Originally Posted by Chas1
Are we sure they're drilled as I came across the link below albeit a couple of years ago but, talks about a mandrel see post #7. Maybe they drill them now???
De-burr Lapua flash hole?
This one we can take care of; Lapua flash holes are punched, not drilled. They have been for nearly ten years now. Good results can be had with either process, as long as it's done correctly. Otherwise, you can have problems with either method. In our case (no pun intended) we found that a properly supported punch gave better results than drilling, which had a tendency to produce eccentric flash holes. This occured when the drill walked or wandered slightly during the process, leaving a slightly eccentric (oval) flash hole.
Flash hole size has already been discussed, and the smaller size we use has shown consistently improved accuracy in almost all cases. Obviously, we don't recommend enlarging them, as we would expect to see a resultant loss of accuracy potential. Deburring . . . if you want to, and use a tool that doesn't open up the case's flash hole, knock yourself out. I've done it, and frankly, I'm sure it amounts to a good many hours of my life that I'll never get back. Never saw that it made much difference, but was more a matter of adjusting headspace. That is, the space between my own ears and the satisfaction of knowing I'd done something extra. I'm just as susceptable as anyone to buying tools or gadgets because they're sharp and shiney, and I don't have that one. And I've got the reloading bench and cluttered drawers to prove it. I've seen some seriously bad cases over the years, and in some of these the deburring might have been worthwhile. However, if you're using cases that are that bad to begin with, you probably aren't shooting for extreme accuracy anyway. In cases where quality brass is being used to begin with, it's most likely a waste of time. Benchrest shooters may argue this, but then again they do any number of things that are completely pointless for most other shooting disciplines, including many other highly demanding competitive disciplines.
Bottom line here;
One, do it if you want to, but take pains not
to enlarge the flash holes, and two, don't
expect to see any noticable increase in accuracy when you're done. If it makes you feel better and adjusts your headspace a bit, that's enough. That, and it IS and excuse to buy another tool!