBT's. jd

Thanks for checking.
I had used GRT in load development. 8 rounds chronoed at 2896 with ~ 47K psi.

 

[762willdo]

“Should be” has no place in reloading……….or brain surgery………..

 

[B23]

Curious, are you actually chronographing every shot and that's how you know this particular round was "just over 2900" or is it that you've shot this exact load in this rifle before and you got just over 2900 so you're assuming this one was the same? I'm asking because everything indicates extreme high pressure but with a round that had high pressure you also should have seen a pretty significant jump in velocity as well.

Running your exact load through QL using a case capacity of 30gr H2O which depending on your specific brass, looks like you're using Wolf, and not knowing you barrel length I guessed and put in 20in. it shows your load being 2866FPS at 51,899 PSI which is less then SAAMI's max of 55,000. Knowing your actual barrel length would be helpful but if it's somewhere in the 20-22in. length just over 2900fps is within a reasonable range you'd expect from this combo. For comparison a 22in shows 2930 where as a 18in was 2794. It could be that gas leaking out around the primer instead of driving the bullet forward out the muzzle caused the velocity to be lower than you'd expect from a high pressure round but that's all assuming this actual round was chronographed and not just assumed based off a prior same load.

IMO, a chronograph, to a degree, can act like your pressure gauge.

Was this piece of brass new or had it been shot before and do you recall how tight the primer went in? Are you loading those 69's very close to touching the lands? If you're OAL is one that puts them fairly close to touching and you have one that slips by and OAL is at touch or maybe even slightly in to the lands by a thou or two it can spike up the pressure in a hurry and take a safe load to well over max. Lots of variables can cause increased pressure, some, more significant than others but if you have a couple smaller pressure increasing variables stack up on you they can equal a big variable.

 

[K22]

Using a mic, this case head appears to be 7-9 thousandths larger than other cases fired in the same chamber.

If your measurements are correct*, this is a sure sign of excessive pressure, potentially dangerous.

*using a ball or knife edge micrometer.

One of the characteristics of ball powder in my experience is that slight changes in charge can produce large changes in pressure. Extruded powder is more forgiving in this regard. Elevated temperatures exacerbate the issue.

 

[jelenko]

Looks and sounds like pressure to me. Can't tell but looks like the primer is "welded" into a stretched out primer pocket and there's a significant ejector mark on the case as well. And yeah, if it's .007-.009 bigger than the other fired cases, that's another sure sign that something went wrong here. Almost certainly excess pressure IMO.

Maybe you assumed, but the case is 7-9 10ths larger than other cases fired in the same chamber. 7-9 thousandths is probably way beyond the diameter of the chamber.

 

[jelenko]

If your measurements are correct*

Well, duh, it's 7-9 tenths, not whole thousandths.
The mic I have has flat end - but I'm thinking that 7-9 tenths is enough to say that the case is significantly larger than the other fired cases, yes?

 

[gunsandgunsmithing]

Maybe you assumed, but the case is 7-9 10ths larger than other cases fired in the same chamber. 7-9 thousandths is probably way beyond the diameter of the chamber.

Yes but as you said, 7-9 tenths is too much also. .0007-.0009. As far as I'm concerned the actual number was immaterial to the problem. It's the internet, where ya gotta read between the lines at times rather than constantly question every detail in type. Yes, .007-.009 would be way extreme.

 

[K22]

Well, duh, it's 7-9 tenths, not whole thousandths.
The mic I have has flat end - but I'm thinking that 7-9 tenths is enough to say that the case is significantly larger than the other fired cases, yes?

Speer did extensive research on pressure and case head expansion. They determined that case head expansion over .0005" (that's four decimal places) is indicative of excessive pressure.

The problem with trying to measure case head expansion using a flat end micrometer is getting an accurate measurement of the case head. The flat end can contact the rim or a bulge just forward of the case head which is not case head expansion resulting in an erroneous measurement. Also, you need a micrometer accurate to .0001" which is not the typical micrometer.

 

[jds holler]

Seems like 26 grains of BLC should pretty much fill the case??

 

[jelenko]

Seems like 26 grains of BLC should pretty much fill the case??

You would think. Turns out BLC2 is fairly dense. 26gr is 97% fill ratio.

 

[jelenko]

Speer did extensive research on pressure and case head expansion. They determined that case head expansion over .0005" (that's four decimal places) is indicative of excessive pressure.

The problem with trying to measure case head expansion using a flat end micrometer is getting an accurate measurement of the case head. The flat end can contact the rim or a bulge just forward of the case head which is not case head expansion resulting in an erroneous measurement. Also, you need a micrometer accurate to .0001" which is not the typical micrometer.

I'm using a Mitutuyo - it reads to one hundredths - I'm assuming it's accurate to tenths.
I'm eyeballing where to measure. I can say the readings are consistent within 2 tenths => I'm assuming measurements that are 7-9 tenths away are 'directionally' correct even if not precisely so.
What do you think?

 

[jelenko]

So, net, probably somehow too much powder got into that case.

And, as interesting to me is that the primer isn't leaking. I have 3000 cases primed with the Win 41's!

 

[K22]

I'm using a Mitutuyo - it reads to one hundredths - I'm assuming it's accurate to tenths.
I'm eyeballing where to measure. I can say the readings are consistent within 2 tenths => I'm assuming measurements that are 7-9 tenths away are 'directionally' correct even if not precisely so.
What do you think?

Measuring case head expansion requires some experience to derive meaningful results. First, you need a baseline. The Speer study used once fired cases as the baseline since they determined this provides the most meaningful baseline. They also conducted measurements for only three test firing before retiring them for further load testing due to work hardening. I quote from their study, "a blade micrometer accurate to .0001" is mandatory."

The goal was to test loads for excessive pressure using case head expansion as the parameter which they determine there is a positive correlation between case head expansion and pressure. Often excessive case head expansion will also reveal itself in loose primer pockets.

In my opinion and I am not a gunsmith, this method requires a skilled technician with proper equipment to achieve meaningful data.

 

[243winxb]

high pressure

Yes.
Brass used? Range brass or mixed headstamp? Brass that is heavier, less capacity, makes higher pressure.

Neck tension needs to be .002" or more to prevent early bullet movement. More so with the 41 primer.

Barrel length to get your velocity? Hodgdon lists 24"

Your COL is longer then Hodgdons 2.245" Your 2.290" seems long for the magazine?

Trim length ok?

Lubing inside case necks with what?

 

[jelenko]

Yes.
Brass used? Range brass or mixed headstamp? Brass that is heavier, less capacity, makes higher pressure.

Neck tension needs to be .002" or more to prevent early bullet movement. More so with the 41 primer.

Barrel length to get your velocity? Hodgdon lists 24"

Your COL is longer then Hodgdons 2.245" Your 2.290" seems long for the magazine?

Trim length ok?

Lubing inside case necks with what?

View attachment 1553885

Brass is all Wolf with the same number of firings [2] Bought from Wolf when they were selling primed brass.
Neck tension is between 4 and 5 [I like 3 but I sent all this brass out for processing]. All trimmed to 1.750 +/- 3.
Barrel is 24".
I'm using ASC and PRI mags - both have room for up to 2.31 COAL. I'm using 2.290 COAL so there is no crush of the bullet into the powder. Even though the fill is only 97%, using a Dillon powder measure tends to fluff up the powder.
No lube in the necks.