Bullet seating depth varies: Whats wrong?

[milprileb]

I have a constant problem: my bullets in rifle loads are not seating at consistent depths.

Makes no matter if I use Lee, Hornady or RCBS dies: I get bullets seating at Plus and Minus.

Makes no matter if its BTHP national match Hornady bullets or pulled M2 ball, all my seater dies will seat bullets with varibles.

Last night, I was loading 7.5 French. Seating depth would vary from the setting of 2.900 that I set the die to seat at. My results were :2.903 to 2.892 with most of them running 2.895.

Is this normal or is there something I ought to fix or stop doing or what?

I get this type of fluctuation regardless if I use my Co Ax, my RCBS Rock Chucker or my old Herters Super O press.

I even stopped using any Lee O rings thinking they compressed or were part of the problem. I use all steel Hornady rings on my dies. My seating techniques is slow and steady as I try to be consistent as I can be.

Am I chasing fly dust here or is there a basic problem that I need to fix ?

[cajun shooter]

First of all your seating depth has a lot to do with the pressures that are reached when the round is fired, accuracy of that round, and even throat erosion of the chamber.
The best way that I have used over the years is to size the neck area of your case that has been fired in that rifle. Next take a bullet and hand start it into the case. After putting it into the chamber take the bolt and slowly close the bolt until it may be closed. Your bullet is now at it's furthest point in your chamber. You may take and either smoke the bullet or mark it with something that will show marks as it engages the rifling. If it shows marks of rifling then back off just a small amount and use that as your seating depth.
What type of dies are you using? Are you neck or full length sizing? What caliber and type of gun is this occurring in? Later David

[1Shirt]

Think that neck thickness may be a part of your problem, as well as your technique of seating the blt with consistant pressures. Don't know what brand(s) of brass you are using, but I would bet that there is a variance on neck dia either/or inside or outside dia. I personally would now worry with the variance that you list. Neck sizing may or may not help as well. Advise us of your progress.
1Shirt!:coffeecom

[milprileb]

I neck size my 303 Brit brass and get same variance as I do with I full lenght size same brass for example. This seating depth variances holds true on my FL sized 3006, 7.5 Swiss and 7.5 French loads as well.

As stated my dies are: Lee, Hornady, RCBS. My presses are Co Ax, RCBS RC and Herters O.

Maybe I need to neck turn the brass and eliminate a possible variable.

[milprileb]

David aka Cajun shooter:

I have done that with all my rifles: the bullet seating depth ideal for each is well known and seating die is set to that setting. So using last nights example with 7.5 French loading, the bullet depth set was 2.900 and my seating of bullets would range 2.892 up to 2.905 at times.
Average about 2.895. I am trying to seat each bullet with the care and consistent pressure humanly possible.

It costs as much to load an accurate round as a inaccurate round: that is why I am fixated on this floating seating depth issue

[Hip's Ax]

If you are measuring over all length (base to tip of the bullet) that is your problem. You need to measure from the base to the ogive with something like the Stoney Point OAL tool that goes on your caliper. The tips on MatchKings can vary 0.020" in the same box. You will find your ogive to base measurement far, far more consistent.

[milprileb]

So with 168 BTHP National Match, my readings if measured from tip vs from the ogive can differ. THus: my ogive's may all be seating to same depth and I don't have a problem.

A seating depth measured from tip of bullet to base of case COAL then is a flawed measurement
in realistic terms to achieve? My cases may have differing rim thickness so that enters into the equation ?

Just trying to hard wire this all down in my mind.

[bobthenailer]

A+ on the Stoney Point col guage I dont reload with out it , also after measuring col off the bullets ogvie your COL should be alot closer .
Another word of caution ! when you get a new box of bullets with everything being the same ! recheck the ogive COL with the new box of bullets . this doesent change to much if any with the same lot #, but different lot numbers will cange signfinatly in ogive col .

[obssd1958]

Hip's Ax beat me to it. I suspect that this is the reason you are getting varying readings. Your seating die has a cone shaped "pocket" on the stem (for spire point rifle bullets), and it pushes at the same diameter on each bullet. Where that diameter is in relation to the tip of the bullet varies, therefor, so does your overall length measurement.
Try this link for a visual:
http://www.sinclairintl.com/.aspx/pid=38769/Product/Sinclair-Bullet-Sorting-Stand
and click on the video link to the right, once you're on that page.

Don

[milprileb]

Then I don't have a problem ? My ogives are seated to same depth and the
mis readings I am getting is merely the variances of the distance from Ogive to
End of bullets nose.

Set the die to seat depth of bullet using that ogive accessory to calipers and all will be just fine ?

[Hip's Ax]

A seating depth measured from tip of bullet to base of case COAL then is a flawed measurement in realistic terms to achieve?

Correct. Especially in the case of HPBT match bullets the tips can range from rather smooth to very jagged. Grab your box of HPBT's and your caliper and measure from the base of the bullet to the tip on several, you will be astounded.

[Hip's Ax]

The only time I check OAL like you are is for rapid fire ammo that must function in a magazine. For single load slow fire ammo I only do the ogive to base.

Sometimes you will go through a tray of 100 rapid loads and find one that is a LOT longer than the others. I just take a file and knock the jagged part off of that one.

[Hip's Ax]

Then I don't have a problem ? My ogives are seated to same depth and the
mis readings I am getting is merely the variances of the distance from Ogive to
End of bullets nose.

Set the die to seat depth of bullet using that ogive accessory to calipers and all will be just fine ?

Correct.

[Hip's Ax]

An afterthought, if you are magazine feeding these rounds you must still observe the max OAL published in the loading manual. Make your lot of ammo then meaure them all and find the longest and set your seating die by that.

Usually anyone using a Stoney Point Comparitor (I previously called this the OAL gage, I am wrong) is also using a Stoney Point OAL tool with the matching drilled and tapped cartridge case. These are used to find out where the lands are so you can pull your bullet back from there to set "jump".

[bobthenailer]

I also ment to say Stoney point comparaitor in conjuction with the col guage

[Hip's Ax]

Another error on my part, these are now made by Hornady and used to be made by Stoney Point. :violin:

[Gillie Dog]

Then I don't have a problem ? My ogives are seated to same depth and the
mis readings I am getting is merely the variances of the distance from Ogive to
End of bullets nose.

Set the die to seat depth of bullet using that ogive accessory to calipers and all will be just fine ?

Maybe, possibly, could be, etc.

Yes it will help a lot to measure base to ogive not tip, that will give you accurate dimension to start of rifling in the front of the leade. This is considered the best way to measure seating depth, base to ogive, not base to tip because of afore mentioned variations in length of bullet from ogive to tip. This will tell you if it is the die or not. (Probably not)

If you are getting more than 0.001 or so inconsistency from base to ogive then, no your problem is not solved. I personally like no more than 0.002 inconsistency but to each his own. The Hornady comparator kit has been good enough for me and opened my eyes to what was causing my inconsistency. That and a concentricity gauge shows what is what in your process of loading.


Good luck

GD

[40Super]

You can also make a simple tool to check length,Take a round rod about .625diameter x 1inch long ,drill a .185 to .250 hole(depending on bullet dia) down the center. Square up other end or if you have access to a mill ,I milled an .125 groove(It fits over the caliper blade) about .425" deep.If it is made tight it can just be pushed on or drill & tap for a #8 or #10-32 set screw to hold it on the blade.Then you can measure how each round compares to the other.The number you get won't match up with the book oal,but it easy to figure out the difference.

[williamwaco]

I didn't see see this mentioned so I will toss it in.

You cannot reliably measure the overall length of the cartridge from the head to the tip of the bullet with a caliper. If you measure the same cartridge several times you will get differing lengths.

Remove the cartridge from the caliper, put it down and pick it up again then measure it. You will get small differences depending on exactly how the cartridge is aligned in the caliper.


.

[Jailer]

One other simple thing that I'm sure you didn't overlook but bears mentioning. Is your shell holder contacting the bottom of the seating die? It should come to a complete stop against the bottom of the seating die at the top of the ram stroke or you'll have a hard time getting consistent seating depths.

[milprileb]

Jailer, I understood if I did that, there is a crimp shoulder in the die that will crimp the case onto the bullet. I run die down till it touches and the screw it back 1/8 turn.

Is this wrong? If I did, then I appreciate any corrections immensely

[Jailer]

I know Lee rifle dies do not crimp but I can't speak for the others. The instructions that come with the Lee dies tell you to set up your seating die just as I posted.

This is the first paragraph from the Lee instructions for setting up the seating die:


Screw the die in until it touches the shell holder-then turn it in 1/4 turn more. This removes all play from the press and insures each bullet will be seated to a uniform depth. Bullet depth is controlled by the adjusting screw. This die will not crimp the bullet in place.

[milprileb]

Thank you Jailer.

I will do exactly that and see what happens.

[Jailer]

Thank you Jailer.

I will do exactly that and see what happens.

Make sure to report back as I'm sure I'm not the only one that is interested in the results.

I think you'll find that your OAL will only vary by a couple thousandths once you set your seating die up properly. At least that has been my results.

[milprileb]

I may be hosing this all up by improper die adjustment.

However.... on my Co Ax press, I think if I do as you stated, I will
bend up my sliding jaws.

I better call Forster and sort that out

[40Super]

That will work good since those dies dom't have a crimp feacture. Most seater dies do crimp so that method wouldn't work, as long as a person kows what die they have it'll work.

[daengmei]

I wondered about this when I first started and forgot to followup to find the cause. The measurement using calipers I did find varied, so I knew that was some of it but never considered the measurement should come from the ogive. After seeing the cost of those needed tools, I just make sure they fit the mag. When I have more experiece this will be a welcome tip, I'm not ready to fuss with bullet jump measurement yet. But should I? Is that the next step after being consistant with the press, powder, parts, etc?

[milprileb]

I talked to Hornady Tech Rep on this today and he told me to back that die off some
so the crimp does not engage case neck on ammo that I do not want a crimp on.
Some of my variances may have been seating & crimping at the same time ?

[.357MAN]

If you want a cheap ogive comparer you can FL size a case 5-10 times [ sizing makes the ID smaller and hardens the brass ] [ edit: ] trim to make mouth square then chamfer the case to your liking, presto instant comparer. It's not the easiest tool to use out there, but it's dirt cheep.