After reading about a catastrophic failure due to an undersized charge using slow burning powder (in the medium caliber forum), I have a some questions because of a reloading practice I have. When developing a new load I often start 1 to 2 grains below the recommended MINIMUM charge and work up from there. I have always viewed that minimum charge as a "recommended" starting point and not something set in stone. I also seem to remember reading in the Lee reloading manual that a powder charge can be reduced below the maximum charge by as much as 30% except for very slow burning powders.

HERE ARE MY QUESTIONS:

What powders are considered very slow burning--that is, what powders are susceptible to detonation?

How much (in percentage) can one safely reduce the powder charge from the maximum listed charge for powders that aren't considered slow burning (susceptible to detonation)?

For slow burning powders (susceptible to detonation), how much can one safely reduce the powder charge below the maximum listed?

Finally, has detonation actually been observed in a controlled experiment? Do we know beyond a doubt that such is occurring?

Thanks for considering this topic.

NOTE: I'm not wanting to produce significantly reduced loads. I'm mainly concerned with my practice of starting a little below the recommended minimum charge. Plus, I'm just curious about this detonation phenomenon.

In my mind, my eyes, face, hands, ect are not worth hte risk. I start at minimum loads and work up from there. If I need more or less power, I change cartridges. Better to be safe than sorry. I think there are so many variables in the equation that there are very few absolutes.

Pretty serious questions to be asking in cyberspace. Perhaps you would get better information by contacting one of the powder companies.

I "BELIEVE" that "detonation" has been created in a controlled environment.

Any peril can be avoided by reading the books and using the books. Cross checking the data in each for a consensus. If 4 out of 5 books say the suggested starting load is xxx, why would you want to go below it?? One of the books even give you reduced load formulaes for practice or whatever. The Lyman 48th gives you loads to use with fast powder and cast bullets. Those loads would work also with jacketed bullets.

If you really want to build significantly reduced velocity loads and are concerned abt the possibility of detonation (and that makes sense to me ... one could ruin the hell out of your day) go to a powder like AA 5744 which is designed to burn effectively in partially filled cases.

For years (maybe until his death) Bruce Hodgdon swore that SEE (Secondary Explosion Effect) didn't exist. H4831, the prime alleged offender, was his bread and butter and he bristled at the suggestion that underloading it might be unsafe.

Ultimately, well-funded (relatively speaking) laboratories spent the time and money to research the issue and struck upon the "formula" which would often (but not always) result in SEE. That particular formula is not widely disseminated for obvious reasons, i.e., there is little good reason to tell someone how to try to blow up their gun. The reverse is true; that avoiding certain underloads with a particular set of powders will avoid SEE.

SEE can have less benign iterations than total gun destruction like relatively minor pressure excursions, but every now and then, when the moon, stars, and tides align just wrong, it can have spectacular results.

Most experimentation in this field has drawn the line on the faster side with IMR-4350 as the slowest powder that is subject to SEE. I suspect that this is a rather imprecise line and that the phenomenon depends on case size, bore size, and perhaps the weight of the bullet; thus it might show up with faster powders and not slower ones, depending on particular circumstances present. At any rate, powders in the IMR line like IMR-4895 seem not to fit the formula and there is no demonstrated
SEE phenomenon with that powder or faster ones in the IMR line.

Many powder manufacturers of non-IMR type powders, including slow ball and stick double-based powders, warn against underloading. Whether this is because those powders are actually subject to SEE or whether this is out of an abundance of caution, almost everyone will tell you NOT to go below listed "minimum" loads with virtually all powders as slow as IMR-4350 and slower.

H- and IMR-4895, IMR-3031, and IMR-4198 are often recommended as safe powders for reduced loads. 4895 seems particularly well-adapted to reduced velocities while maintaining low shot-to-shot variations and good accuracy. SR 4759 has been used for many years for further velocity reductions, and the relatively new "Trail Boss" seems well adapted to low-velocity loads in otherwise high-intensity cartridges. None of these powders has demonstrated any tendancy toward SEE, at least not at any catastrophic level.

Nicely written Stone Creek.
I have started with loads a ""little"" lighter than minimum recommended for many years with powders as slow or somewhat slower than the 4350s. Of course testing compents as I do pressure signs are always noticed. Never has the minimum danger load been sought.While following this practice there are times unburnd 4831 has landed in the snow.
to me it seems that with all the options we have why even fool around in this gray area.
If large reduction is sought than try the burn rates between 680 and 4320.But still use some smarts.

quote:

Originally posted by bartsche:
Nicely written Stone Creek.

+1
Straight forward, succinct and to the point. I might add concise and educational however I may be a little verbose here!
Well put Stone Creek, it’s refreshing to see information conveyed so eloquently for a change

In the name of safety, I need to mention the powder burn rate need not necessarily be slow to have an SEE in all circumstances. A Finnish Gunwriter's site (a little over half way down this page) has mention of a .308 destroyed by a load of 3.1 grains of Vihtavuori N320. This is a pistol powder between Bullseye and Unique in burn rate. So the fast powder being safe has at least that one example to the contrary.

There seem to be three different kinds of events that get lumped together under SEE, but that are not the same. One is exemplified by Norma's finding that loads that fill the case less than about 60% may expose a large surface of powder to the primer flash, thereby raising pressures. The old (1965) U of M study by Frank Brownell et al, shows the effect in a .30-06 case using IMR 3031. With that fast powder it does not appear very pronounced and the pressures, while climbing as charge decreases below a certain point, never get back up as high as a full charge pressure (see plots on pp 53 and 54 in this PDF file). This may not hold true for a slower powder, as Norma found, and may be the origin of the slow/fast dividing line. This is not detonation, but accelerated deflagration (normal burning).

Another type seems to be a burst at the muzzle of a gun, as Texas Gunsmith Charlie Sisk has been able to blow the muzzles of .338's with on demand. This is not a reduced charge situation, and happens only when a powder too slow for the weight of the bullet is employed. It appears to be a kinetic event rather than due to powder explosion.

Then there is actual detonation, where ignition progresses by shock wave rather than heat of the flame (deflagration). This is likely what the Finnish gun writer had happen to him, as double, triple, quadruple, or even quintuple charging the case would not normally exceed .308 pressure. So, the explosion can't be explained by a double charge.

Detonation can't normally happen to gunpowder because the grains make discontinuities in the shock wave path. The only exception I've heard of is when it is piled up in very large quantities so its grains are pressed together hard by weight of the pile, so they can act collectively like a fluid to carry the shock wave. This takes quantities on the order of tons, IIRC.

In the small quantity in a gun, I expect, if they (the labs) every narrow the conditions completely down, they will find it requires a mass of powder isolated in some corner of the case be fused by heat, then detonates. If you've had a load of 296/H110 squib out on you, a look in the case reveals what looks like a fused lump of tiny yellow fish roe. We had a picture of that up at the Shooters Forum within the last year. Within the last five years, one of the moderators had a squib of 4831 (speak of the devil) that did the same thing; fused in the case.

Research on engine knocking has shown heat alone can trigger a detonation in fuel and air mix (no mysterious wave reflections required). I'm not sure what the exact mechanism is in a gun? I only know that MathCad converts the energy in a fused lump of powder, if released simultaneous, to over half a million psi local to the lump before the gas has time to spread. Good way to start a crack in adjacent metal.

So, be careful. I've gone to IMR Trail Boss for light rifle loads. Works fine per their instructions and has plenty of bulk and burns extremely clean.

Nick

Excellent thread, thank you all!

quote:

Originally posted by Red C.:
...When developing a new load I often start 1 to 2 grains below the recommended MINIMUM charge and work up from there. I have always viewed that minimum charge as a "recommended" starting point and not something set in stone. I also seem to remember reading in the Lee reloading manual that a powder charge can be reduced below the maximum charge by as much as 30% except for very slow burning powders.

Depending on ALL the components involved and the specific Cartridge, that can be Safe or create the potential for a Ka-Boom. It is best to use the Min Loads shown in the Manuals as a Starting point.

quote:

...what powders are susceptible to detonation?

All of them - when improperly used.

quote:

How much (in percentage) can one safely reduce the powder charge from the maximum listed charge for powders that aren't considered slow burning (susceptible to detonation)?

That is impossible to answer because of all the possible Component and Cartridge combinations. What works in one application can mislead people into Wrong conclusions about other combinations.

quote:

For slow burning powders (susceptible to detonation), how much can one safely reduce the powder charge below the maximum listed?

None.

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Finally, has detonation actually been observed in a controlled experiment? Do we know beyond a doubt that such is occurring?

Yes and yes.
-----

quote:

Originally posted by Nick:
...a .308 destroyed by a load of 3.1 grains of Vihtavuori N320. This is a pistol powder. ...detonation, where ignition progresses by shock wave rather than heat of the flame (deflagration). This is likely what the Finnish gun writer had happen to him, ... the explosion can't be explained by a double charge.

Hey Red C., Does that remind you of anything in particular?

http://www.hodgdon.com/PDF/Youth%20Loads.pdf Follow published load data/info from powder manufacturers. There is no reason to go below there recommended starting loads for the same bullet type listed.

Red, why do you wish to practice with reduced loads? Why not practice like you hunt?

I understand that as we grow older recoil is less fun, perhaps a better recoil pad, brake, or recoil reducing rest might help?

For the most part I stay away from reduced loads, but if I was to load them, it would be witha powder specifically mentioned in a youth load, or one designed for that purpose.

Stonecreek...he's the man!

Even though he goes sometimes he is my go to man for a challenging reloading question.

We argue politics once in a while though!

I doubt there is any iron-clad answer to this question. I can't help but wonder why anyone would even want to go below normal "start loads". The accuracy is virtually certain to be poor if for no other reason than the burn rate is highly variable at greatly reduced pressures.

Most light/slow loads (like those using cast bullets) use fast burning, easy to ignite powders. Those don't have any history of detonations.

The NRA/Am Rifleman once did a series of 30-06 and cast bullet tests striving to achieve near jacketed velocities with modest charges of "normal" powders such as 42+ grains of H-4831. They used half grain kapok or Dacron fiber filler tufts to hold the powder rearward and also put a pea-sized wad of lithium auto chassis grease between the filler and bullet base. Meaning, they didn't use light charges of normal powder even back in the mid 60s without special handling.

First of all.....my thumbs up to the reply by stonecreek.....it's very well done and just might be the finest reply one can get to this question.

I do take exception on this level however.....if it's real then it should be reproducible......and it's not or appears to not be! All the data I've read (so far) is "iffy" and lacking in substantive proof. I keep searching for another explanation and never find that either.

Until documented proof is available, I'm erring on the safe side and that's that there is in fact SEE and that the way to avoid it is to reload to the directions of the loading manuals......and that underloads are as much a "no no" as overloads....maybe even worse as we have a lot of good data about high pressure loads.

In my world the jury is still out.....but I'll assume the worst case scenario because it's just plain the reasonable thing to do!

Blue Dot ..... ?

Couldn't resist.



Stonie,

Outstanding post, Pal!

One can reduce the velocity of any caliber. But one has to use teh right powder.

We load many of the larger calibers - 460 Weatherby, 6557 T.Rex, 600 NE and 700 NE with reduced loads, and we have never had any problems.

Depending on howmuch reduction you want, you can choose the right powder for it.

For drastically reduced loads, we use pistol powders like UNIQUE.

Sometimes we reduce charges for rifles like the 308 Winchester, for the kids to shoot.

They love the idea of shooting a big bore gun sometimes instead of shooting 22 RF.

An important thing to remember is making sure you keep the powder at the bottom of the case against the primer.

We use several things for this. Like tissue paper, Kapok and the powder used to protect shot in shotgun shells.

We generally load the ammo we need the same day we shoot them here in our indoor range.

We use teh same proceedures in fireforming cases for our wildcats as well.

We use pistol powders, and inmcrease the charges until we get a fully formed case.

This depends on the make of the brass and the caliber.

quote:

An important thing to remember is making sure you keep the powder at the bottom of the case against the primer.

We use several things for this. Like tissue paper, Kapok and the powder used to protect shot in shotgun shells.

quote:

For drastically reduced loads, we use pistol powders like UNIQUE.

How important is keeping the powder against the primer with a powder like Unique???

I load .444 Marlins with a 250 gr cast bullet and 12 gr of Unique (case about 1/3 full) and NO FILLER.

They are very accurate and consistent.

I shoot them in a Win 94 Timber carbine. I like them for plinking, self-defense (keep it by the bed), and shooting varmints.

You can feel the powder roaming all around in them.

Originally posted by Nick:
...a .308 destroyed by a load of 3.1 grains of Vihtavuori N320. This is a pistol powder. ...detonation, where ignition progresses by shock wave rather than heat of the flame (deflagration). This is likely what the Finnish gun writer had happen to him, ... the explosion can't be explained by a double charge.


Hey Red C., Does that remind you of anything in particular?

Yes, Hot Core, it surely does and I don't want to ever experience something like that again. Since that event I've wondered if instead of a double charge, I may have experienced something like a detonation.

Thanks for your response.

quote:

How important is keeping the powder against the primer with a powder like Unique???

Most people who use some kind of filler do so in the belief that it will make ignition and velocities more consistent, not to avoid something like SEE. If you are getting sufficient consistency using Unique without filler, then introducing filler would seem extraneous and would potentially change the internal ballistics of a given load.

Unique is one of the oldest powders in continuous production and use. It was so named due to its versatile characteristics that allow it to be adapted to shotgun, pistol, and rifle. To my knowledge, no instance of anything resembling SEE has been observed in any of the applications of Unique.

quote:

Red, why do you wish to practice with reduced loads? Why not practice like you hunt?

I understand that as we grow older recoil is less fun, perhaps a better recoil pad, brake, or recoil reducing rest might help?

For the most part I stay away from reduced loads, but if I was to load them, it would be witha powder specifically mentioned in a youth load, or one designed for that purpose.

I must have left the wrong impression in my original post. I AM NOT WORKING ON REDUCED LOADS. I simply have been starting slightly below the suggested minimum because I have found that, at times, my most accurate load was slightly below the suggested minimum. Also, because some guns show pressure signs before reaching the maximum book charge, I decided that it would be better to start slightly lower than the minimum and work upward from there.

I am generally not concerned with the velocity I can achieve nearly as much as I am about accuracy. I'm sort of an accuracy nut. If the most accurate load is 1/2 grain below the suggested starting charge, that is fine with me. However, after reading the post I mentioned in my original post, I became concerned about this practice. (I think I learned my lesson concerning reduced loads a couple of years ago.) My suggestion for those who wish to shoot reduced loads is to be sure and use published loads for that.

Thanks to all for the posts, this has been interesting reading.

quote:

Originally posted by Stonecreek:

quote:

How important is keeping the powder against the primer with a powder like Unique???

Most people who use some kind of filler do so in the belief that it will make ignition and velocities more consistent, not to avoid something like SEE. If you are getting sufficient consistency using Unique without filler, then introducing filler would seem extraneous and would potentially change the internal ballistics of a given load.

Unique is one of the oldest powders in continuous production and use. It was so named due to its versatile characteristics that allow it to be adapted to shotgun, pistol, and rifle. To my knowledge, no instance of anything resembling SEE has been observed in any of the applications of Unique.

Thank you sir!!!

Stonecreek,

Could you specifically comment (if you dare) reduced rifle loads using Blue Dot???

quote:

I simply have been starting slightly below the suggested minimum because I have found that, at times, my most accurate load was slightly below the suggested minimum. Also, because some guns show pressure signs before reaching the maximum book charge, I decided that it would be better to start slightly lower than the minimum and work upward from there.

Ok, that makes sence.

One of my books has a seperate section for match loads for the .308 and 30.06. In some instances the match load starting point for the .308 is as much as 3-4 grains lower then the standard load section. In addition, just look at how different load manuals vary on a give powder and bullet weight combination. If you were 5% below a reasonabley normal starting load, I wouldn't expect it to be a big deal. If I was dealing with a realitively fast burning powder with a low load density to begin with, I probably wouldn't even do that.

In general a load density around 60% is a good candidate for a catastrophic flash over. Looking through my Nosler guide, the lowest load density I see is 75%. With that in mind, that's where I set my personal rock bottom, never going to drop below, load level. It also the guideline I use when working up loads with non-canister powders with less then perfect load data. Load to the base of the neck, drop back 25%, and work up. Starting this low has not created any trouble for my to date. Of course YMMV.

quote:

Originally posted by Red C.:
... Since that event I've wondered if instead of a double charge, I may have experienced something like a detonation. ...

I didn't think you dropped a Double Charge then(same as a few others), and I still doubt you did.

Just follow the Min and Max "recommendations" listed in the Manuals and you will be way ahead of the potential problem.

Best of luck to you.

quote:

Stonecreek,

Could you specifically comment (if you dare) reduced rifle loads using Blue Dot???

J. Lane Easter, DVM

I'd rather not go there. Do a search and you'll probably find it.

Yeah...but I trust Stonecreek. I think he shoots BD!

quote:

Just follow the Min and Max "recommendations" listed in the Manuals and you will be way ahead of the potential problem.

Now there's a novel idea for you....