There are several ways to help limit your bullet run out. First thing you need to understand is what is causing your bullet run out from the beginning and in most cases its not when you seat your bullets.
Need to go back to the beginning. First off, virgin brass in general is not the best for getting very low, consistant bullet run outs. You need good brass and you need to fireform it in most cases.
After you fire a case, be careful when you eject the case by controling it as its pulled out of the chamber by your off hand. Take that case, run the fired case your concentricity guage. It should run very true, less then 1/2 thou run out or you have some issues with your chamber.
Once you prove that your chamber is good concentricity wise, now its time to start the process of loading your case.
What I do to check my FL die, if that is what your using, is to pull the expander stem out of the die. Screw the die into the press down to the point you want. Now DO NOT tighten the lock ring down on the die. Again, DO NOT lock the die in place. Will explain why in a bit.
Lube your case, run it up into the die to resize it and then clean it off and check for neck run out. There should really be no neck run out if your dies are in good shape and generally they are.
This tells you your dies are true. So why not lock the lock ring down. well, your press and your dies are mass produced items, as such there are variables in the machining that will result in a non concentric condition if the die is locked down into the press. This is because all those imperfections in the machining will then be transposed into your case and you will see more neck run outs.
Leaving the die loose will allow the die to self center if you will as you run the case up into the die and generally the neck run outs will be MUCH less using this method. If your worried about the case changing position in the press, take a black marker and make a reference mark on the die and press and you can visually watch to make sure the die does not rotate in the press as you size your cases.
So now you know your chamber is true and your die body is true. Next step and the one that generally causes the most problems with bullet run out in finished ammo is the expander stem.
If you now reinstall your expander stem into your set up die and run one of your sized cases through the die again, you will, about 80% of the time see that the neck run out inceases with the expender stem in the press, why?
Well, its because the case is unsupported when the expander button is passing though the case neck and it can be allowed to move in whatever direction it wants. This can range from just a bit of run out to as much as 7 to 8 thou in run out in the worst cases I have seen. So how do we fix this.
This will add a couple steps to your loading process using conventional dies but it will be worth it in the end as far as consistant ammo.
First thing you need to do is deprime your cases. You can either do this using a piece of steel spring wire and your shell holder on the work bench with a small mallet to tap out the primer or you can get a smaller diameter expander button so it will not touch your case neck when you pull the case out. You can also use one of the universal depriming dies as well.
Once you have all your cases deprimed however you choose to do it, There is a rather simple way to set up your die, WITH the expander button to produce much lower neck run outs in your sized case.
Take a fired case, clean and lube it. With your FL die in the location you want, Untightened, and the expander stem in the die at its conventional location, run your case up into the die. Leave the ram at its top position with the case in the die body. Now back out your expander stem as far as possible. If your using RCBS dies, this will work very well, if your using Redding or others with a different design, it will not work AS well.
Anyway, back off your expander until you feel it stop against the bottom if your case neck inside the case, then turn it back down a 1/2 turn so that there is some clearance between the case and neck with the case is in its top position in the die. Leave the expander loose!!!
Now, lower the case out of the die and you will nearly instantly feel the expander engage the neck of the case, before it has even been released by the neck of the die.
So what does this do for us. Well, we have proven that the die body is true already. AS such, we use that die body to control the case neck as we expand the case. As the expander passes through the case neck, the die is controlling the case neck for nearly all the length that it is being expanded. This will generally GREATLY reduce your neck run outs.
Neck run out is critical because whatever neck run out you have, this will be transposed into bullet run out in finished ammo. If your using a conventional seating die, generally you will see the neck run out often double when bullet run out is measured. This means if you are running 1 thou in neck run out, its not uncommon to see 2 thou in bullet run out in finished ammo.
My goal is to get all my sized cases ready to load with neck run outs of less then 1 thou. THey are not all to this level using conventional loading dies but with the system discribed above, most are.
With seating bullets, there is no real way to make a conventional seating die perform better.
In my opinion, its much better to get an in-line bullet seating die such as those from Forster or Redding. These dies have a sliding sleeve that controls the case as the bullet is being seated into the case neck. This greatly decreases bullet run out in finished ammo. I again leave these dies loose in the press.
With an in-line die, in most cases, the bullet run out will be basically the same as neck run out in the sized cases you started with. In some cases, it will actually be less then the neck run out, WHY?
Well, if the case necks are inconsistant in thickness, when you expand them with an expander button, the inside of the case mouth may be concentric but the variation in the neck thickness will be transposed to the OD of the case so your neck run outs will read higher then the ID neck run out. This is a good thing! That is why the bullet run out is often less.
If you want to correct this, take a very light neck turning cut to true up the case neck thickness or get better quality brass to start with.
These are the steps I use when using conventional FL die to size cases to get the best neck run out possible. For best bullet run outs, you really need a quality seating die. The Forster dies are not terribly expensive and well worth the cost. THe Redding Comp dies are much more spendy, very good but spendy.
If your using a Redding FL die, the steps discribed above will not work AS well but generally, Redding dies produce lower neck run out numbers anyway compared to other FL dies.
If your using Hornady dies, at least the newer ones, these methods will not work because then have an expander stem design that needs to be rigid to work.
Many will say using a neck bushing die will solve the problem. My answer to this is yes and no. If your using an S-type die, you can still get high neck run outs because the case is not controled by the die as the neck is sized. You do not have the expander stem issues but you can still get neck run out issues.
I have also had customers spend $200 on a full set of Redding Comp dies only to complain their bullet run outs are higher then they expected them to be. Why?
Well, with a neck bushing die, any imperfection in neck thickness is transposed from the OD of the case neck to the ID of the case neck. When you seat a bullet, the bullet will be guided by the ID of the case neck and as such, will result in higher bullet run outs.
If your using a neck bushing die, it is always recommended to either use the a brand of brass with consistant neck thicknesses or to take a very light truing pass with a neck turner to even up the case neck. That way, the OD and ID of the case neck are running the same run out value and your finished ammo will be much better quality.
Hope some of this can be of some help.
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