Donuts in brass



  • I have never dealt with donuts but think I might have an issue with them now. My Lapua brass has 8 firings on it now, and has had no issues but this time around when I seated the bullets I felt a sliht resistance right before the bullet is fully seated. I haven’t turned the necks on this brass which is what I’ve heard caused donuts. How can I tell if that’s the problem and what can I do to fix it?



  • Running a bushing die? That's typically what causes donuts.

    FL sizing with expander doesn't make donuts.

    You can use a micrometer to measure brass thickness along the neck and should be able to measure a donut. Or, you can simply use a slip-fit cylindrical object to feel if there is a constriction down there at the neck/shoulder junction. Drill bit might work, depending on the diameter you're dealing with.

    You can ream a donut out... sort of... but annealing is needed for best results.

    Switching to a full length sizing die with expander/decapper left in will eliminate this from happening again.



  • @orkan I anneal after every firing but do use abushing die and expander mandrel after sizing I would have thought this would force any donut to the outside at least. If I full lenght sized at this point would it remove the donut or is it to late for that? Does this sound like a donut issue to you?



  • @bull81 Yes, it does sound like a donut issue. If it's seating hard right there at the neck/shoulder... it's usually what happens.

    The problem with the bushings is there is open space between the bushing and the die itself. That allows for material flow. Also, the bushings never seem to go all the way down to the neck/shoulder due to various factors. This allows that area of brass to get treated differently than the rest of the neck.

    The only bushing dies in my rack are those used for neck down operations on wildcats. All of my full time dies for production brass work are FL non-bushing dies. Either custom honed or off the shelf.

    I doubt that full length sizing them now would bring relief. Though it's certainly possible.

    To put things in perspective, I've put nearly 50 firings on a single piece of brass without annealing and using a FL die. It isn't as if over-working the brass is a thing when it pertains to good brass, match chambers, and good dies.



  • @orkan well damn that all makes perfect sense. I have a forester full lenght sizer but it won’t bump the shoulder back enough. I’m going tomorrow to run this load out to 1400 to get true dope. Guess that’s gonna be a waste of time now



  • Things like this is why I always recommend that before someone "settles in" on their process or load, they first grab 5 pieces of brass and see how many firings they get out of it and how the rifle behaves through those firings. This will sanity check the process and make sure you have staying power.



  • Got a cutter pilot on the way from K&M to try and remove the donuts, and a Whidden non bushing sizer die on the way too.



  • @bull81 Unfortunately, I doubt you're going to be happy with the results of the cutter and FL die. With a donut now formed, the FL die is going to push that donut in as it sizes all the way to the neck shoulder junction.



  • I concur with @tscustoms. Once the donut is formed, that brass will never be as consistent as brass without it.



  • That may very well be the case but I figured I’d give it a shot before scraping the brass. I went this morning and shot the 50 rounds I had loaded with no ill effects. I’ll post pictures later but managed to get a 6.75 inch 5 round group at 1682 yards with my 6.5x47. I’ve never shot that far in my life and am impressed with that performance



  • Figured I’d give an update on this. With the results I had at 1682 yards the other day I was wondering if I really even needed to try and remove the donuts and risk ruining 200 pieces of brass. I used the K&M donut cutter and removed the donuts out of 20 pieces to test, and then used the FL sizer and resized a few pieces fired the other day. After resizing I seated bullets in the cases and had no change in seating pressure. Looks like I may have caught it before it got to bad, I’m gonna load and shoot the remaining brass and hopefully they will react just like the others and smooth out after sizing. I’ll test the ones I cut later but am a little concerned about them because the had a little rough spot in the neck where the donut was cut out from.


Log in to reply