Blew a Primer _ Analysis

[DocDoc]

Ha ha...sometimes our communication with each other mimicks that between our spouses! What we said, what we thought we said, what we meant and what we heard
It's even worse when we attempt it electronically!

Yes indeed, 80% of the me sage is nonverbal, and those smiley faces don't do a good job.

 

[eshorebwhntr]

If the brass is the problem couldn't you take the data and components that have been been proven (I think you mentioned a 215 Berger combo @3100-3200) and work up to those levels in this lot of questionable brass?

My thinking would be that if this brass is bad, it'll be bad no matter what load you're using. Then you could just discard it or send it back to Hornady

Not sure how useful my idea is but it was just a thought

 

[Trnelson]

I have read the entire thread to this point. One thing that I would like to ask in regard to this issue. Am I correct in stating that the consensus opinion as to causation is likely a combination of the following:
1. Possibly a flawed piece of brass? Very, very difficult if not impossible for the average to discover even with controlling precisely for preparation and weight.
2. Possibly a primer favoring the small side of diameter mixed with a primer pocket that is favoring the large side of diameter? Which both would be possible to measure, but OMG...
3. Possibly a singular bullet favoring the extreme of the large side of diameter tolerances? Again, possible to measure.
4. The perfect storm of an unknown number of these variables that happened to converge at this singular piece?

 

[WildRose]

I have read the entire thread to this point. One thing that I would like to ask in regard to this issue. Am I correct in stating that the consensus opinion as to causation is likely a combination of the following:
1. Possibly a flawed piece of brass? Very, very difficult if not impossible for the average to discover even with controlling precisely for preparation and weight.
2. Possibly a primer favoring the small side of diameter mixed with a primer pocket that is favoring the large side of diameter? Which both would be possible to measure, but OMG...
3. Possibly a singular bullet favoring the extreme of the large side of diameter tolerances? Again, possible to measure.
4. The perfect storm of an unknown number of these variables that happened to converge at this singular piece?

There are a lot of unknowns here but it seems so far that the most likely cause was just a slightly oversized primer pocket and perhaps a slightly undersized primer but he said he didn't notice any lack of resistance when seating the primer. With the latter being the case it's just hard to know but unless it was really a seriously loose fit you wouldn't likely notice a difference in the amount of force required to seat the primer anyhow.

If he simply backs off a bit and then works back up if there are no repeats of the same we'll have our most likely possible answer

 

[Pdvdh]

I have read the entire thread to this point. One thing that I would like to ask in regard to this issue. Am I correct in stating that the consensus opinion as to causation is likely a combination of the following:
1. Possibly a flawed piece of brass? Very, very difficult if not impossible for the average to discover even with controlling precisely for preparation and weight.
2. Possibly a primer favoring the small side of diameter mixed with a primer pocket that is favoring the large side of diameter? Which both would be possible to measure, but OMG...
3. Possibly a singular bullet favoring the extreme of the large side of diameter tolerances? Again, possible to measure.
4. The perfect storm of an unknown number of these variables that happened to converge at this singular piece?

My feedback information & thoughts:
1) That's currently at the top of my "cause" list.
2) My position is no. I seat my primers with a K&M Services hand priming tool. It's pretty easy to ID light force seating of primers. If I have a loose seating primer, I investigate. If I conclude it's safe to shoot, even though it's not as snug as I'd like, I mark it with a Felt pen prior to firing it in my rifle. There were no size or strength related issues noted with the primer, IMO.
3) The bullets I've measured have been consistent in diameter, within my ability and the limitation of my 0.001" dial calipers, to measure diameters. I don't own a 0.0001" caliper or measuring instrument. Still, I can do a decent job detecting relative differences in diameter with my 0.001" dial calipers. After-the-fact problem is there's currently no way to measure the diameter of the bullet that blew the primer. Its GONE...
4) I dunno... That could be. The primary purpose for my thread is to expand the analysis of potential causes to include the knowledge and experience of other Forum members. So thanks for sounding in.

If the brass is the problem couldn't you take the data and components that have been been proven (I think you mentioned a 215 Berger combo @3100-3200) and work up to those levels in this lot of questionable brass?

My thinking would be that if this brass is bad, it'll be bad no matter what load you're using. Then you could just discard it or send it back to Hornady

Not sure how useful my idea is but it was just a thought

All my Hornady brass is from the same lot. I bought 2 - 50 count boxes at the same time and they both have the same Lot #.

For several years I've been using this brass with the 215gr Berger and a different powder (Reloder 33) with MVs ~3040fps. For a 3 month period of time the 225gr Hornady ELD-M and Reloder 33 at ~2980fps. This is the first large and noticeable surprise wherein a casing which received lesser pressure failed to hold a primer as if it was exposed to higher pressure, relative to any of the other brass casings.

Pretty sure Hornady will not reimburse anything for the used casings so I'm not going there. More significacntly, I don't expect them to spend any time tying to ID a flawed casing, let alone admit a defective casing slipped out their factory. Call me a pessimist in that regard, based on my life's experiences. A proud pessimist at that!

I don't think the majority of my Hornady brass is problematic, based on my history and experiences to date. But could a bad one slip thru their QA/QC every now and then and ship out for retail purchase???

RWS brass is consistently of high quality and strength, in my experience and opinion. I may discontinue use of this Hornady brass in favor of the novel option of using 8x68mmS RWS brass.

I appreciate the thoughtful Posts!

 

[eshorebwhntr]

You're most likely correct about the hornady brass but you never know. Sometimes companies will surprise you. I bought a bad brick of F215 primers back in 08 before the Obama scare. Never got around to using them until a few years ago. I was having all sorts of problems with pierced primers with mild loads. Some guys on here suggested everything from too light a charge to high neck tension. Anyway it did end up being the primers. I let federal know, they paid to have the primers shipped back, tested them, and confirmed they were bad. They gave me my money back.

It wasn't a painless process but I was impressed with their thoroughness. Never know...hornady might do the same.

Either way good luck getting to the bottom of it.

 

[elkaholic]

I had posted earlier that I had a very similar experience as Paul last fall and wanted to check the load again and see if I had the same result. The weather was very similar as when the situation took place last fall, and I had the same box of ammo sitting at the same temp and moisture condition, which was around 40 degrees with high humidity.
I thought it would be a good opportunity to check out the converted 8x68S RWS brass at the same time to make a comparison and also get some needed data for the possibility of being able to use it for the 30/375 S.I.
I have included 2 pics to illustrate the process of forming the brass and the result of firing the brass.
I used the same lot of powder and primer stored at 40 degrees with the brass so that conditions would be as close as I could come to the fall incident. The rifle was also cooled to the 40 degree ambient.
The load was 82 grs. N570, WW Mag primer, and 225 ELD. The RWS brass holds about 2 grains less powder, so more pressure was undoubtedly created than in the Hornady brass.
The pic of the 3 fired cases shows (1) the Hornady fired last fall (primer missing and extractor mark) the case expanded to .5325" at the web. (2) the same exact load fired today from the same lot (primer still in pocket but very flat) with the same case head expansion of .5325" (3) RWS 8x68 loaded with same exact load and component lots. Primer normal for a full pressure load, case head measured .5311". with no sings of over pressure! All of the brass was once fired with a full load prior to the test.
Just to verify things beyond a doubt; I fired the same load in the RWS brass 3 more times (4) total, and the web still measured just over .531" with a good tight primer pocket.
I realize that the only thing that this proves with certainty is that RWS brass is FAR
more tough than Hornady, which we all knew, but I think the case for Hornady brass being the culprit is growing pretty strong!

 

[Oldcappj7]

Rich, thanks for the post. No mention of any extraction difficulty either? What speed was that load running in the Hornady brass for you. Did you chrono the RWS passes for a comparison?

Jace

 

[Pdvdh]

Dang Rich!
The Hornady case head didn't support the primer face near as well as the RWS case! Very obvious from the photo. There was higher pressure in the RWS case, same primer in each casing, yet the primer in the Hornady case WAY flattened to an obviously wider diameter. The flat of the primer in the RWS brass is much smaller in expanded diameter.

For reasons I don't fully understand at this moment, the RWS case head is much more supportive of the primer. Two scenarios that could explain the difference...
1) A larger flash hole in the Hornady case allowed higher pressure to build inside the primer cavity resulting in extra outward expansion force at the back of the primer,
2) The primer pocket in the RWS case better supports the primer all the way out to the outer (back) face of the primer. Perhaps the primer pocket in the Hornady case flares out slightly as it nears the head of the case, allowing the primer to swell out further where there's less sidewall support. If so, this sounds like a primer ejection seat!

I did see that the Hornady case web expanded ~0.0015" more the RWS case web, based on your caliper measurements. But the flattened face on the primer in the Hornady looks to be more like 0.010" larger in diameter than in the RWS case. So the 0.0015" case web expansion doesn't account for the 0.010" primer face flattening. Something more going on here.

Beyond those observations, I agree with all of your conclusions. The photos, combined with your narrative description and measurements communicate very clearly. The RWS case has a much stronger case head and primer pocket, and will endure many more firings than the Hornady brass - with full pressure loads. And the Hornady brass is indeed the prime suspect as to the cause in my (and your), blown primers. The primer in the Hornady brass appears to be less supported, such that Hornady brass could be more prone to blown primers. Biggest issue I have with our Hornady cases is we BOTH blew primers with powder charges 3 to 3.2 grains less powder than we'd fired in other Hornady cases that held their primers. That hints of variable, inconsistent case head strength. That's a REAL problem for me. I can deal with lesser case head strength, as long as it's consistent. What I can't work with is the inconsistent case head strength. Inconsistent case head strength means I'll never be able to establish a safe baseline operating pressure. That unacceptable.

Thanks so much for the time and efforts you invested in this testing. This was very valuable and helpful to me. A fitting way to wind this Thread down. We aren't at 100% certainty on the cause, but we're close enough I'm moving on.

I'm shelving the Hornady cases. Ordering the RWS 8x68S cases pronto, for all future uses.

PS: There's no reason 375 Ruger owners couldn't benefit from the RWS brass also. They'll have to neck up in diameter and fireform, whereas we neck down and fireform.

 

[elkaholic]

Rich, thanks for the post. No mention of any extraction difficulty either? What speed was that load running in the Hornady brass for you. Did you chrono the RWS passes for a comparison?

Jace

I had no extraction issues. Nice and smooth! When I chrono'd it last fall at about 70-75 degrees, it was at 3050'. I did not check it today but the RWS has to be higher. I am wondering though if n570 picks up pressure at COLDER temps?

 

[elkaholic]

Dang Rich!
The Hornady case head didn't support the primer face near as well as the RWS case! Very obvious from the photo. There was higher pressure in the RWS case, same primer in each casing, yet the primer in the Hornady case WAY flattened to an obviously wider diameter. The flat of the primer in the RWS brass is much smaller in expanded diameter.

For reasons I don't fully understand at this moment, the RWS case head is much more supportive of the primer. Two scenarios that could explain the difference...
1) A larger flash hole in the Hornady case allowed higher pressure to build inside the primer cavity resulting in extra outward expansion force at the back of the primer,
2) The primer pocket in the RWS case better supports the primer all the way out to the outer (back) face of the primer. Perhaps the primer pocket in the Hornady case flares out slightly as it nears the head of the case, allowing the primer to swell out further where there's less sidewall support.

I did see that the Hornady case web expanded ~0.0015" more the RWS case web, based on your caliper measurements. But the flattened face on the primer in the Hornady looks to be more like 0.010" larger in diameter than in the RWS case. So the 0.0015" case web expansion doesn't account for the 0.010" primer face flattening. Something more going on here.

Beyond those observations, I agree with all of your conclusions. The photos, combined with your narrative description and measurements communicate very clearly. The RWS case has a much stronger case head and primer pocket, and will endure many more firings than the Hornady brass - with full pressure loads. And the Hornady brass is indeed the prime suspect as to the cause in my (and your), blown primers. The primer in the Hornady brass appears to be less supported, such that Hornady brass could be more prone to blown primers. Biggest issue I have with our Hornady cases is we BOTH blew primers with powder charges 3 to 3.2 grains less powder than we'd fired in other Hornady cases that held their primers. That hints of variable, inconsistent case head strength. That's a REAL problem for me. I can deal with lesser case head strength, as long as it's consistent. What I can't work with is the inconsistent case head strength. Inconsistent case head strength means I'll never be able to establish a safe baseline operating pressure. That unacceptable.

Thanks so much for the time and efforts you invested in this testing. This was very valuable and helpful to me. A fitting way to wind this Thread down. We aren't at 100% certainty on the cause, but we're close enough I'm moving on.

I'm shelving the Hornady cases. Ordering the RWS 8x68S cases pronto, for all future uses.

PS: There's no reason 375 Ruger owners couldn't benefit from the RWS brass also. They'll have to neck up in diameter and fireform, whereas we neck down and fireform.

Pretty eye opening for sure! A 338 based on this case might be pretty good, huh guys?
Or a 7mm!

 

[Oldcappj7]

Don't know on the temp. sensitivity of the N570. It took 84.3 of it to run 3060 in mine at around those same temps( mid 40s). Figuring on backing off a couple to start with on the 8x68mmS. Glad to hear it seems to be a viable alternative. Never "blew" a primer in the Hornady brass but had a lot of cases that wouldn't hold a primer after just a couple of loadings.
.....I know, just back off to .308 speeds.

Jace

 

[elkaholic]

Don't know on the temp. sensitivity of the N570. It took 84.3 of it to run 3060 in mine at around those same temps( mid 40s). Figuring on backing off a couple to start with on the 8x68mmS. Glad to hear it seems to be a viable alternative. Never "blew" a primer in the Hornady brass but had a lot of cases that wouldn't hold a primer after just a couple of loadings.
.....I know, just back off to .308 speeds.

Jace

 

[elkaholic]

Just noticed a misprint. My load was 83 grains, not 82