You're up again early.
I tend to agree with the benchresters on this issue. I don't DO it, I don't think any of my firearms are capable of delivering the added consistency - But making every component as uniform as possibly cannot possibly add a source of inconsistency. And accuracy is all about being consistent.
Most manufacturers punch the flash holes in the brass and this can leave a ridge and burr on the inside of the case. It can cause the flash from the primer to shoot to one side of the case and in some circumstances this can cause inconsistent ignition. In reality it doesn't do much in helping hunting loads. But for extreme accuracy it is one more procedure to add to your case prep list. In actual practice you will probably see (maybe) a .080" average increase in accuracy. It is normally left to the benchrest shooters and extreme accuracy varminters.
Having heard the same thing, I have always deburred new cases before loading them. I have never run any side by side tests so can't say that it helps or not. Guess I just have faith in those supposedly more astute than myself on this topic.
I do it to all my 'important' cases. Service Rifle, Tactical Rifle, the .338 all get their holes deburred. I don't do it to my high volume PD/sage rat stuff only because it's too much work.
Pick up a copy of Glenn Zediker's "Handloading for Competition", there's some pretty good info on brass prep. Most brass, except Lapua, has a punched primer hole. When the punch goes through, the displaced brass flows off to one side or the other. Deburring the hole removes the brass that was displaced, allowing for a more even 'flame' from the primer, and so even powder ignition, and so consistent pressures shot-to-shot.
Just one less thing to worry about.
Vibe, you might want to test your handloads- deburr some cases and compare their consistency (SD and MV). You might be surprised.
I deburr almost everything. Even the vaunted Lapua 6PPC brass is drilled with a high speed process and sometimes leaves a large burr. Flash hole deburring is probably the most inspection the inside of your case ever gets. I have found interesting things on occasion including a several inch long shaving curled up inside a 6BR case and wedged tightly. No idea how it got there but no question I am very glad I found it.
Deburring is a one time thing that might take fifteen-twenty seconds a case when you are rolling. That doesn't seem like a big deal to me for the very few cases that it will make a difference in, even for hunting accuracy. I cut a button out of several hundred Norma cases years ago. Every flash hole punched had left the button hanging. A few had pulled the button back and pretty much filled the flash hole. I had to push the button out of the hole from the primer side to get my tool in.
If it is more than plinking ammo I deburr. I also uniform primer pockets. I chamfer the mouth of the brass with a VLD angle tool. I may or may not trim to length before the first firing depending on the length of the case and chamber. I never square the face of my brass. It removes too much metal to do something that will be done when I fireform the brass anyway. If I cut away the brass when new I think it always leaves a thick and thin side. After fireforming and firing once or twice, I have touched the faces with a uniformer but found it to be a non-issue.
I deburr all my cases, and think it's worth the time. Especially when you see all the brass shavings left from a bag of brass. When you're trying to be as accurate as possible, while not benchrest, I think it is time well spent.
there is a way for you to answer your own question.....
stand a 100 cases straight up. Using a small flashlight look inside the cases at the flash hole....very interesting what you see at times.
Some lots of brass are better than others. In some, you will find very clean flash holes and in other lots you be amazed at how 1/3 of the cases seem to have the flash hole obstruced by a very large burr.
How much difference it makes in accuracy, I really can't say. The only thing that I can say is that knowing this fact, it really bugs me.
I deburr all brass with punched primer holes. Have not done it with Lapua yet. In fact, I just did a batch of 243 Saturday, took me about 1.5 hours to do 200, deburr, and chamfer neck ID/OD. I have a drill press, so I chuck the appropriate tool into the press and have at it. Years ago when I started doing load development for shooting High Power, I ran a test using 5.56 LC brass, and found that deburring the flash hole gave positive results, nearly 1/4 inch at 100yds. It was just 10 shots each, probably not even statistically significant, but it seemed to help a lot and was easy to do, so why not?
I used to deburr flash holes on every case. But, it's one of the things that I've just let fall by the wayside, as my free time has shriveled. As it is now, I've not deburred a flash hole for any brass for my last several custom rifles. Same for primer pocket uniforming (or even cleaning them...). Haven't weight sorted cases for a long-long time. Don't trim for length anymore either - except once after fireforming IF the cases are near chamber length (otherwise I literally do not trim, ever not even once).
Sounds bad, I know. Especially coming from someone who used to be fanatical about taking brass prep to the extreme for every rifle I owned. But, after giving up on most brass prep completely for lack of time, I've found that for my purposes, I've not been able to detect any difference. Not saying it doesn't make any difference. Only that for my rifles and how I use them, that whatever difference it might make, has not had any effect on the results I get (dead varmints).
I do still neck turn every case for every rifle though...
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