Flash hole deburring

**DesertDug** · 03-07-2019, 03:58 PM

How important of a step is deburring case flash holes? Does this improve groups?

I have never done it in my short history of reloading, do I need to start if chasing groups?

**kurusty** · 03-07-2019, 04:12 PM

I only do it once, then never check them again. This is only for my target/precision ammo, not fun stuff. I'm not an expert, just my opinion for what works for me..

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**DesertDug** · 03-07-2019, 04:14 PM

Ya, as I understand, it is a one and done type of thing.

**kurusty** · 03-07-2019, 04:19 PM

I'm sure that if you ask bench rest shooters, you'll get a different answer

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**CFJunkie** · 03-07-2019, 04:22 PM

DesertDug,

It depsnds upon how the brass was manufactured and how the flash hole are formed.

Some of the cheap brass I used when I first started reloading had burrs and I trimmed those, mostly because people said it would help.

Honestly, when I was still using cheap brass, I probably wasn't shooting accurately enough to notice any difference.
My technique variations were masking a lot of reloading variations so I never noticed a difference.

I don't bother now because I use Lapua brass and I've never seen burrs on their flash holes.
Apparently, they form the flash holes without creating burrs.
But now that I learned much better technique, both in shooting and in reloading, I am shooting Lapua brass exclusively and I don't need to worry about flash hole burrs.

Does it make a difference in accuracy?

The only really accurate rifle that I shoot both Lapua and Federal brass in is my Les Baer Super Varmint .223.
I see very little difference in accuracy due to brass but the Federal Brass doesn't last as long as the Lapua.
I have gotten out of the habit of cleaning up flash hole burrs and I don't do it with the Federal brass.
But the results say it makes very little difference in accuracy, if any.
Then again, I still might not be shooting accurately enough to see the difference.

**mudpig** · 03-07-2019, 05:08 PM

I haven't kept detailed logs, but I believe that deburring the flash holes help with my ES/SD numbers. Some loads I've got with the extra work done have ES in the single digits.

**DesertDug** · 03-07-2019, 05:35 PM

Originally Posted by CFJunkie

DesertDug,

Honestly, when I was still using cheap brass, I probably wasn't shooting accurately enough to notice any difference.
My technique variations were masking a lot of reloading variations so I never noticed a difference.

I resemble that remark.

**Stumpkiller** · 03-07-2019, 10:50 PM

How important? Not very. But maybe the difference between first and second place.

Accuracy improvements are cumulative. And it is one of the easier things to do.

**DesertDug** · 03-07-2019, 11:04 PM

[QUOTE=Stumpkiller;451348

Accuracy improvements are cumulative. And it is one of the easier things to do.[/QUOTE]

Great statement!

**243winxb** · 03-08-2019, 11:42 AM

Better to do than not, with cheap punched spit holes. Done with a Lyman tool. There are better tools availabe.

**darkker** · 03-08-2019, 02:16 PM

As said by several, it's a nuance detail. Sounds like you aren't in the running for the PRS championship, so I personally wouldn't monkey with it unless you find yourself with Floridian brass and hanging chads

I personally don't with any of my brass. Years back I started testing a 308 that I began enlarging the flash hole on(came from some very old testing done on the 45-70 cases). With the amount I was playing with, the "difference" was statistically just noise on the pressure testing. So while maybe a technical difference, probably not real; at least on the 308.

**Robinhood** · 03-08-2019, 02:58 PM

2 things. Make sure your pilot is not larger than the flash hole. Do not go any deeper than a very small chamfer.

performance and consistency has bee negatively effected by the wrong tool for the job and being overzealous. Don't ask me how I know. Biged can probably do the topic a favor.

At 800 and beyond you start to see your shortcomings. Hitting steel no problem hitting X's (1/2MOA) is a little tougher. Hitting golf balls even tougher.

As far as chasing groups.... for longer range success, properly full length sized cases of the same lot and manufacturer, uniformed flash holes and properly seated primers, **uniform** neck tension on your brass, imho an exact weighed powder charge. Low bullet run out. A chrono is a good idea for at least a couple of reasons, for long range a it is a must. There are guys that use range brass without annealing, different bullets, mix powder and use a Hornady powder thrower without weighing, for .020" groups at 1000 yards. I have not met any of them but there there. Wait.......

**celltech** · 03-08-2019, 04:10 PM

Thanks guys...now I had to order yet another tool...lol

**darkker** · 03-08-2019, 04:34 PM

Originally Posted by Robinhood

There are guys that use range brass without annealing, different bullets... and use a powder thrower without weighing, for groups at 1000 yards. I have not met any of them but there there.

I'm certainly not 0.02" groups at 1K, but can hold moa or a little better at times.

I don't use "range brass"(I'm the only one there), but absolutely mix headstamps, some bullets; and don't weigh my powder charges.
Definitely agree that consistency is the real key to all of it.

**PhilC** · 03-09-2019, 12:46 PM

I've had a K&M uniformer for very long time, use it once and done. It has a fixed shoulder so you can't go too deep. The current version of their uniformer is much nicer than mine, but the cutter head is still same.