Speer 357sig small flash hole

[shu]

Have not reloaded 357sig much nor recently, mostly being limited by brass. To get back into the 357sig, I purchased a quantity of once-fired Speer from Brassman. Starting to work on this, I find the de-priming pin of my RCBS forming die kept pulling out.

Seems the flash-holes of this Speer brass are small relative to other cases using standard primers - certainly small relative to the de-priming pin.

There is probably a way around this problem - working the diameter of the pin down with some emery cloth, maybe. (That would of course leave the pin thinner and weaker; maybe replacements can be made from old drill bits.)

But I got to wondering ........ why the smaller flash hole? and how will it affect my reloads. I favor BlueDot, a relatively slow burning powder for the 357sig. It takes a case full.

Did Speer design the factory load using a lesser quantity of a faster powder? That would keep the cost of production down, but faster powder would have an earlier peak pressure. Perhaps the smaller flash hole retards ignition and delays timing of the pressure peak. End result, Speer cuts production costs but creates a problem for reloaders.

Any thoughts or experience with this?

 

[ReloaderFred]

You're going to find that there are two different size flashholes in Speer brass. I was once told that about half of their 357 Sig brass is made by another company, perhaps Starline. You can tell the difference between the two lots before you even deprime it by the look of the base. Some of the bases are flat, with sharp markings and some are kind of rounded towards the primer pocket.

The experts tell me the size of the flash hole doesn't affect the burn rate or accuracy, and I haven't been able to tell any difference myself on the target or over the chronograph. This has also proven to be the case in .45 acp, with the very large flash holes now being used with the non-toxic primers, to keep them from backing out of the primer pocket when fired.

You'll find that if you try to deprime the small flash hole brass with a Dillon die, you can't. Dillon uses a decapping pin with an even thicker diameter than RCBS.

I've got about 10,000 rounds of Speer brass in 357 Sig, and about half of it is the smaller flash hole. I use a Lyman die, with it's smaller decapping pin, to deprime the brass with the smaller flash hole. I've set up a process for drilling out the small flash holes really fast, and I've converted all the small flash holes to "standard", and since it only has to be done once, it saves me the headache of separating the brass the second time around, etc.

If you measure the flash holes of various brands of brass, from all around the world, you'll find various sizes, which don't make much difference for the average shooter. Brass from foreign manufacturers use metric measurements, and U. S. manufacturers use inch measurements, so you have variations right there.

But back to the Speer brass. It's just two different lots of brass, with two different sizes of flash holes, and probably using the same powder and getting the same ballistics. The bottom line is, don't worry about the why, just use it.

Hope this helps.

Fred

 

[shu]

Much appreciate. One less thing to wonder and worry over. Picked up a unimat (small tabletop lathe) from my father (r.i.p). May just chuck up a drill bit, put on a stout glove, and try to bore those bad boys out.

-shu

 

[ReloaderFred]

I've also got an Uni-Mat Lathe, but that will be pretty slow. I've made a stand for an electric drill that mounts the drill so the chuck is facing me when it's clamped to the bench. The drill bit will be parallel to the floor. I put a drill in the chuck and use the rubber coated gloves they sell in hardware stores that look like mesh, dipped in latex, and hold 3 or 4 cases at a time and drill them out pretty quickly. I use a # 47 drill (.078"), and the sharper the drill bit, the faster it will go. The rubber coated gloves are thin enough to allow you to work in them and the rubber gives enough grip on the case to keep it from spinning.

The key is making the drill stand and making it rigid enough that there won't be any play in it. I made mine out of about 3" of plywood glued together, making a wooden pedestal about 3"x3"x4". I then drilled it to match the contour of the back of the drill. Then I drilled a series of connecting holes to make a slot under the contour, all the way through the block, so I could put a large metal hose clamp through it to hold the drill in place. The whole thing is attached to a piece of plywood about 10" square that I clamp to my bench when I need it. It's really simple to make and holds the drill about 3-4" off the bench, which makes it a little over waist high for me.

I also use this same setup to clean primer pockets, but with a brush in the chuck. I can hold 6 or 7 cases at a time and just touch them to the brush and they're clean.
Hope this helps.

Fred