Another view on the matter. SEE?
From: "Norman Johnson"
Dear Sir:
I believe that your article warning of the dangers of SEE has inacuracies that will discourage some shooters from safe and satisfactory experimentation.
SEE is an unexplained pressure excursion which has often blown up guns. It is associated with markedly reduced loads of very slow powders.
Contrary to the ubiquitous old wives tale, detonation is NOT a consideration with fast powders such as Bullseye, no matter how light the charge is or how spacious the case.
The phenomena of Secondary Explosion Effect (SEE) is known to occur only with the slow powders at very low loading densities. Precious little is known about the mechanics of the phenomenon and it is not even known if the expression, Secondary Explosion Effect, is accurate. SEE, despite best efforts of the leading powder companies, cannot be reproduced in the lab, at least in the literature that I have been able to find. Some of the powder companies now are putting notations in their manuals not to reduce CERTAIN loads below 80% loading density. One should note that such notations are for a very limited number of powders and cartridges, such as W-W 296 in the .44 Magnum. Actual documented SEE cases were at densities much less than 80% and with slow powders.
Cast bullet shooters discovered SEE while experimenting with some of the very slow powders. However, they have been using moderate speed powders at much reduced loads since the days of Dr. Mann, with no untoward results. Only the very slow powders exhibit SEE, usually those that were developed for the .50 BMG and magnum rifles such as MR-8700, etc. Recent events posted by Charlie Sharps, "Charles J. Sharps Ph.D" indicates that any powder that is SLOW FOR THAT PARTICULAR APPLICATION, loaded to a significantly reduced powder density, might be suspect. His was a Hercules 2400, .45-70 Contender blowup.
If SEE were a real danger with other than very slow powders, we would have MANY gun blow-ups. Think about it a minute. The .38 Special case uses only about 20 - 30% of its case volume when loaded with typical target loads. Anyone seen a .38 go high order from a (true) target load? Cast bullet shooters fire millions of rounds each year using VERY low loading densities in most cases.
If that is not enough, the ultra-lite loads have been experimented with for a good many years, where a typical powder charge might be 2-3 grains of Bullseye, 700X, Unique, or any faster pistol powder in a .30-06 or .45-70 case. If SEE were a realizable phenomena for fast powders at greatly reduced loading densities, this would certainly have resulted in many blow-ups. These ultra-lite loads are not isolated uses as the NRA has written them of them over the years, at least as far back as 1967 (NRA Handloaders Guide, Pg. 154). Reloaders, unfortunately, ascribe some anomalies to conditions other than the actual causes. Several other things that can happen to increase pressures:
1. Excessively thick case neck thickness due to reforming procedures or metal flow - causes over-diameter cartridge neck. Jamming the large cartridge neck into a tight chamber neck is a very good recipe for disaster.
2. Build-up of residue in the neck area of the chamber which compounds 1, above. Cast bullet shooters have experienced this from lube build-up.
3. Stretching of case length resulting from both firing and drawing the expander button back thorough the neck during resizing - causes the mouth of the case to jam into the corresponding chamber area and impede bullet release.
4. Significant increase in local ambient temperature over that in which the load was developed. This can have more effect than the unwary may suspect.
5. Changing to another lot or manufacturer of brass that has a smaller internal volume. This is usually a hazard only if maximum loads for the gun were developed using larger internal volume brass.
6. Bullet seated to a greater overall length (OAL) so that bullet is forced into rifling when the action is closed. This is, of itself, not a hazard; many of my cartridges are prepared using this technique. However, if the load was developed with the bullet seated to normal factory load OAL, that same powder charge can be excessive when the bullet is seated so that it touches the lands.
7. A change of bullet ogive so that the effect of 6 is realized even though cartridge OAL remains the same. I have found at least two boxes of .22 caliber bullets that had noticeably different ogives in the same box.
8. Change to another lot of powder that is faster albeit of the same manufacturer and type.
9. Excessive headspace (or too short cartridges) which can result in head separation and allow hot gasses and molten metal to blow back in the shooter's face. This is not necessarily a pressure excursion, but that is often blamed as the problem.
10. Excessive powder charge. Reloaders are usually not willing to admit this possibility, but we all make mistakes. About 100 years ago, on the second box of .38 Specials that I ever loaded, the charges were so excessive that the web my poor wife's hand was split open. The gun held together and so has our marriage (five kids).
Of these causes, I have found numbers 3 and 10 to be the most common cause of pressure excursions.
SEE is a very real phenomena, but it is blamed many times when the shooter has, in fact, allowed one or more of the above conditions to occur. For those who care to investigate further, back issues of The Cast Bullet have a number of articles discussing same. Handloader has also treated the subject a few times.
SEE is a real phenomena, but, I suspect, not as prevalent as rumors would indicate.
Norm
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