I ran some tests with cast gas Checked bullets and IMR7383.
in my .358X404 The loads were all around 65gr. of the 7383. the bullet weights were 200gr. 210gr. 250gr. 260gr. 297gr. the accuracy was best with the lighter bullets but not bad with the heavies. However, the lighter the bullet the more delayed ignition there was ( click bang ).See posting in reloading forum for details. Filled to the top my case will hold 100 grains of aa4350 to give you an idea of case size. roger

Like I said over in Reloading, I'm afraid that load may be risky for "detonation," Roger.

Avoid CLICK-BANGS like the plague!!! Pull the remainder of those rounds, please. ... felix

OK, I understand he has a big case and has some air-space in the load because he used no dacron fluff nor Grex type filler holding his charge back against the primer vent hole.



But stick type powders like IMR 7383 aren't generally noted for "detonation" effects like the H110 series of ball powders can very rarely do to you, are they? I thought the IMR stick types of powder were considered pretty good for partial case loads?



(although IMR 7383 as an individual powder seems to like relatively higher pressures --fuller cases-- for the very most accurate shooting).



But click..BANG ?? It isn't that hard to light.



Could this also possibly indicate his round has a lot free headspace and the case is being driven forward some distance before hitting chamber-end features, finally being stopped cold and the wafer over the anvil in the primer is only then being finally totally crushed and ignited by the long slow primer pin blow?



I'm confused (again) and lacking a lot of the background for this one, so please forgive me if this is one of those "stupid" questions that come up on occasion.



Which gun is this anyway? It might be dangerous for headspacing, too.



Oldfeller

The first reports of "detonation" were with light loads of IMR powders like 4831 and 4350 in cartridges like the .25-06.

OF, Ricochet is indeed correct. True, single base powders are less prone to go wild because they are easier to ignite (less deterrents), but any wave action build-up, in long cases most especially, cannot be trusted one-iota to stay uniformily non-cancerous. Besides, I think 4350 has been reformulated somewhat, having much less external deterrent since the old days. There are probably more different folks making the single base 4350 speed because of its popularity, not to mention the ball powders around this speed chasing more power per unit measure. ... felix

OOOKay (mental file being created) ....



IMR 7383 IS a whole lot like a very slightly faster IMR 4831, know that already from playing with the 7 Rem mag. Could be same base stick with less deterrent coating? Who knows, looks very similar in grain structure. Old forms of some IMR powders could partial-case detonate. IMR 4831 was included in that group. Mil-Surp pull-down powders ARE old IMR powders.



Hmmmmmm .....



!!Watch out for click ...BANG!! possible symptom of detonation -- next time could be click ...!!BOOM!!



See, I told you I could ask an occasional dumb question. That don't mean I can't learn something from it.



Oldfeller

I sure wish I had the actual specifications for the IMR powders of this era from DuPont. All we can do is speculate about the differences. Since 7383 can't be loaded as densely, I think it has larger central perforations/thinner tube walls than 4831 or 4350. I don't know about the deterrent, but had speculated it was a little less. It's a little faster burning than 4831, and it was specifically designed for a cartridge rated at a maximum average chamber pressure of 38,000 PSI. That's considerably less than what 4831 was generally used at. The old .50 Spotter cartridge was originally loaded with 4831, and for some reason it was found advantageous to bring out 7383 and load that into it instead. When they made the changeover, the bullet weight remained the same. Nominal charge weight dropped from 120 grains to 110 grains. Muzzle velocity dropped 75 FPS, and maximum average pressure rose from 35,000 to 38,000 PSI. That's all the comparative data I've got.

Since it was a spotter round and it's only purpose in life was to match the arty round it mocked, perhaps they needed to slow it down 75 fps to be a better match to the arty round? They might have changed the arty projectile weight a bit, new fuse, new explosive, who knows?

Heck, it sounds sensible anyway, even though we will NEVER really know what they did or why.

Oldfeller

The projectile's weight stayed the same. Don't know about its BC. I figured it was a better match to the 106mm's trajectory that way.

Anyway, obviously the 7383's supposed to be a little bit faster burning than 4831.

In my little .22-250 and .30-06 it seems to fairly closely match velocities produced by equal weights of 4350 at the bottom end of 4350 loads. Can't get much past that due to this bulky powder's low loading density.

"Could this also possibly indicate his round has a lot free headspace and the case is being driven forward some distance before hitting chamber-end features, finally being stopped cold and the wafer over the anvil in the primer is only then being finally totally crushed and ignited by the long slow primer pin blow?"
No! My bolt handles for range shoting always close on the hard side. My hunting rounds are something else.These were test rounds for the range only.

65.5 grains of 7383 fills my case almost 3/4 full. It is not a very dense powder. Is it possible that the bullet is moving long before the needed pressure and temperature are obtained? In other words restricted or slow ignition maybe caused by the bullet not holdng long enough or strong enough to give adequate pressure rise befor the volume significantly increases.
The lighter the bullet the more unburned powder existed.Not hard to ignight? There were no high pressure signs at all.That powder was saying " You better hold me tighter if you want me to release my energy." and I wasn't wareing my hearing aid. roger

It's a coarse, slow burning powder with a relatively small burning surface area for the weight, and a deterrent coating. It's also bulky because there's a lot of air space within as well as between the grains. Reduce the amount loaded much below a full case and you're getting into the same loading density ranges where folks have come to grief with 4350 and 4831. The large air space for the primer flame to expand into means it's not as hot (seemingly paradoxically) as with a dense charge of powder that leaves little air space. The surface area of the powder that burns is small, and with a relatively cool ignition and slow burning deterrent coating, the initial production of hot powder gas is small. So you get a delayed ignition from the standpoint of generating enough pressure to move the bullet all the way down the bore. Indeed it can move the bullet out of the case, into the rifling and stick it there, though. That's one idea of how "detonation" situations can arise, when the bullet starts moving, stops, and is more or less jammed in place when the powder finally does really catch on fire. That start-stop situation may also lead to pressure waves reverberating in the chamber that have been theorized to be part of the problem. There are lots of ideas of how "detonation" occurs. Bottom line is, it's known to have happened with loads like yours above, so I'd steer clear of them for safety's sake. Use this powder in near case-filling loads and you'll be OK. It'll still leave lots of unburned powder in cartridges like the .45-70 that need a faster burning powder for efficient combustion, but whether or not that's a problem is a matter of personal preference. IMO it's a nasty mess. I'll use 7383 with full-case jacketed loads or perhaps with full-house loads with heavy hard cast 30-06 loads. I don't think it's suitable for mid-velocity cast loads at all, any more than 4831 is.

John,
Is there any hard evidence that this ever happened with lead bullets? I have no first hand data but didn't the explosive problems with 4831 and or 4350 happen with loads that approached or was below 50% by volume? Truely I'd like to put the boogy Man to bed and deal in facts and not hear say and theory.
First: I believe there is a real danger.I also believe that it is ill defined.
Second: Is this click bang scenario a degree of that problem or just a relative situation and not of the dangerous type at all?
Case in point( no pun intended )What would the result be if you had a nearly compressed load of 5020 ( 100gr. in the 358X404 ) and touched it off with a large PISTOL PRIMER? One thing for sure. You will push a lot of unburned powder out the barrel.
Does anybody have any real life bad experience with this type happening? Anything concrete? I promise I won't theorize it to death roger

Ricochet & Roger, I reported not long ago that I tried 7383 and IMR 4350 in my '06 with 125gr. jacketed bullets and was thrilled with the results. Ricochet is right: 55gr. 7383 takes up significantly more space than the same amount of 4350 (weighed .30-06 cases). I'm afraid that we have to accept the likely conclusion that 7383 isn't especially suitable for cast bullets. All is not lost however, since it performs superbly with jacketed bullets; and furthermore, where can you purchase 7lb. of any IMR (or Win., Hodgdon, et al) powder for $4.00/lb.? We've stumbled on a diamond in the rough and should appreciate it for what it is. ...Maven

Roger, hearsay and theory is all you can get on these explosions. I've seen statements on the old Shooters board that someone's figured out how to reproduce the effect at will, but nobody's published any sort of data. Just lots of ideas about how it might happen. And surely the explosions are just the far end of a phenomenon that happens more often, probably usually going unrecognized.



Firing cartridges with weak primers has indeed been shown to sometimes produce extra high pressures, though. My conjecture is that an initial slow burn preheats the powder grains to some depth so that a considerable portion of the powder reaches ignition temperature at once, rather than burning in a thin layer at the surface in an orderly, progressive manner. Not the same as true detonation, which travels as a shock wave at sonic or supersonic speed through an explosive solid, my proposed mechanism is really more like "knocking" in a gasoline engine. But it's purely my hypothetical daydreaming, that I have no way to test. There may well be more than one mechanism for abnormal pressure excursions to occur.

Ricochet I think that thread on the old Shooters forum was me and BruceB et al ringing out all our possibles on how SEE goes down. Your explainer is as good as I've heard BTW.

Bruce sent me an article by Roger Stover [?] of the Rocky Gibbs 'fan club'. He claimed to have been able to reproduce the effect at will but lacking real documentation to such I wonder.... note: BruceB I can't find the article at present and hope that's the correct take on it..

4895 no less has produced a high pressure event destroying a gun in a 30 BR using orange bullets. Fella was using a reduced loading to fireform[?]/break in the bore and the thang came A-part. So I think this SEE is possible in alot of numbers, not just slow fuels.

But I think that 'engine knocking' of Ricochets' is very close to what goes down.. IMO. You get partial ignition and the bullet moves down the bore a short distance and stops, the remaining chg goes off and the bullet in effect becomes an obstruction. I do think in some instances the original small amount going off does fracture the fuel and change the burning speed to a much faster rate.. further jacking up the psi's.

No one to my knowledge has heard of an SEE event with cast bullets. Anyone ever hear of one??

I did alot of messing with medium speeds at reduced charges yrs ago-- mainly 4320 and 4064 in 06, and all I got for several cans of messing was great accuracy.. No high psi's.....not that I was really look'n for them.

Here is some interesting stuff. "Modern Reloading Second Edition by Richard Lee. He has a short section on Loading lead,alloy cast bullets. The reading material is good but the eye opener is in the 308 & 30-06 load tables. One example:bullet cast 165gr. powder H 4350, recomended max charge 46 gr. recommended min. charge 23 gr. The tables are full of good stuff like this.There is nothing in or just prior to the tables that any of these loads were used with wads or fillers.

Also Richard references testing he has done that cleary illustrates that pressure remains the same and decreases the more you compress some slow burning powders. I mention this because I believe that there is a relationship here between it and what we have been discussing.
Mavis, I think what you said is correct,especially 7383 and lead bullets unless maybe you have a filler? Not having any vast experiece in the cast bullet area I can bring little to the table. roger

I just found an interesting explanation of "SEE" near the bottom of this page: http://guns.connect.fi/gow/QA6.html

Old Pete says that he's written a 20-page explanation of this in Finnish. He also references a German textbook by an author who was able to reproduce the effect at will in 1966. Too bad I don't have access to these and couldn't read them anyway!

His explanation is similar to mine, but he speculates it's combustible gases forming and igniting all at once.

I still doubt those stories of blowups with 3 or 4 grains of fast powders in rifles. I think those are cases of inadvertent multiple charges. That would be SO easy to do.

BTW, back to 7383: I got out shortly before dark today and fired 40 rounds of 30-06 (a bit more rapidly than I really should've in my light barrelled M77) loaded with 7383 under the 168 gr. FMJBTs just like Roger's and also 165 gr. Hornady BTSPs. Didn't shoot any off the bench, I was trying offhand, which I'm not too good at and I didn't have an opportunity to chronograph them, so I have no new data. But I did discover something VERY interesting. This was the first time I'd shot 7383 in nearly still air with the slight breeze drifting straight back into my face. (Whenever I've shot it before, it was very windy and blowing across or away from me.) On every shot I immediately smelled ammonia! Not camphor, which I recognize, and which is found in some Russian powders. This was ammonia. It was in the cloud blown out the muzzle, but the bore and the cases didn't smell of it. That tells me it was formed from the deterrent layer that burned off in the first gases formed. This powder must have a different deterrent than the dinitrotoluene used on nearly all IMR powders. It also can't be ethylene glycol dimethacrylate, which was used on at least a couple of military IMR powders. (That compound contains no nitrogen.) Looking at the generally known compounds used as deterrents or burning rate modifiers, the most likely candidates to produce an ammonia smell would seem to be Akardite II or one of the centralites.



I also believe this powder to have a small amount of carbon black added to it. This is included in quite a few modern powders to absorb radiant heat from the powder gases near the surface of the grains, enhancing surface burning and inhibiting deep heating of the grains by radiant energy. The reason I say it's in there is from my failed experiment with the .45-70. The half-burned grains of 7383 were jet black, while most partially burned IMR type powders I've seen have been translucent, honey-colored or in some cases (like the ADI-made H4350 and H4831SC) greenish.



This is interesting stuff. I sure wish I had the official maker's specs!

So, our common usage of magnum primers with higher density loadings of IMR 7383 does not act to greatly reduce the "outside chance" of this speculative detonation effect?

Why are you guys even talking about using standard pistol primers with the stuff? It isn't that easy to light, either. Plus the pistol primers ARE NOT going to withstand rifle-level loadings of anything very well.

I am beginning to sense this discussion is not a real report of a real issue, but is somebody having some fears about a "possibility" that actually stems from information generated from a -what if- discussion session from long ago.

Has anyone really, actually factually had a documented detonation effect from IMR 7383 pull-down powders? Or from IMR 4831 (any vintage)?

Even if it was from a "guy fireforming some BR cases" are there any facts or evidence to back any of this up?

Oldfeller

Yes, OF, it's true. For safety sake, it does not need to be "backed up". Believe it! Aladin, it was me who reported the SEE condition using 25 grains H322 (first issue to public) behind 311291 at 180 in a 308W Browning from Europe, 300x308, with SAMMI minimum chamber by luck or accident, more than likely the latter. I used normal WW LRP at the time. I still have some powder from this lot left, some of the same primers and boolits. I will supply rounds made up from the SEE lot and the gun to any worth while lab. This load produces a SEE on every shot, but each shot, at a down angle of about 30 degrees, produces pressures that will always require a board to open the bolt. ... felix

Ammonia? Possibly some sort of hydrazine derivative included in the propellent? Could NOH be the oxidizer? I'm no chemist, but I can speculate with the best of them. <GGG>

"Documented" instances of SEE? Is that like a hole-in-one, where it has to be wittnessed? Here's some "documentation:" I've had some "click-bangs," followed by rounds that seemed to have an inordinately powerful recoil for the powder charge. Sometimes the click-bangs themselves have a high level of recoil and report. This was back in my early days of reloading, long before I'd ever even heard of "SEE." Were those cases of SEE? I dunno, but I do know enough now to recognize them as danger signs, and not something to just shrug off as I did then.

I'm with felix on the causes of SEE. If we're choosing up teams, I'm on the side of harmonic reinforcement of pressure waves in empty space inside the case, similar to a shape charge. Powder position and empty space inside the case would account for the non-repeatability of the phenomenon, since everything would have to be perfect for the shock waves to come together in just the right way to explode instead of burn properly. It seems to me that somewhere, there must be some explosive engineers that have done some real studies on this.

More than good enough Felix, I was just hearing Aladin say it might have just been another of his "conversations about what if" and wanted to sort the hard facts from "conversation".

Thanks for clarifying. SEE has happened to Felix with H322 an "early issue to the public" mil-surp ball-type powder in a light 25 grain powder load behind a "heavyish for the caliber .308 Winchester" 180 grain cast lead bullet load.

This is not out of line with the H110/W296 reports from the pistol world, a light charge of fine ball powder behind a heavy bullet resulting in an explosion effect.

IT DOES SAY that heavyish cast bullets in rifles can do SEE with fine ball powders and is consistent with the cast bullet SEE in the large caliber pistol realm with H110/W296 fine ball powders.

This still leaves the IMR stick powders innocent though.

========================================================

??? Anybody got any hard occurances of an IMR stick powder going SEE on them ???

========================================================

I am damn curious about SEE and them stick powders, as I use the the IMR sticks for everything half-power and up in a rifle (mainly due to metering issues with rotary drum powder measures). I have always thought that the IMR sticks didn't do SEE (and I use very very heavy for the caliber cast lead bullets all the time ........)

Backing off on the sticks has been safe for me to do so far. That is why I keep asking for the IMR stick SEE information.

If it has happened really, I want to know about it.

Oldfeller

OF, pard, H322 is, IS, is a very small single base stick powder! Hopefully, the formulation was/has been improved since the first issues. Maven has been using it with very good results lately is some large cases with cast. Might not be exactly the same stuff that I have (mostly had). It was/is a very good 6PPC powder, albeit dangerous to some extent, especially excessive vibration, like banging on a bolt with a hammer with a loaded round in the chamber. It will go off. Someone was killed doing this very thing on the BR circuit. NOT emphasized by the rags, naturally. ... felix

Roger, I don't think IMR 7383 kindly to fillers of any sort (more to follow) as it's a bit touchy as it is (and fairly clean-burning too) and I'm using standard LR primers. Some of the slower milsurp powders, e.g. WC 860 and IMR 5010 (even chunkier than 7383!) can benefit from fillers, namely Grex and powdered bran (You buy it as bran, but run it through a coffee mill at home.). However, you don't need more than 1.3cc (Lee dipper) in '06 to 8mm Mau. cartridges and frequently a lot less; e.g., .3cc in my 8mm Mau. with 195gr. to 236gr. CB's over 48-49gr. IMR 5010 (LR mag. primers). The problem with fillers is threefold: (1) They increase pressure (but give a cleaner burn and more uniform velocities, ES's & SD's). (2) They introduce another step in reloading. (3) You have to use enough powder (at least 80% of case capacity) to insure a compressed load. In addition, they work best in bottle-necked cartridges larger than the 6.5 x 55 Swe. Mau. I.e., you can use it in the Swede, but the results aren't worth the extra effort. Oh yes, don't even think about these powders (with or without fillers) in the .243Win. ...Maven

Oldfeller, Since IMR 7383 was thought to be akin to 4064 and 4350, I loaded it (starting loads) as I would either of them; i.e., with standard LR primers and jacketed bullets (My friend Vly's experience with it in the K-31 with CB's wasn't encouraging.) I've done that ever since and have been getting smaller SD's than with 4350. Here's some data (LR standard primers) for my .30'06 (22" bbl.):

52 gr. wi. 150gr. jacketed (mixed) -> 2,533 +- 14fps
52.5 " " 180gr. " " -> 2,426 +- 26 " _

Oldfeller, I ran out of space. Here's more '06 data:
52 gr. 7383 wi. 168gr. Speer HPBT -> 2,470 +- 13fps
52.5 gr. 7383 wi. 168gr. Speer HPBT -> 2,500 +- 20fps.

55 gr. 7383 wi. 125gr. Sierra SP -> 2,697 +- 22fps.

Btw, there was never even a hint of SEE with the above loads. ...Maven

Felix, appologies -- the H designation threw me, I always thought it refered to ball powders (I do learn something new every day).

Sorry, I was simply wrong.

Maven, you make me feel better about IMR 7383 as the little tiny sticks Felix is describing are getting really tiny and the IMR powders I use are anything but tiny.

IMR 7383 is a normal sized IMR stick and IMR 5010 is a huge stick, 150% the size of a normal stick.

I think I am going to plan to start liking Aliant 2400 a lot more for my lower mid-range loads anyway. IMR 7383 isn't sterling accurate in the lesser loads.

Thanks guys,

Oldfeller

Oldfeller, Right you are about IMR 5010: It's downright chunky! It's burning rate (or absence thereof) dictates mag. primers, loads which just about fill the case, and heavy CB's jammed into the rifling. You can improve its efficiency by adding a small amount of filler (powdered bran a la Aladin) or Grex. By small amount I mean between .3cc and 1.3cc in '06 and 8mm Mau. sized cases, which is enough to bring SD close to 25-30fps. BCR has successfully used it in his .270Win., but I don't know whether it will work in the narrow necked .25-06, 6.5 x 55, or similar cartridges. Btw, 5010 isn't powder measure friendly, so be prepared to use a scoop of some kind. ...Maven

Ain�t never been to the North Pole, but I�m certain that it exists�Ain�t never been to the dark side of the moon, but I�m certain that it exists�Ain�t never seen SEE, and I AIN�T certain that it exists, at least not for the reasons we have been told cause it.

I am always interested in reading the thoughts/experiences concerning this subject. If one takes a total of all the rounds reloaded and shot by all the people that post on this website, plus all the people who reload and shoot that don�t post on any website and ask them if they have ever experienced SEE, I bet the percentage of people who have experienced it (or something like it) will be absolutely extremely small. And I would bet that the very small percentage of people who have experienced it made some type of mistake in the reloading process or there is a problem with a specific lot of powder produced by a manufacturer. Maybe this is the case with felix being able to produce SEE on demand. Maybe that particular lot of powder is faulty???

A friend of mine completely wrecked a Model 59 Winchester shotgun�He thought Green Dot was O.K. to use in place of Unique! After all, they are made by the same company�

A cousin of mine was shooting at my shooting bench and the first 357 Mag round went �pop�. He pulled the hammer back and was preparing to fire the second round from his Ruger. I stopped him. The first round was stuck in the barrel. Apparently only primed the case and no powder. Could this have been mistaken for SEE if he had fired the second round�

And, just the other day I was going to load some 311041�s for my T/C in 30-30 using WC-860 (1300 to 1400 fps by the way!!!) When I was getting ready to put the powder in the powder measurer I realized I had a keg of WC-680!!! Could this error have been mistaken for SEE if I had loaded the cases and dropped the hammer�

And so this topic of SEE goes and will continue I am sure. Hope I continue to be as lucky as I have been for the past 35 years and not experience the SEE syndrome.

Now to the IMR-7383. Been using it some in the 30-30 in the Contender. Thirty-one grains of the stuff and the 311041 bullet. Accuracy has been pretty fair at 100 yards�excellent at 50 yards. So far I like it. The 7-30 Waters will be the next recipient of this powder�BCB

I've been using 7383 since Hi-Tech started carrying it. I've found that a lightly compressed drop tubed ( poured slowly thru a 30" tube into the case) charge is needed with heavy cast/jacketed bullets and standard rifle primers. This is not the same if you fill the case out of the powder measure and compress it. I've tried fillers and mag primers to no avail to. With the tubed charges, the accuracy is much better, but it still leaves a little powder in the bore.

bartsche,

31 grains of the IMR-7383 is a slightly compress load in the 30-30 with the 311041 seated to form an OCL of 2.612". Haven't chronographed it yet, but I am planning on doing so when we get a break in the weather. I will try it in the Waters also, but it may be a half-hearted attempt! I shoot WC-844 and the 287346 slug and accuracy is M.O.A.(most of the time) out to 150 yards. I hate to try to improve on that!!! Even if I did, I doubt I could be the person doing the shooting!!!BCB

I've got to make myself a drop tube and try that. I'd been loading this stuff by vibrating it down as the case fills, full to the mouth and compressed down with flat nose bullets in .22-250 and .30-06, and those loads worked very well. But I messed up some .30-06 cases in a hurry when I tried seating boattail bullets in those. Powder jammed between the bullet bases and case necks, bulging the cases and in a few cases collapsing the shoulders. So I backed off real quickly to just filling from a powder measure to the base of the neck, which means those loads are extremely mild. Perhaps a drop tube would let me get a little more in and just fill to that level. Perhaps a powder compression die like some of the BPCR guys use would let me mash down a caseful to a safe level prior to seating the boattails.