Danger in below minimum powder loads?

[Grendel-Gene]

I seem to have read on occasion that not putting in enough powder in the case can also be dangerous.... But I have never really understood why.

Can someone here please explain it to me?

I am especially concerned since i am currently fire forming AK Brass to Grendel (although i have been using 25 grains of BLC (2) to do this without any problems so far)...

Anyway, better safe than sorry!

Again thanks.

GENE

[Michael]

Only thing I can think of is getting a bullet stuck in the barrel?

Hopefuly someone smarter/more experinced than me will weigh in.

[ricsmall]

michael is right. the projo can get stuck, resulting in the gas going the only way it can;backwards. I dont know what it would do in a semi auto, but in a bolt gun it can be catastrophic. I wouldnt want to find out.

[stokesrj]

It has been observed that in some cases, usually straight walled pistol calibers, that it is possible to achieve detention isteasd o a consistent gradual build up of pressure. The only explanation I have read is that the case laying horizontally with a half charge offers more surface area to the primer, which in turn produces a very sharp pressure spike. I've never seen this personally but I've read of it happening a few times over a period of 40 years.
Bob

[StoneTower]

I too have read about the danger of light loads a few times too. Being that it happens so rarely one also has to ask if it could be a double charge light load that is actually causing the problem. My father use to load a 30 Newton with a light load of 2400 pistol powder and a very light 30 caliber bullet to shoot some type of grouse (which they called partridge) that would sit in the trees when he hunted moose in the 1960's. The birds would sit in the tree until they were all shot one after another. My dad said that you had to aim 2 inches high and it would take their head right off. He stressed the importance of tipping the rifle muzzle up before discharging the round to ensure that the power column is in contact with the priming hole. A double charge of pistol powder could easily cause a pressure problem in a rifle case and easily go unnoticed while loading due to the very small volume of powder.

It has been observed that in some cases, usually straight walled pistol calibers, that it is possible to achieve detention isteasd o a consistent gradual build up of pressure. The only explanation I have read is that the case laying horizontally with a half charge offers more surface area to the primer, which in turn produces a very sharp pressure spike. I've never seen this personally but I've read of it happening a few times over a period of 40 years.
Bob

[Drifter]

As stokesrj alluded to, reduced loads can potentially result in powder detonation instead of powder burn. Can be very dangerous.

Explore "secondary explosion effect" on the 'net for various theories.

[Von Gruff]

It has to be understood that the powder burn rate also has an effect. Some powders are not position sensative and a light charge can be safely loaded with no concern.
As an example I use Red dot in some of my greatly reduced loads in 7x57 and 404 Jeffery. The Jeffery safely takes 84gn H4350 behing a 400gn bullet for 2335fps but I can also load 63gn of H4350 for just 1900fps as it is still over the 65%load density minimum I feel is safe for that powder. I load just 21gn of Red Dot for 1500fps and this is a very small amount in the large Jeffery case but because it is a non position sensative powder is completely safe. I have even used this load on the hill amongst a mob of goats.
The 7x57 which has a load in the 46-50gn H4350 safely runs 39gn with my hunting cast bullet at 2415fps but a plinker load at 1500fps is only 11.5gn Red Dot.
Some powders need a filler over the powder to keep them against the primer as the problem with slow powders is that they are intended to be colum burnt as in the case full or nearly full so that the flame front is only the case diameter wide. The problem comes about when a light load lays along the length of the case as noted above, and offers a larger surface area for the flame than is intended and causes a pressure spike that can be disasterous.
Safe loading practices include knowing the safe load density minimum for the case and powder you are loading and unless I know for certain ( as in documented by the manufacturer or other experienced handloaders have documented a minimum density in numerous sources, I am reluctant to reduce charges below minimum start loads.

[Bwild97]

It has been observed that in some cases, usually straight walled pistol calibers, that it is possible to achieve detention isteasd o a consistent gradual build up of pressure. The only explanation I have read is that the case laying horizontally with a half charge offers more surface area to the primer, which in turn produces a very sharp pressure spike. I've never seen this personally but I've read of it happening a few times over a period of 40 years.
Bob

As stokesrj alluded to, reduced loads can potentially result in powder detonation instead of powder burn. Can be very dangerous.

Explore "secondary explosion effect" on the 'net for various theories.

The situation that Stokesrj and Drifter are referring to is a very specific situation involving the .44 Rem Mag, H110 pistol powder and a "300g XTP IIRC", where the individual was attempting to develop a sub-sonic "light recoiling" load for his revolver. I remember finding that article in search of data using H110 in my Glock 20, 10mm handloads. I'll try to dig up that article and post it here, it is a very interesting read.

[P-P]

In many powders it is not too much of a problem, but in certain powders such as H110 and Win 296 the detonation problem is GREAT if you drop below 3 - 5% less than published minimum loads.

[mlmiller1]

This discussion is very interesting to me as a theory & maybe it has been proven to be correct with some powders however, I would like to point out the cowboy action shooting game & how those folks use the tiniest bit of powder they can measure to get their little bitty bullets just barely moving. Most of those guys load tiny, way below book powder charges & don't use a filler to keep the powder at the primer end. They also have large case volumes with calibers originally designed for black powder now holding smokeless charges. I am certainly NOT saying to load really light charges, I'm just pointing out a very, very large number of folks that do load WAY low, small volume charges.

My advice is to use book loads, stay in tolerance until you are willing to blow yourself up. Every time you load something out of book, either low or high, you are walking a dangerous path. Tread carefully or walk the well trodden path of tested by scientific equipment book loads.

MLM

[P-P]

mlmiller1 you are correct... it doesn't seem to apply to the really fast burning powders like red dot, unique, etc.

[rasp65]

It is a rare and unusual phenomenon. Either P.O.Ackley or Julian Hatcher described in their books the potential danger of using reduced charges of slow burning rifle powder in rifle cartridges. However they were unable to reproduce the detonation of the powder in their experiments.

[jawbone]

explosive reciprocity detonation under certain squib conditions. if i can remember correctly, jacketed bullets instead of lead cast bullets aggravate the situation.