Chasing Ogives around

[YZ-80]

Ever find yourself seating bullets and getting CBTO variations of up to .007"? Today I was loading up some 143 ELD-X's for my 6.5 x 47 and usually, at the same setting on my Redding micrometer seating die, I might get .001-.002 variation and I usually don't sweat it. Anything over .002" gets my tightie-whites in a knot and I start correcting them. Sometimes, one will seat right on the money and the next one is .004" too deep. That's when I give it a couple of gentle taps with the kinetic hammer, knocking it out past the CBTO and then adjust the die and seat it again. Anyway, I have a feeling that this has something to do with lot to lot variation but what do you do when it happens? How much variation is acceptable to you?

 

[jdyoung]

What I do:
Anneal cases regularly...... make sure cases are clean inside...……. light polishing, ( more of a burnishing) of the inside of the case necks with synthetic "steel" wool wrapped around the proper size nylon bore brush chucked up and spinnin' in a drill, make one pass in and out of the case neck.

I also sort bullets according to the position of the ogive from the base. For that sorting, I originally used the Sinclair Hex Bullet Comparator and calipers. But now days the Lock n Load Bullet Comparator on calipers is easier/quicker.

 

[ShtrRdy]

I believe this could be caused by at least two possibilities.

1. The seating stem contacts the bullet at a different place than where the ogive is considered. If the dimensions of the bullet are not consistent you can end up with different CBTO measurement.

2. If the neck tension and friction are different from case to case the extent to which the bullet is seated can vary.

I like to count on the firing residue inside the neck as the friction layer. I simply run a polymer brush in and out of the case neck once to burnish it slightly.

 

[dok7mm]

The 143 eld-x was tolerances were the worst I've ever measured from base to ogive, weight variances and even diameter.

These were ordered when they first came out, so I can't say what newer lots are like.

If your necks are properly prepared and consistent, it's most likely BTO variance. The one other thing is to check your brass for donuts forming.

 

[elf]

If you are filling the case with a load, base of the bullet will compress it down, leading to erratic CBTO measurements.

Here is what I do: After charging each case, I seat bullets .005 - 010" high. Put each charged case in a seating tray divided by .001" CBTO each hole. Then I move my seater die down by the number of thousands each is over my target seating depth. Use the same amount of seating pressure each time.

 

[Tiny Tim]

Start with the bullet dimensions. Check the variation of the bullet BTO dimension. Have you checked/cleaned your seating die? A compressible piece of crud in it could give varying CBTO readings. Is everything in your seating die tight? Compressed loads may give trouble. All advice so far is good info.

 

[Hondo64d]

If your seating stem is bottoming out on the tip of the bullet, that will cause variations in seating depth. I don't know what die you're using but I do know that Redding offers both standard and VLD seating stems. The standard will bottom out on the nose of some VLD bullets.

John

 

[YZ-80]

Thanks All! Very constructive comments. This was virgin Lapua brass. I loaded 26 rounds with a 36 grain Varget charge. I do not believe that is compressed load, as I can shake them and hear the precious Varget inside.

By way of brass prep, it probably wasn't necessary but I just ran the necks through the expander button to make sure they were in round. I checked a few of them on the ball mic after that and they were pretty darned consistent at .013", so I decided not to turn them. Neck OD was the same after this at .288 and I ended up with .002 neck tension @ .290. I was targeting a CBTO of 2.133" and pretty much got them all within .001". The Seating die is a Redding Type S match die #36479.

I checked some of those ELD-x's too for BTO. I looked at 10 of them and they varied from .787 to .790.

 

[Tiny Tim]

Well that's. 003 of your .007 and only a sample of ten. That would basically cut your variance in half.

 

[LaHunter]

Ever find yourself seating bullets and getting CBTO variations of up to .007"? Today I was loading up some 143 ELD-X's for my 6.5 x 47 and usually, at the same setting on my Redding micrometer seating die, I might get .001-.002 variation and I usually don't sweat it. Anything over .002" gets my tightie-whites in a knot and I start correcting them. Sometimes, one will seat right on the money and the next one is .004" too deep. That's when I give it a couple of gentle taps with the kinetic hammer, knocking it out past the CBTO and then adjust the die and seat it again. Anyway, I have a feeling that this has something to do with lot to lot variation but what do you do when it happens? How much variation is acceptable to you?

I like to see a +/- .001 on my CBTO measurements. I load Nosler Accubonds and within the same lot, I get good consistency. When I change lots, I will set my seating die about .005" high, seat a few, then adjust my seating die to achieve my target measurement. Going to different lots, you may see a .005 difference. Also, your caliper could be part of the problem too. Some of the cheaper ones are not precise and may not hold their zero

 

[Mikecr]

I checked some of those ELD-x's too for BTO. I looked at 10 of them and they varied from .787 to .790.

Was this actually a contributor, or merely an observation?

 

[YZ-80]

Was this actually a contributor, or merely an observation?

Just an observation. Not sure if it contributed or not.

 

[Tiny Tim]

Is the tip hitting in your seating die?

 

[YZ-80]

Is the tip hitting in your seating die?

I don't know but I see where it would be relavent with the plastic meplat and variances with those too. Probably would not happen with a VLD seating die, I guess.