"Problems with Light Loads"

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"Problems with Light Loads"

Postby wildcatter » Fri Apr 16, 2010 3:16 am

I have been asked about my post about light loads enough to make this a priority and to repost the thoughts under a separate category, then I'll include some additional data, here goes..


Quote:

15APR10

Hoot-Man and everybody else, if you're going to duplicate the factory loads, I assume that's going to be with 296, cause the 297 that Hornady uses, is more difficult to obtain. What ever you do, keep the pressures up with WW296/H110. I just surveyed the results of an induced Detonation, from a light charge of 296. The detonated round was a 25% undercharge round. This is a well known happenstance with light loads, especially with 269/110. Don't worry about 296/110 it is a great powder and I recommend them and love them, just don't experiment with light loads, unless you know what you're doing. We'll talk later about what you can and cannot do with reduced loads later. I just wanted to get this warning out.

Here's the problem, I maintain that the factory loads are mild at best, if you try to start out much under the factory loading, you're setting yourself up for an Ops. If your loads have progressed enough to stop ejection or are trying to rip off the rims, that's not usually because the load is hot, it's more of a function, that the bolt is trying to open to soon, well before the case has released from the chamber and this because of the Dissipater Gas Block position. So, start out with the factory loading and don't reduce much at all.

For more info, Google, "under loaded ammunition and detonation" or something like this.

..t

End Quote:

Hoot knew all about this malady, but many do not, so for more reading I did Google "light load detonation" and hit a ton of Data pertinent to your knowledge and is a good starting point. I particularly thought this would be good reading, http://www.charm.net/~kmarsh/burn.html . But much can be learned by studying this Phenomenon.

_________________________

Now, because many are wanting to develop "Plinking Loads", lets start a dialog about "Detonation and Light Loads".

What do you know about them and and this effect.
How do we prevent them.
Experiences with them.
Experiences with the aftermath of a Detonation.
etc.

There are many thoughts that ought to be explored here and we should.

..t
Safety First..t
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Re: "Problems with Light Loads"

Postby wildcatter » Fri Apr 16, 2010 4:11 am

I've used various fillers to keep the powder against the primer, to effect a good burn with a light load. I've used Dacron fillers from my pillow, to Cream-of-Wheat, to fill the case up to the bullet. Some of that might not be safe, so before you try this you might want to read the following. http://www.davidscottharper.com/shoot/ClaysAndGrits.htm

Why do this at all?

Let's see, because I just two days ago, surveyed the after effects of an induced Light Load-Detonation Event.

And because, many here want to develop so called, plinking loads, for their 450. Something that can be done, but extreme caution must be observed. So, Let us increase our knowledge-base, in this matter.

In my earlier years, I used to shoot very light loads, of slow burning powder, in a 44spl and on occasion I'd get a Squib Load. Click/Pop, and the primer would drive the bullet down the barrel a short distance and stop. Upon examination, the powder would be caked in a solid clump to the base of the bullet, probably from the pressure wave from the primer. It would take a knife and considerable scraping to dislodge the powder clump from the bottom of the bullet. I saw this many times and was a pain to drive the bullet out of a revolver.

After the bullet had stopped, what would have happened, if a burning ember, from the primer had then ignited the powder, with the bullet stopped? Ka-Boom, Detonation. The effect would be exactly, as if I'd have gotten with a bullet stuck in the barrel and fired another round right behind it. Ops. Ka-Boom! Now, that is an effect of Detonation. The Detonation Gods must have been protecting me, in those days, as a Cheechako.

The same can happen if you start the powder out at the front of the case, up against the bullet and then slowly raise the barrel, so the powder is still against the bullet and then set off the primer. You might see, Ka-Boom, a Detonation Event here too.

Or how about if a light load that is spread out over the bottom of the case in a horizontal barrel/chamber, like with an off-hand shot, and the primer blast spreads out over the top of the powder without igniting it? The primer will push the bullet to a stop somewhere down the barrel and after it stops, the powder might ignite from a left over burning ember from the primer ignition, at that point, Ka-Boom, Detonation!

Now I know these are just stories, with no scientific data, but if I were to bore you, you might not study the effect, so the stories should be taken seriously. The science will come as we examine the effects.

What are your stories, comments and data about this subject?

..t
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Re: "Problems with Light Loads"

Postby bushmeister » Fri Apr 16, 2010 8:30 pm

wildcatter wrote:I've used various fillers to keep the powder against the primer, to effect a good burn with a light load. I've used Dacron fillers from my pillow, to Cream-of-Wheat, to fill the case up to the bullet.
..t

Don't use dacron, the trimer out of that stuff aint good for you. in jest, but yet seriously. My mom always said Cream of Wheat WAS good for me, so I'll give it the nod ;)
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Re: "Problems with Light Loads"

Postby wildcatter » Fri Apr 16, 2010 10:56 pm

bushmeister wrote:
wildcatter wrote:I've used various fillers to keep the powder against the primer, to effect a good burn with a light load. I've used Dacron fillers from my pillow, to Cream-of-Wheat, to fill the case up to the bullet.
..t

Don't use dacron, the trimer out of that stuff aint good for you. in jest, but yet seriously. My mom always said Cream of Wheat WAS good for me, so I'll give it the nod ;)


Ok, Mark, but the more I study this the more I'm not sure about anything but near max loads. The Cream-of-Wheat thing has served me well, Buuttt. I only hope it serves you well, too.

..t
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Re: "Problems with Light Loads"

Postby pitted bore » Sat Apr 17, 2010 8:53 pm

T-
Thanks for the link to the Ken Marsh page. It seems a nice summary of the problem, and it fits with my own perception of the problems I've had developing a load with a 185-grain bullet in the 450B.

Too-light bullets can result in a light load. In the 450B its possible to make a light load with plenty of powder, but not enough bullet weight. I think this happens because a light bullet does not have enough inertia to oppose the primers detonation. The bullet is shoved out of the case by the force of the primer, which suddenly increases the effective case volume, making the load too light, even though the powder may have completely filled the case with the bullet seated. The powder begins to burn, but cannot generate sufficient pressure for a "good" burn.

With the straight case of the 450B, the powder that is not ignited immediately is positioned at the front of the case. From my limited experience, it seems that this extra powder may simply act a a load of cornmeal, and get blown out of the case right behind the bullet. This is probably OK, as long as the powder doesn't detonate.

In some of the work from last June, I got some hangfires, which disappeared with an increase in powder charge. As Ken Marsh noted, these can be an indication of possible read trouble.

I'll try to add some additional experiences later.

--Bob
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Re: "Problems with Light Loads"

Postby finnlndr » Mon Apr 19, 2010 6:25 pm

I highly recomend that EVERYONE read and understand Tim's point. I have experienced an inverse pressure wave and it ain't pretty. Protect and store your powder and primers properly. Be very careful with light loads. The main "smith at Williams told me a story about a guy working up a load with bullseye for his 30-06.(very little powder, very big case) The inverse pressure wave blew the back out of a model 700. He survived.
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Re: "Problems with Light Loads"

Postby finnlndr » Mon Apr 19, 2010 6:44 pm

There is one more point I want to make. For all of us reloading on a progressive for the 450/45pro, you will notice a big charge as the powder overflows the case. BUT when you are really putting them out and are in the groove, would you notice a powder bridge in your powder vessel, and a short drop because of it? So when loading 95% loads, you can still have a problem with light loads. I, for one, will now ALWAYS check that case when I place that 230 on top.
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