Danger of powder charges that are small in relation to case volume?

Thought some of you might find this interesting....... there's a thread over on the CMP forum about a guy whose 1903 (bolt action 30-06) blew apart while he was shooting a match with his reloads. The general consensus is that it happened because the charge amount for 30-06 in the powder (Accurate 5744) he was using only fills the case by about 50%. Anyone ever heard of about this and why a small charge (in comparison to case size) can be dangerous?

The thread is here in case you want to read it. The 4th post down is where the actual guy whose rifle blew apart chimed in and began giving all the details about his handloads.
http://forums.thecmp.org/showthread.php?t=247551

Don’t even need to read the thread, he double charged a case.

JimB said:

Don’t even need to read the thread, he double charged a case.

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Not necessarily - you really should read it. Someone posted a quote from a "Shooting Times" article back in 2009 where the author (who worked for CCI at one time) talked about some testing they were doing which showed that small powder charges in relatively large cases can be no bueno. People usually only worry about overcharging a case, but this would indicate that doing the opposite could be dangerous under certain combinations of powder, primer, case, etc.

The theory of charge detonation was explained to me as similar to a dust explosion - flammability increased by surface area. The increased surface area (50% case volume laying on its side versus the diameter of the case for a 100% charged case) of the charge that is exposed to ignition by the primer results in a pressure spike due to a larger volume of powder being ignited initially, versus the powder burning from the case head to the neck as is normal.

It makes sense to me to a degree, but I suspect that slower burning powders are more susceptible to this than fast burning powders simply because there would be a more significant difference pressure due to burn rate from a normally charged case volume.

Railsplitter said:

Not necessarily - you really should read it. Someone posted a quote from a "Shooting Times" article back in 2009 where the author (who worked for CCI at one time) talked about some testing they were doing which showed that small powder charges in relatively large cases can be no bueno. People usually only worry about overcharging a case, but this would indicate that doing the opposite could be dangerous under certain combinations of powder, primer, case, etc.

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There have been many many threads about this, and lots of theories. It happens often enough that there is a decent argument that it happens for some reason other than over charging, but then it hasn’t been replicated.

Let me take a moment to apologize for being condescending and dismissive. It’s a topic worth consideration, it just always ends up in the same place.

We do have a resident expert in "internal ballistics" that we may get to chime in. I recall @Michael458 just posted about pressure testing he was doing and perhaps he has run into this or is more familiar.

I for one would like to understand it better so as not to "step in that pile of pooh".

Hi guys....... I just walked in, and have to leave very shortly, so not a lot of time......

I have done numerous very light loads, using almost no case capacity in several different cartridges, such loads as a few grains only for subsonic 223 and 308, talking 3-4 grains of Unique in 223 and 8-9 gr of Unique in 308. I forget some of the 300 BLK subsonic, but very low charges, faster powders. Zero issues, and no pressures. Lots and lots of light loads in big bore rifles. 1/2 or less case capacity, zero issues. No pressures. Light loads in the big nitro cases, now here, you can experience Hang Fires with lighter loads and too much air space.... Click-------Bang...... Those are disconcerting at the most, never pressure issues.......

I was trying to read some of the thread that is referenced directly concerning this issue, I have not had time to finish yet. But I did see that the shooter fired 2 rounds, same load supposedly, and the gun blew on the 3rd round? My question on this, if this was a direct pressure issue, with the 50% full 30/06 case and AA 5744, then why did the first two not show any pressure signs at all????? The 3rd round sounds like it blew the gun all to hell! The first two there was not even heavy bolt lift? I suspect another issue personally. This evening, I am not convinced even slightly there is an issue with 50% full case. Powders can and do react strange at times, so many things are still possible that I don't know about. However, my experience says this is not the case.

I will have more time to take a closer look tomorrow morning, will do and report anything new or different I might find, either in my notes, or the referenced thread that may answer more on this.

Also, I am not opposed at all to doing some real test work, real pressures, if anyone is truly interested and really does want to know. But that will have to be a few weeks from now, so in the meantime, if you guys can come up with some ideas of things you might want to test, we can look at it. I have 308 set up for pressures, we can get some brand new AA 5744 or other powders, and try some light loads, and get real time pressures and find out for real.....

But let me take a closer look tomorrow and see if I can pick out anything else. Running out of time... .But answer me this, fired two rounds, just dandy zero issues and fired the 3rd one and the gun blows??????? Hmmmmm, I smell something else afoot on this.................

Thanks for asking, and we will touch base again in the morning...
M

As CharlieR mentioned, the theory is it has to do with the significantly greater surface area of powder being exposed to the primer flash. Theoretically, the first two rounds could have caused the powder to bunch to the front of the 3rd round, causing some sort of anomaly. Even if it's not a danger, it is recommended that some sort of filler be used so that the powder doesn't have this variable, which can effect accuracy. I haven't read the article, but based on the idea that it was a less than 50% case volume, that opens the possibility of a double charge. And I'm inclined to agree with JimB's first assessment of a double charge as the most likely cause.
I had a friend load up some .45 Colt with some light load Bullseye, and double charged a case. She, discovered it while shooting at an indoor range, where she worked. Fortunately, it was in a Ruger, so no physical damage was done. But, she said, when that round went off, she stood there for a moment as she assessed what happened, she put the gun down on the bench and went outside and smoked a cigarette.

JimB said:

There have been many many threads about this, and lots of theories. It happens often enough that there is a decent argument that it happens for some reason other than over charging, but then it hasn’t been replicated.

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Correct. I read the listed thread again this morning.

One, to begin with, this is a very odd choice of powder, for the purpose he intends. I am no expert at all concerning the type match they were shooting, along with whatever common practices they might be working with. AA 5744 is very commonly used in a variety of cartridges for reduced loads. I also had a look at the AA manual and AA 5744 is listed for 30/06 for LEAD or cast bullets, 160 gr to 200 gr, 22-27 gr giving around 2000 fps. No mentions for any other bullets in this cartridge. I can't even imagine where or why one would choose this powder for I believe it was a 155 gr jacketed bullet. ??? However, that being said I have done a lot of things that are way out of normal, and have even blended my own blends here in search of "magic Powder"................

He states he was using 30 gr of AA5744 with the 155 gr bullet. Also stated he had fired up to 75 rounds of these prior to this match. Obviously no issues. Then fired two rounds in this match, and fired the 3rd which blew the gun.
Thats 77 rounds fired, no signs of pressures and now all the sudden there is the ONE ROUND that blows the gun......

There are about just under maybe a MILLION other reasons this could have occurred, and maybe not a 50% full case. I blew a gun one time, but I broke the rules of paying attention to what I was doing! Loading a 6.5 WSM, slow powders, and I think the test load was H-4350, or was supposed to be. Phone rings, I get on the phone, not paying attention, I pick up a can of H-4198..... It was "H"................ Not good results, locked it up tight, worse than just locking it up. Pressures would have well exceeded 100'000 PSI I am sure. Gun held together, but was stretched beyond use again.......... Picking up the wrong powder, distracted by the phone and probably more stupid stuff too....

Yes, it might have been undercharged! The 2cd round fired in that match might not have had a full charge. So much so, that the bullet stuck in the barrel, and the 3rd round had no release for the pressures. Ka-Boom!

And many other things too........

While I won't totally 100% dismiss the "light charge-larger case volume" possibility, I seriously have doubts, if for no other reason that I have done it 1000s of times with various different cartridges, powders, and combinations.
While the vast majority of the time, when I go to lighter charges, I use a faster powder, there have been times I worked with much slower powders. We have worked with fillers here many times, fillers are commonly used in big nitro cases to remove the air space. Extremely large cases like these do odd things as well. I mentioned above about Hang Fires, and fillers are used to try and stop this sort of thing from occurring. Fillers can be dangerous, far more so than half filled cases, or hang fires. We did a filler test once with 470 Nitro to prove the point.

I did a google search on this as well. I did not spend very much time reading anything in detail mind you, but every case I saw was much the same as JimB states above.... Lots of threads, lots of theories.... and has yet to be replicated in the lab. My Theory? My theory is this, if it can't be replicated under controlled conditions, repeatedly can't be replicated and proven, then I would tend to believe that other factors are involved.

Everyone can screw up at the bench. I have, I suspect many of you have as well. Not saying anything, just saying "S**T Happens".
Have a nice day.........

Michael458 said:

Everyone can screw up at the bench. I have, I suspect many of you have as well. Not saying anything, just saying "S**T Happens".
Have a nice day.........

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Yep, doo-doo do happen!




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Here's an article recommending 5744 in general for reduced loads as @Michael458 says above.

I read somewhere about a theory on low case fill rifle loads blowing up. The theory was that if the powder is forward in the case, it is a long way from the primer. The primer will detonate and have enough power to push the bullet into the lands, but the powder does not immediately ignite. The powder will ignite shortly after the bullet has been jammed into the lands (stuck) and this can cause the pressure to build, much like a barrel obstruction.

Don't know if it is true, but it sounds plausible.

When I have tested revolver loads, I will do a "powder forward" test. I will shoot 3 rounds, starting with the barrel pointed up, bring it down to line up with the target, then fire. This is the "powder rear". Then do the same thing, but start with the barrel down. This is "powder forward". I've seen over 300fps difference with some powders. I don't use any powder that shows a large variation.

There was a lot of talk about this about 15 years ago with the .45 colt. It was blowing up SAA colts (and replicas) often enough that it was a known issue, but not often enough anyone could put their finger on a cause.
The Colt .45 case has a lot of room for smokeless powder and the Cowboy action guys were pushing the lite load envelope. so you had even less powder in the already oversized case.
Bad reloads were the easy answer, but the working theory was that the conditions lined up so that the powder, that would be lying on the length of the case when the revolver was in the firing position, caught the flame kernel from the primer not on the end that would burn the powder end to end. But would instead ignite across the top of the powder all the way to the end of the case. burring all the powder at once instead of at the presumed known rate spiking pressure.
I dont know that anyone was ever able to prove it. Trailboss powder was born out of this.

Toprudder said:

The theory was that if the powder is forward in the case, it is a long way from the primer. The primer will detonate and have enough power to push the bullet into the lands, but the powder does not immediately ignite. The powder will ignite shortly after the bullet has been jammed into the lands (stuck) and this can cause the pressure to build, much like a barrel obstruction.

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Toprudder, when I load for the trapdoor, I will use large rifle magnum primers to help ignite any powder that is forward in the case. i do not think that I am filling 50% of the case.

nooneimportant said:

There was a lot of talk about this about 15 years ago with the .45 colt. It was blowing up SSA colts (and replicas) often enough that it was a known issue, but not often enough anyone could put their finger on a cause.
The Colt .45 case has a lot of room for smokeless powder and the Cowboy action guys were pushing the lite load envelope. so you had even less powder in the already oversized case.
Bad reloads were the easy answer, but the working theory was that the conditions lined up so that the powder, that would be lying on the length of the case when the revolver was in the firing position, caught the flame kernel from the primer not on the end that would burn the powder end to end. But would instead ignite across the top of the powder all the way to the end of the case. burring all the powder at once instead of at the presumed known rate spiking pressure.
I dont know that anyone was ever able to prove it. Trailboss powder was born out of this.

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Did Trailboss fix the problem?

JimP42 said:

Did Trailboss fix the problem?

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Trailboss is a very low density powder, you can pretty much fill the space in the cartridge and not get in trouble, and even with super light loads you fill a lot of the case.

JimB said:

it hasn’t been replicated.

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Michael458 said:

. Lots of threads, lots of theories.... and has yet to be replicated in the lab. My Theory? My theory is this, if it can't be replicated under controlled conditions, repeatedly can't be replicated and proven, then I would tend to believe that other factors are involved.

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Yep, the oldsters used to tell us this about 38 cases and BE. Never been replicated??? Never!!! Ain't happenin!

JimB said:

Trailboss is a very low density powder, you can pretty much fill the space in the cartridge and not get in trouble, and even with super light loads you fill a lot of the case.

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I meant did it stop the unexplained explosions... probably so, since whether they were double charges or instant detonations it would fix it either way.


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JimP42 said:

I meant did it stop the unexplained explosions... probably so, since whether they were double charges or instant detonations it would fix it either way.


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I know of no “unexplained” kabooms with trailboss.

JimB is right you could almost scoop load trailboss and be safe (Dont do that) It was an answer to the problem, but cowboy action itself started changing and more people were shooting .38 and then .32 revolvers instead of soft loading the Colt so the .45 Colt mystery kind of faded away.
I had heard about unknown .45 Colt detonations back in the 80's but information was scarce as there was not the volume of .45 colt guns and rounds fired as when cowboy action took off. Was it bad hand loads? too much pressure on old soft brass? too little powder that burned all at once pushing the pressure curve beyond what 100 year old guns could stand? No one ever found out for sure as far as I know.

Excellent coversation Gentleman.


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As a point of interest, right here on this forum, "45/70 Practice Load"......... we have Sharps40 loading 4-5 grains of UNIQUE in a 45/70 case for squirrel loads! Now 4-5 grains of Unique is not a lot of powder in 45/70...... and it seems his load has been very successful in completing his mission for many times over...........without blowing up because of too little powder.......

https://www.carolinafirearmsforum.com/index.php?threads/45-70-practice-load.46046/

Nope, not swallowing the big pressure from too little powder controversy, somebody gotta show me! And have to be able to duplicate it under controlled conditions........ We have never seen that issue here ever. But do pay attention to the "Filler" statement if you read that first post.

I have helped a few guys with subsonic loads in 223 and 308 here on occasion, I fall back on Unique, I think 9 gr of Unique for 308 and a 150 gr bullet, and 3.5 Unique for 223........ No problems, no issues....................no crazy pressures, nothing.......... Amazed at how good they were......

I'll add to the "probably can't ever know the whole story" side of the thread (s) by wondering aloud if the rapid increase in combustion chamber volume of a large bore straight sided case (compared to a necked cartridge case in a smaller bore) actually outstrips the ability of a light charge of fast burning powder (whether or not ignited all at once due to position) to generate excessive pressure......

Don't know. The wad free load works for me in my rifles. Your mileage may vary.

When I do my 30-30 with trail boss I still will take a small wad of toilet tissue to keep the powder pressed to the primer.

The posts that I have read and photos observed point to detonation rather than a high pressure burn, a big difference between the two. Accurate 5744 is beginning to develop a bad reputation due to guns being destroyed, enough that I have placed the powder I hold aside until a reasonable conclusion is reached for the destruction of the 03A3, a very strong action indeed.