Monday, May 14, 2012

Happy Monday!

Two more weeks with students, and then another week shoveling paper for the tie creeps. I think I shall give them the blessings of my resignation soon, as they have asked. I very strongly suspect they intend to hang my partner out to dry, giving him only an unqualified 'aid' next year instead of another instructor. That's what they have done in another shop this year, and they see a way to cut $$$$ doing so. The students education can go to hell I guess.

On the down side, I'm going to miss some of those kids when it all ends.

On the up side, I'll soon have a new set of challenges... which I am already bringing up to speed. As a result.... I'm booked with something just about every day til the end of June. I am so very much ready for this, even if it means leaving the loving bosom of the modern education indu$try. Yes.... seven day weeks are a bit of a stretch for a man of my ... um... advancing years.

Still, I find time to relax, do some shooting, and pursue my interests. One must feed the soul, you know! Here are the results of last nights bench time:

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Carteach is in the process of load development for Liberty, the M1 Garand. This entails shooting... lots and lots of shooting... but that's only part of the happiness. It also requires lots of hours blissfully spent at the reloading bench.

Part of the process involves case preparation. On this topic, books have been written... but not by The Fat Man. Here, just one small topic is being addressed.

In choosing which cases to run the load development with, the entire 30-06 inventory in play. That means over 1000 cases of different date and manufacture. Amongst them, a fair number of military casings.

The thing is, there is a 'Given' in the reloading world. It's been engraved in stone for so many generations that it's accepted as a golden rule. That is: Military brass is thicker and heavier than commercial brass. That means the interior volume of the case is smaller, so therefor the charge weight must be lowered or excessive pressures will result.

But.... is this rule so golden?

Today Carteach took a bullet for the team, and weighed several hundred cases, both commercial and military. The results were unexpected.

The bulk of the cases were divided into three major types. Greek HXP, Lake City, and Commercial Remington and/or Federal.

Here's the unusual part.... on average, the commercial brass was heavier than all the military. Both Lake City and the commercial were heavier than the Greek HXP military. This indicates the HXP does not have a smaller internal volume, but in fact has a larger one. This changes the whole ball game when loading with the Greek HXP brass.

That chart below shows a clearer picture of what was found:

Now, I know this isn't exactly going to be wildly interesting for those not deep into the intricacies of hand loading.... but for those us who share that particular addiction, it's fascinating.

3 comments:

Old NFO said...

The amount of variance is ALSO interesting!!!

Hat Trick said...

How do you know that the variation of density of the brass might not account for the difference in total case weight from the various sources?

I'm assuming you've already decapped those cases. The procedure I've seen to determine case volume (actually a measurement that corresponds to case volume) is to weigh the empty case then dip the case in a bucket of water and carefully weigh the case filled with water. The difference between empty and filled is the weight of the water required to fill the case and indicates the relative volume.

Something else that would be interesting would be to section the cases and compare the internal structure and the thickness of the bases.

If you'd like to bypass all of this I have a stock of military match brass in .30-06 that was a hand me down from one of my mentors in CMP shooting. He had it left over from his days on the Army team. It's up at the farm so I won't be able to get to it until Saturday. I don't have an M1 Garand currently so I might let go of some of it. (I have ambitions of acquiring an M1 Garand again or I'd sell all of it.)
The match brass would give you a consistent lot to use to work up loads without worrying about variance in the brass.

Carteach said...

The idea of metal density never occurred to me. Interesting idea. I don't know if it would account for the wide variations, but it could certainly be a factor.

Yes, I would be interested in a batch of match brass.