Runout issue, HELP!

[its only light]

Hey guys ran into a little problem that I can't seem to fix. I'm loading for my 338 lapu mag. I recently aquired a Sinclair concentricity gage from another member. Well I've been checking my ammo pretty religiously with it and been impressed for the most part. All the ammo I loaded for my 284 last week had a max bullet runout of .0015 with most being under that. I'm happy with that! BTW I used forester ultra dies for that.

Moving on to the 338 I havea set of standard rcbs dies. I took all the same steps with this stuff as I always do. My bulletin runout is between .004 and .010. Not happy with that! After fl sizing I had .001 on the neck. I've checked everything I can think of. There is no "donut". I took my seater apart and cleaned everything to no avail. My cases were trimmed and chamfered. Could this really be a problem with the die? I try to look what I'm doing instead of blaming my equipment right away but at some point it has to be a possibility. Any ideas?

 

[jelrod1]

My guess is excessive clearance in the seater and/or seater stem not matching the ogive correctly.

Even with a Wilson seater in .308 I have problems with SMK's. seating hornady or Bergers results in little to no added runout, but on the sierras I get .003 -.004. I have another different shaped stem coming from Wilson to try.

 

[its only light]

Hmmm I think your right. I took apart my die again after reading that and messed with it bullet and seater stem. The ogive on the stem sure doesn't match up at all with the ogive of the bullet. I'm using 300 SMK so sounds like you have been there.

So do I get a new die? I looked around and I don't think that rcbs offers any variations to address this issue. Thanks for clearing this up for me!

 

[treeman]

I believe rcbs will fix you up with another seating stem that better matches your bullet ogive. I have fixed the problem before by putting release agent on a bullet that is seated in a case and getting it as straight as you can and put a small ring of jb weld around the bullet where it will touch the stem rough up the inside of the stem and clean thouroughly put the die in the press and raise the case and bullet into the die and let it set up over night. it should seat the bullets straight after that. hope this helps

 

[kelbro]

I believe rcbs will fix you up with another seating stem that better matches your bullet ogive. I have fixed the problem before by putting release agent on a bullet that is seated in a case and getting it as straight as you can and put a small ring of jb weld around the bullet where it will touch the stem rough up the inside of the stem and clean thouroughly put the die in the press and raise the case and bullet into the die and let it set up over night. it should seat the bullets straight after that. hope this helps

I've done this with good results. With some VLD bullets, I also had to drill a hole through the center of the seater plug to accommodate the tip.

 

[its only light]

Good stuff guys. Think I will try that trick. Seems simple enough!

 

[bozo699]

I have fixed this problem before myself, I did it a little different, not saying above answers are wrong just giving you more food for thought, I also drilled for relief for tip of bullet then chucked up a bullet in a drill and with lapping compound started working the stem over with it, worked pretty well, now I use a optical comparitor at work and have our tool and die man grind them for a perfect match but the bullet with lapping compound worked okay. Also what is your neck tension and how hard physically is it to seat the bullet, you might want to brush the necks with a tight fitting brush then seat 1/2 way then rotate 180 and finish seating bullet, might help some, hope this helps.
Wayne.

 

[its only light]

I really like that idea. The jb is definitely a neat trick but I like the idea of actually lapping it to match. I will see if I can dig out my compound.

 

[jelrod1]

In my Wilson die, if the new stem doesn't do any better I'm going to make a new one that's bigger in diameter and open the hole up on the die. Then I'm going to "bed" a bullet into the stem with hopes that catching more surface area will solve the problem. My theory is that when it's not matching at least decently it magnifies the clearance issues by pushing the bullet to one side or the other allowing the neck to torque also.

The other thought is to machine out my Redding seater to accept neck bushings so I can play with clearances. I may try that with a Wilson blank too. Don't know yet. It ticks me off when all of my necks measure extremely good and my bullet run out is inconsistent. A machine shop is my business so I have the equipment, just have to find the time.

 

[its only light]

I agree. I'm a machinist by trade also. I work in a shop that makes gears and drivetrain parts for military vehicles and also alot of new stuff for the wind energy field. Alot of the stuff we do has a max .0005 runout call out so anything over .001 annoys me .01 makes me question myself as a person. Lol maybe not but I'm sure you can relate

 

[jelrod1]

Ha, yes I can relate. I have a program on my CMM that measures .308 cases inside and out in one setup. I've got some Lapua brass that I'm checking throughout their life and keeping tabs on them. It only satisfies my curiosity, but it's the nature of a machinist's mind I guess.

 

[bozo699]

Well since you two are Machinists then do As I do, I work for a company that has a state of the art machine shop and probably 45 or 50 machinists and tool and die makers, I simply buy several Wilson stems and take them in and have them and the bullet of choice ran on an optical comparator, then I have them opened up as far as I can take them without splitting out when seating a bullet, I did not do these things to help with runout as I have not had that problem in a long while, I believe runout is just in some cases and can't be fixed, those are for sighters and fowlers and that leaves the sizing die, If it is built properly and you are sizing the correct amount with it,not trying to size the neck more than .003 at once then usually I see very little runout on cases or loaded rounds, the more pressure it requires to seat the bullet the more of a chance your gonna have for induced runout. Now back to why I have the seating stems custom built by a tool and die man, I do it because the factory seating dies Wilson included touch the bullet just down from the tip instead of the ojive, so I try to make them the same shape of the bullet so they don't stick so bad and to try and open them up closer to the ojive, then I measure all my bullets using the seating stem usually or I build a deal for my comparator, I usually see .001 or less runout on the bullet at the ojive if it is .001 I straighten in on the concentricity gauge (tool) I use the Neco or the Sinclair concentricity gauges.
Wayne.

 

[steve4102]

All good advice, but don't forget to check the sizing die. In my experience most bullet runout is caused by the sizing die. A perfectly set-up seating die cannot fix what a sizing die has screwed up.

Try this, remove the expander plug from the sizing die, size some brass, now install the expander plug and open the necks up from the top down. No need to size all the way, just enough for the expander to open the neck back up.

 

[bozo699]

All good advice, but don't forget to check the sizing die. In my experience most bullet runout is caused by the sizing die. A perfectly set-up seating die cannot fix what a sizing die has screwed up.

Try this, remove the expander plug from the sizing die, size some brass, now install the expander plug and open the necks up from the top down. No need to size all the way, just enough for the expander to open the neck back up.

Steve,
That is what 90% of my post was about, proper use of the sizing die. 95% of the people on this forum do not use expander plugs, it's the first thing I remove when getting a new die, I am very careful not to drop my brass so my necks do not get dinged and I shorten ejector springs for the same reason, the bulk of the people on here use custom dies or at the very least Redding and or Forster Bushing dies, I have stacks and stacks of RCBS dies I haven't used for years just for that reason.
Wayne.