Secondary Explosion Effect (SEE)

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303PV posted this 4 weeks ago

 A search has shown that this subject has been discussed before, but I would like to get some recent opinions.   I have been reloading cast bullets since 1975. I read the first edition of the Lyman Cast bullet handbook and I started from there. I read the original article about Cast bullet loads in military rifles published by C.E Harris that I liked very much because of the systematic approach.  Since then I have shot many .. many thousands of cast bullets. Recently I have seen a lot of discussions on German reloader forums that the powder volume should not be lower than 80%. Vihtavuori mentions in their 2021 reloading guide (german version)." Risk of detonation through reduced loads etc" Quick Load also warns for a SEE. Are these warnings, caused by product liability concerns? More discussions on the internet?  A mystery factor created by infallible people who won't admit that they could have put a double charge in the case? I have only used fast-burning pistol and shotgun powders or the fast rifle powders like N110.

Please help to put my mind at ease. 

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99 Strajght posted this 4 weeks ago

Yes it does exist. I have had it happen and I can repeat it. I have never had it with cast and have been shooting cast for 60 years. Follow these rules. Stay with the faster powers. Be careful of slow powders and less than 3/4 a case full. Seat your bullets to almost touch the rifling or more. Handloader has a lot of good articles on SEE.

Glenn  

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RicinYakima posted this 4 weeks ago

Norma, the powder folks, did a lot of research and published their findings in the 1970's. Think the results were published in their booklet called "The Gun-bug's Guide". 

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Wheel Weights posted this 4 weeks ago

It may or may not be true BUT why take the chance ? So many powders work fine why bother ?

 

Harry Pope didn't have 4831 and he did okay.

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beagle6 posted this 4 weeks ago

The first I ever heard of SEE was a report by Jack OConnor when he was shooting editor for Outdoor Life Magazine. He was loading 60 grains of 4831 for a 270, if memory serves, and had his powder measure set for 30 grains. A double throw and he had his load. Evidently he didn't throw the second charge on one cartridge. I don't recall the damage but it shook Jack up. He reported it to the NRA who tried to duplicate the event without success. To my knowledge, no one has either. Seems to happen with stick powder slower than 4895 and 4064 and certain ball powders.

beagle6

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lotech posted this 4 weeks ago

I've read nothing about this in a long time, but the topic used to come up occasionally. Years ago, didn't P.O. Ackley attempt to reproduce the SEE effect using 4831 (probably H4831)? Does anyone recall this better than I do? Seems he was unsuccessful.  

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ray h posted this 4 weeks ago

I believe Ed Yard wrote about it in Handloader Mag many years ago.

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Squid Boy posted this 4 weeks ago

I think one of the best decertations on SEE was in a Wolfe publication called "Firearms Pressure Factors". There is a lot of detail about testing conducted by Col. G.O. Ashley and Lloyd Brownell. Both sides seem to make viable arguments about weather this phenomenon is a real problem or not. I have seen some very interesting pressure spikes that seem to occur after the bullet has left the muzzle when using a Pressure Trace system. I don't have a good explanation for them. I believe there are examples posted at the Shooting Software site. I am still not sure about it one way or the other although I do watch my load densities. Usually very divided opinions on this. Thanks, Squid Boy

"Squid Pro Quo"

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beagle6 posted this 4 weeks ago

Squid Boy

Regarding pressure spikes after leaving the muzzle:

back when the artillery was developing the M101 Howitzer ( 105 split trail) there were times when the barrels split at the muzzles. The problem was diagnosed as unburned powder detonating when it gained oxygen at the muzzle. The problem was solved by putting a reinforcing band on the muzzle.

beagle6

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Squid Boy posted this 4 weeks ago

That's interesting about the M101 but I have very little experience with it. I am considerably more experienced with the M102 but I never saw or heard of a muzzle split in that gun. Also, I could not find a picture of a M101 with a muzzle band but I know they added a muzzle brake later. I wonder if that was the final cure by dispersing the unburned powder? None of the M102's had a muzzle brake that I know of. I suppose that the SEE pressure spike could be caused by the same phenomenon but 80K+ pressure readings after bullet exit do make you wonder. This is always an interesting topic. Thanks, Squid Boy

"Squid Pro Quo"

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Wineman posted this 4 weeks ago

Somewhere in my archives is the work done on Swede Mauser's in 6.5x55 and SEE. If I find it I will post but the Cliff-Notes are this:

The primer fires and the ignition and gas production of the powder starts. When sufficient pressure develops, the bullet is pushed from the case into the rifling of the barrel. In the Swede Mausers, that had issues there was considerable erosion at the throat and and the moving bullet (long and with a heavy jacket) would momentarily "pause" at this point. Rather than proceeding smoothly down the barrel it had become a bore obstruction. Since the pressure has nowhere to go, the weakest part, (cartridge case) now ruptures. These were with normal ammunition. A lot can happen in a short time.

Dave

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beagle6 posted this 4 weeks ago

Squid Boy

When I said a reinforcing band I didn't mean a separate band but that the barrel itself was machined thicker for the last 4 inches or so. Sounds like you are a fellow artilleryman

All my experience was on M101 's and M109 155mm. self propelled.

beagle6

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RicinYakima posted this 4 weeks ago

Yep that is the Norma study I remember. Also it didn't happen with a clean barrel in their testing, but only after it had been fired. It appeared that carbon in the throat added to resistance of bullet engraving. 

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RicinYakima posted this 4 weeks ago

I have no idea who Nick Harvey is but other than good grammar, it is just opinion. Nothing wrong with that, just not convincing. Bob Shell appears much more convincing and has done some things most of us have done over the years.

Thanks for the links WW.

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JeffinNZ posted this 4 weeks ago

Nick Harvey is a prominent shooting writer in Australia.

I have been churning through Handloader magazine from issue #1 through the late 70's then beginning again late 80's.  Many articles and all suggest SEE is not a real thing.  Never duplicated in a lab. 

Cheers from New Zealand

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Wheel Weights posted this 4 weeks ago

IMHO, there are too many choices in powder to take the most remote chance.

 

Just like the old rule of: "Always use a powder and load that will overflow the case with a double charge."

 

KISS is always my choice when available.

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Squid Boy posted this 4 weeks ago

Uncle Nick seems to be repeating the general story line regarding SEE but beyond a blown up rifle, I didn't see much in the way of data. I would like to know just who exactly is this ballistic laboratory that can cause SEE "at will". Since they are the only ones that have found the secret, why haven't they published this ground breaking data? Liability I presume would be the answer but wouldn't we all be better off knowing? Mr. Shell did a nice piece and covered a lot of options for reduced loading but again nothing firm. That's what I like most about this topic, you never run out of possibilities. Thanks, Squid Boy

"Squid Pro Quo"

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45 2.1 posted this 4 weeks ago

Uncle Nick seems to be repeating the general story line regarding SEE but beyond a blown up rifle, I didn't see much in the way of data. I would like to know just who exactly is this ballistic laboratory that can cause SEE "at will". Since they are the only ones that have found the secret, why haven't they published this ground breaking data? Liability I presume would be the answer but wouldn't we all be better off knowing? Mr. Shell did a nice piece and covered a lot of options for reduced loading but again nothing firm. That's what I like most about this topic, you never run out of possibilities. Thanks, Squid Boy

It was published back fourty years or so ago. They recommended not going below 80% load density for slow powders (slow for the cartridge). It was an excellent idea.............

 

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GP Idaho posted this 4 weeks ago

Talking to some about SEE's is akin to telling them you believe in Bigfoot. Personally, I'm just not taking that chance. Ninety % of my rifle loads are cast and if I do load jacketed bullets they are not reduced loads as I have no need of such.  In my cast bullets, most of the cases are charged with powders fast enough to put any worries of such an explosion to rest in my mind. It seems that the last article I read on SEE's concerned very slow military surplus powder loaded way below case capacity without a kicker charge. No danger of me going there either. Now, on the very fast powders, Bullseye, TiteGroup and the like I have no worries using VERY small charges.  If you're confident in your loading practice, load away. I'm just not confident in small charges of slow powder so I don't load them. Gp

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Squid Boy posted this 4 weeks ago

I think everyone here has read that about not loading below 80%. I have read it a hundred times and there is still no proof to back it up. Repeating it does not make it true and posting it in bold doesn't make it any truer. I think I have a valid question about anyone claiming to do it at will and not publish that data. And what is "slow for the cartridge" anyway? Who gets to say what is or isn't? How slow is slow? Of course it is only my own opinion. Thanks, Squid Boy

"Squid Pro Quo"

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