Bullet seating problem

R

RedSkyFarm

New member
I'm loading 25-06 shells and am using RCBS dies. Two sets of bullet seating dies are making a ring on the bullet as it seats. First die set was used. The second seating die is brand new. Ring is from the seater itself as it pushes the bullet into the case. Appears to be very clean inside the seater. Any suggestions on why this is happening or how I can get rid of it?
 
Welcome to TFL

It's not totally uncommon to see the ring on the bullet . It's often just a smudge and will have no effect . If you are getting a gouge or dent that you can feel . Then there is something wrong there . How ever if you can't feel an indentation on the bullet you should be GTG .
 
Not really much of a problem, just annoying and caused by the slightly sharp opening of the bullet seating stem where contact is made with the bullet during seating and may not occur with a different bullet. Remove the stem and the sharpness could probably be smoothed out with fine emery paper or the use of a polishing compound. Just a cosmetic issue.
 
Are you neck sizing or FL? Did you chamfer the case mouth?

It sounds like you have the die screwed in too much and it is starting to crimp the case as you are pushing the bullet down. I like to crimp as a separate step. You can do this by backing the die out two turns, seating the bullets and then removing the seater plug and screwing the die back down to do the crimps. I do this as a batch operation so once 20-50 rounds are seated I then go back and crimp those 20-50 rounds.
 
Good point above. If you are starting to crimp before the bullet is fully seated, that would put a more pronounced ring on the bullet. So as first step, back off some on the crimp, if that is what you may be doing and see what difference that makes. If no crimp is being applied, then consider smoothing out the bullet stem opening if still considered worthwhile.
 
I don't believe that's what he's describing. Even my Redding Competition Seater die leaves a thin ring on the bullet where it contacts the ogive, and I don't have any crimping going on at all. It's just that the edge of the ram end of the seating stem is sharp enough to leave that mark.


RedSkyFarm,

Welcome to the forum.

I've shot many a cloverleaf with bullets with that mark. The mark is far more shallow than rifling marks are, and those don't affect the ballistics appreciably because they are shallower than the air boundary layer around the bullet in flight. So if you aren't getting a dent your caliper can measure at more than about 0.005" deep, and if your mark is symmetrical around the bullet, then its only impact is cosmetic.

I've also seen these marks on commercially loaded match ammunition.

If the mark bothers you, remove the nut at the top of the seating stem and take the stem out of the die. Gently (so as not to ding the threads) chuck it in a variable speed drill or a drill press set to low speed, or chuck the nut in the drill and let the threads turn in until they bottom out in the chuck. Then turn the seater while running touching the edge of the ram lightly with a felt bob loaded with polishing compound turning in a Dremel tool. If you don't have a Dremel tool, you can wrap some 600 grit wet-dry paper on a pencil or dowel and gently radius the edge of that ram a little while it turns, following up with Flitz or other polish. The main thing is to keep it turning constantly so you don't get an asymmetrical result. You want this thing bearing on the bullet evenly.
 
Thanks for the responses. I'm not crimping at all. The ring does appear to be cosmetic at this point. I've since put some dykum in the seater and there is a slight change in the angle of the inside of the seater approximately 3/64" from the bottom. I will try Uncle Nick's suggestion and attempt to polish it out (on the used seater first!). Thanks again.
 
BTW, an accuracy tip: Get a Lyman M die for your chambering. With jacketed bullets you don't need a flare, as you do with cast bullets, so just set it up to put a step in your case mouths that lets you set the bullet in it to start straight into the case. It's and extra step but it can shrink groups as much as an MOA, depending on bullet shape. It works especially well with the RCBS dies, because the long, thin, threaded RCBS seater stem flexes enough to allow self-centering. You will want to set it up so the crimp shoulder comes just close enough to crimping that it removes the step created by the M die.
 
I have had this same problem with Forster dies.

They cut the concave shape of the seater stem and then de burr it.
When I look at it under a microscope, there is still a small burr.
So I de bur the de bur.
Even then, there is still a slight problem looking at the seated bullet under the microscope.

Then I read on a forum that some guy is dedicating a seating stem to a particular bullet by glass bedding the bullet. He puts release agent on a bullet and seats it over a period of 6 hours while the epoxy sets up.

I have not actually done the glass bedding myself. But I appreciate I cannot debur my way to a perfect fit. The shape of the seating stem is a compromise, and it is going to touch at a ring unless is is perfect. By deburring the deburring I can get to where I cannot see the ring on the bullets with the naked eye, so out of sight, out of mind.
 
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