Bullet Runout

  • I'm back at it again.
    If you all recall I was having all sorts of difficulties eliminating runout when I was sizing my brass. After some trial and error I managed to resolve it by opening the neck on the sizing die.

    Now I'm having problems with runout when I'm seating bullets. Using a case that has very low or no appreciable runout, I'm seeing runout on the bullet (halfway between the tip and bearing surface) to the tune of 3-4 thou.

    I'm using a Forster micrometer seating die. Forster press. Lapua brass. 175 SMKs.

    I really have no idea what would fix this. I'd appreciate any ideas where to start.

  • If you are experiencing a problem (runout) from two different operations (dies) try analyzing the common symptoms (press, shell holder, etc.) for potential causes.

    "You are only as good as your tools."

  • @lathoto

    Thanks for the reply.

    Just to clarify I’m only having issues with one operation, seating bullets, with one cartridge. I’m able to produce concentric ammo otherwise.

    My previous issue was that I was oversizing the necks. By reducing the amount of sizing I fixed the problem.

    My problem is I’m not sure what to do to fix this, short of trying to find a better seating stem, but that seems like a shot in the dark. I know it’s not a press issue, so that leaves the die.

  • What kind of seating force are you seeing? Do they seat really hard?

    Are you orienting the bullet as straight up and down on the case as possible and guiding it up into the die as straight as possible?

    What is the actual runout measurement you're seeing, and where on the bullet are you measuring it?

    Is the seating stem making uniform contact on the bullet around the entire perimeter of the seating stem?

  • @tackyp said in Bullet Runout:
    I’m not sure what to do to fix this, short of trying to find a better seating stem

    It seems obvious, but have you measured the runout at that point of unused bullets? I agree, it's a very long shot. Is the rest of the cartridge straight or is there a chance your die is sitting crooked and the ogive is just the place you were measuring? The die body may be slightly eccentric.

    Rather than spend piles of money on new seaters or custom seaters, make your own using your existing die. Wax the inside of your die body and a concentric loaded dummy round with CLEAR/NEUTRAL Kiwi boot polish, degrease your seating stem, then put a small amount of a steel powder epoxy putty on the seating stem and run it down on the dummy loaded cartridge and let it set for 24 hours.

    It is important that the boot polish is clear/neutral, otherwise the pigment grains will allow the epoxy to bond. Same trick is used in epoxy bedding actions and recoil lugs. Other waxes may work as well but colored boot polish definitely does not.

    You may find it advantageous to raise the seating stem slightly to avoid having a zero thickness fit against the ogive which weakens the epoxy to steel junction. After you make this custom nose for your seater stem there will be a very close fit against the nose of the bullet so keep everything clean and dry when using it. [This really shouldn't be a problem since you are not using lubed bullets.] If you decide to change bullets or seating depth, the epoxy can be broken off the seater plug or ground flat for re-profiling.

    Best of luck.

  • Thank you all for the replies. I apologize for the delay in my response.

    Seating force is pretty nominal. Nothing to hard or soft. I have about 2.5 thou of interference fit with the case neck.

    I’ll admit I’m not guiding bullets into the die or really paying much attention to how vertical they are. I always thought the sleeve on the micrometer die did that for me.

    I’m seeing runouts averaging around 5thou measured on the ogive halfway between the tip and the bearing surface. I do occasionally get the odd high number; 15thou plus.

    Im not seeing any odd markings on the bullets from seating stems. I’ll check this in more detail next time I seat bullets.

    Thanks again all and sorry again for my delay

  • Take the ones with 15 thous runout (thats a lot) color them red with sharpie.
    Take the ones with 5 thous runout color them blue -- shoot them at a target at distance and determine if it really matters to you.

    This assumes rifle is in tune and capable of producing decent groups.

  • I only have one Forster die and it is for 458 Socom and I bought it under the presumption it was the type with the alignment sleeve. The standard seating die I got from lee was a pain to try and seat the bullets straight being it had no support of the bullet and if I didn't set them in really straight they would seat cocked even with the case mouth flared. I use Wilson chamber type seater dies for a few calibers but they don't offer one for the Socom so I bought the Forster but it isn't equipped with the sleeve. Not sure if they make one for this caliber. From what I know about Forster bench rest seat dies is the sleeve has to travel at least half way into the die body for it to align the bullet correctly. I assume your die is adjusted to do that. Boat tail bullets usually go in pretty straight with no help but it pays like Orkan stated to orient them straight as possible. There is a video I watched when I got my die made by Fortune Cookie or something like that on You Tube that shows the set up of Forster bench rest dies. The Forster 458 die does seat straighter than the Lee but I still have to be careful or I will tilt one. If all else fails ask for a new die, something may be not concentric in the die body or sleeve. Fifteen thousands is quite a bit especially if you have straight brass to start with. My two cents.

  • @bigfoot
    OOPS, I have a Redding die. No wonder it doesn't have the sleeve. Hornady claims to make the full support dies also but I opted with the Redding. My years are catching up with me.

  • @tan_90 You're not going to have to shoot rounds with 15 thousandths of runout to see if it matters. It does. A round that far out can land out of group by a long ways. 15 thousandths indicates a serious problem somewhere.

  • @orkan I agree 15 thous is an ass load of runout ....but sometimes our measurements aren't as good/consistent as we think.

    I've shot rounds with run-out vs no-run-out in my bench guns and they grouped together -- granted they were no where near 15 thousandths :). I don't bother to even check runout anymore.

    just my 2 cents.

  • @tan_90 Once you've got your loading techniques worked out and have certified your own equipment... the need for a runout gauge is often minimal. I agree with that. However, new gear can often be less than good, and when troubleshooting... runout is a viable factor.

    Comparing zero runout to rounds with say, as much as five thousandths of runout... yes it's possible you won't see them impact the target greatly differently. Though if you shoot a group and have 2-3 thousandths rounds mixed in with over 10 thousandths rounds... I've never seen that not show up if you're shooting 1/2moa or better or even close to it. I've seen that kind of runout hit as much as 1 moa from the center of an otherwise respectable group.

  • @orkan
    We are in agreement :)

    My main point is/was we must test our own stuff sometimes to see what does that 10 thous error do to my group.

    I also agree we all want perfect rounds!!

  • Shot some stuff this weekend.

    Runout all over the place 0-15thou with most about 6-8thou.

    Performance was better than I expected. Die is back to Forster now.

    In my mind I can’t see runout affecting performance that dramatically at 100 yards. Maybe if I was a bench shooter but not at that 1/2 inch range I’m at now. Obviously it’s an issue at greater range. I’m interested to see what happens if I sort out the runout and shoot those in groups. If it reveals itself to an issue at 100 yards this will possibly invalidate every OCW test I’ve ever done.