Hi all.

A pretty straight forward question here.

When I go to make up rounds and seat bullet,go to measure the COL I might come up with 4 to 5 different lengths after bullet seating die is set to what lenght they should be.

What is the deal on this?


Every case is full sized and trimed the same so why would one bullet be say 4 to 10 thousands inch deeper or longer then the next one?

Is it the bullet tips are soft lead and they are messed up enough to cause this?

All measurements are done digitial caliper and checked with standard caliper.



Thanks all

I'll go first on this one.

When bullets are made, they often are produced on more than one press tool, often a bank of tools will produce completed bullets with each stroke of the press, accordingly the bullets coming off the bank of presses will reflect the dimensional tolerancing on the tooling that produced them.

As each press tool die will be made to certain tolerances, it is fasible and likely that bullets coming off 2 different presses will have different dimensions, but both will be in tolerance for the standard for that calibre.

As the bullet seating plug in your seating die will contact on a datum point on the ogive, then, if the ogive varies from one bulet to the next, then it is feasible for the overall length so to vary, that you mention that the length varies by only a matter of a few thousands of an inch, this bears out the variation in tolearnces of the press tools used to make the bullets.

if you are getting a wide variation, then try to work on an mean average so that the extrme spread on o.a.l is plus or minus .002".

hope this helps

alos it would be more of an accurate measurement to measure from the base to the ojive.
Stonypoint and several others make measuring devices that work for this.
Clean your seater especially if you use bullets with lead tips the seater plug collects shavings from the tips and that will create seating problems. check your case holder for crud. keep it clean.
try to use the same stroke and pressure each time you seat a bullet. clean inside neck will also help.
Buy a $100 micro adjust seater die

For a simple and cheap solution try using a Lee Dead Length bullet seater. As far as I can tell you'll need to use a micrometer seater to do a better and more consistent job. My experience says that RCBS seaters are the most variable, YMMV.

In addition, varrying neck tensions will require more or less seating pressure. Seating pressure, when great enough to swage the nose of the bullet into the seating stem, will adversly affect OAL. This means that instead of the bullet going down the neck, the bullet nose is being forced into the seating stem. If you are geting noticeable rings around the bullet nose where it is being contacted by the seating stem, then your neck tension is too high.

I use .0002" to .0005" max., meaning that the expander plug diameter is about .0005" smaller than the bullet diameter. This gives good neck tension for bolt action use. Semi-autos should use more than that, depending on the gun, to prevent bullet setback.

I recently loaded up some 7mm-08 rounds for a friend using 140gr Sierra Game Kings. I found that some of the COLs were different, then checked it out. The seating depths were the same, but because a few of the soft points were slightly flattened or misshapen, some of the rounds measured a couple of thousandths shorter than the others.

Thanks to all.

Seems to be the tips deforming I guess.

As hivelosity said will try this test on next run of rounds.

Really a crazy thing to have one dead on the next be out 3 or 4 thousands.

Don't want to reset the die on each round.

These are lee Pacemaker dies forgot to mention.

And on the subject of Lee dies had to send to them as the 7 MM deadlenght bullet seater was defective .

Case would not go into die all the way and as bullet was seated and ram backed down bullet would be removed from case.

Thia was a bear to figure out as it was the DELUXE SET

Again thanks to all.

Jon Tom is right. Hardcore benchresters know that bullets can vary slightly within a batch because they can still be within spec for weight, length and diameter even if they may have come from different machines. Best bet is to get a comparator and check each one. You'll most likely find you have three or four separate piles after you do 500 or so.