How important do you all believe it is to deburr the flash hole? Can you actually tell a difference in accuracy?

I debur all omy brass as I continue to load it.
I tried an experiment with 257 Roberts and fired both deburred and straight factory brass. There seemed to be a very slight trend toward more consistent results (velocity, MAD, SD.
I wish I had had the shootoff on 22 Hornet brass, but deburred it all before considering a shootoff!
As near as my educated fingers can tell, 22 Hornet has the biggest and most consitent (almost every round) burs in any I have deburred. So far I have done 22H, 257 Rberts, 30-30 (several different brands, 357 Mag and Max, 44 Mag, 45-70.

Of all of these the heavy bur in the Hornet seems most likely to cause differences from shot to shot due to the "big" burs and small case capacity.
LouisB
I could be wrong though ; >

sll
i think it is a good routine to get into. I believe it is just a part of good brass prep. Plus the concept of keeping everything concentric
has to help make better more accurate loads
Dave

From my very limited experience in this field I honestly think that with best quality LAPUA, RWS, Norma etc that flash hole deburring could actualy INTRODUCE irregularities.

If you think about it from an engineering point of view, reaming out a hole by hand is not exactly precision. LAPUA brass for one has drilled flash holes so does it really need it?

1894,I think you're absolutely right, at least about Lapua.

Last weekend I was loading some new Norma brass in .222 and in about 25% of the cases you couldn't eyeball the flash-hole without seeing some obstruction. Not very good at all.

I'd always buy Lapua if I had the choice.

Patrick

I did a side by side comparison test with 50 rounds of 9mm. I found that there was a VERY noticeable difference between the rounds that had the primer flash holes uniformed as opposed to the rounds that were loaded with "stock" brass.

All 50 rounds were loaded with a 124g fmj bullet, a WSP primer, (as best I recall without going out to the shop look at the data) 5.1g of Unique and once fired S&B brass. The only difference was that 25 rounds had the flash hole uniformed with "Midway's" uniforming tool. All rounds were fired in 5 shot groups alternating batches, from 30 feet out. I even had my shooting buddy load my pistol for the last 4 targets so there wouldn't be any effect by me to prefer one batch of ammo over the other.

What I found was that the cartridges that were loaded with the flash holes uniformed had tighter groups 5 out of 5 times! As best I recall the smallest group size difference from the batch with flash hole uniformed to the batch without was well over a inch!

Well, that's what I've found. I now uniform every case that I load. But go and try my little experiment for yourself, just drill out the flash holes with a .085" drill bit and de-burr the hole with a 1/4" bit on a number of cases then load them with your favorite recipe!