Educational Zone #152 – Does Polishing Media in Flash Holes Affect Accuracy?

Like a lot of reloaders, I like to polish my brass before loading it again. It is possible to use a system of wet polishing with stainless steel media for a really bright shine. I will post about that soon.

But for many of us, we use vibrator polishers with either crushed walnut shells or corn cob media to shine our brass.

I have used several types of media through the years, and some work better than others. Walnut shells will be very aggressive at removing dirt or other fouling. But normal brass will be shined brighter by using corn cob media and a little brass polisher.

At one time I used to use Brasso in my media, but read that it could cause damage to the brass.

I tried brass polishers sold by different folks and had some success.

But recently I have been using a little (about a cap full) NuFinish Car Polish in my media and it works great.

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I’ve seen corn cob media for sale from big reloading companies for as much as $2.50 per pound.

I found that Grainger’s carries corn cob media which comes in a 40 pound bag for around $30.

That’s about 75 cents a pound.

It works great.

Just be sure to ask for “1420 Corn Cob media”.

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I use two vibrating tumblers.

I use the blue one from Midway to remove the sizing lube, and then the orange one from Lyman for the shiny polishing.

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I cleaned some .223 brass that I had shot.

Here’s what it looked like after resizing and before cleaning.

Here’s what it looked like after resizing and before cleaning.

Then I put it in the tumbler and let it do its thing for about 8 hours.

After the brass is shiny enough, I pour the brass and media into a box I built to separate the two.

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Here is what it looks like when it is finished.

Here is what it looks like when it is finished.

When shining rifle brass, I resize and deprime before polishing.

This can result in the media getting stuck in some of the primer flash holes.

I pick up a couple of pieces of brass at a time, and look at the flash hole to see if it has media in it.

If so, I use an ice pick to punch it out.

This doesn’t take very long.

Continued below...

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Here's what it looks like when the corn cob media is stuck in the flash hole.

Here’s what it looks like when the corn cob media is stuck in the flash hole.

However, I’ve often wondered if I missed one, would it actually show up in reduced accuracy?

One way to find out.

I looked in the flash holes and separated the brass into two groups, one with clear flash holes, and one with media stuck in the flash hole.

I then primed both sets of brass and kept them separated.

But I loaded them with identical powder charges and identical bullets (The excellent Sierra 52 grain BTHP #1410M)

I will shoot them into separate groups and compare the results.

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Here’s my new Savage .223 bolt action rifle.

Here’s my new Savage .223 bolt action rifle.

What do you think will happen?

I tried to shoot slowly and let the barrel cool.

It was a little windy, but too bad.

All groups were shot at 100 yards.

All are 5 shot groups, and any that seem to have less that 5 shots mean two bullets went through the same hole.

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Here are the results of this limited experiment.

Here are the results of this limited experiment. Groups #1.

The “clear flash hole” group is on the left and the “plugged flash hole” group is on the right.

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Groups #2.

Groups #3.

Groups #3.

Conclusions:

That’s right folks, there seems to be no difference at all.

In fact, it might even look like the rounds with the media in the flash hole were slightly “better”.

Take another look at this last group, at 100 yards.

I believe I might have found a load this rifle really likes.

The Sierra 52 grain BTHP, some AA-2460 powder, and corn cob media in the flash hole. (Just kidding about the media.)

I will probably still clean out any media in the flash holes, but if I miss one, it doesn’t look like it will make a bit of difference.

And to paraphrase Forrest Gump, “Shooting is like a box o’ chocolates, you never know what you’re gonna get.”

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A word of caution: Don’t “over-learn” from this test.

“This media” in “this brass”, with “these primers” had “these results”. Different media (such as walnut hulls) or other variables might make a difference. Use caution when reloading. And clean those primer flash holes.

1 Comment on Educational Zone #152 – Does Polishing Media in Flash Holes Affect Accuracy?

  1. So, you’re the one having all the fun. Excellent website and research–I’m jealous, well sort of, about the gun and ammo profession and hobby you’ve worked to create. I have advanced much more efficiently in the sport of shooting since I’ve been reading on your site.
    .
    Great way to relax after working with clients on the water all day.
    Thank You sir.

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