Why can't i reload exact cartridges?

[RockyMtnMT]

Looks like we need to define ogive.

 

[jsthntn247]

This is what the Bob Green tool is for. Their is variance between the ogive of the bullet and where the seater stem makes contact. Why they don't make stems to seat off the ogive boggles my mind. You can sort bullets with the Bob Green tool and if your neck tension is consistent, all your rounds will measure the same. You can accomplish this also by seating all bullets 10 thou longer, measure and group them and then seat to the final bto. This is why I do an OCW load dev for powder charge and seating depth and load in the middle of the sweet spot for both. If you do that, a half tenth of powder or .002 seating depth differences won't show up much on target. However if your shooting f class or bench rest you will want them all exactly the same.

 

[CanardNoir]

You may just be over-thinking the matter of a digital-caliper-measured dimension as a preconceived & absolute determinant of accuracy from a given rifle.

During the 1960s, when "long range" was closer to 300 yards, we simply used a permanent magic marker combined with periodic (finished cartridge) sampling - to determine whether the bullets/projectile was being seated to the proper depth, with respect to the barrel's rifling. After all - the critical distance IS that much smaller engagement distance (for a given, acceptable tolerance) based upon uniformity for a given rifle & expected load pressure.

We did experiment with micrometers, fixed sell length gages, and the like, but we seemed to always return to our mark-n-scratch-n-adjust method, for and before a deeper or shallower seating. But accuracy was never significantly better, than with that initial, manual method of seating a given bullet.

Moreover - 1) I'm not sure how you can accurately measure that small distance between the point of engagement with the rifling and a bullet's seated & chambered jacket; and 2) any adjustment you make to seating depth is simply a function of the combined threading of the a) die to the press, and b) the (finer threading) adjustment of the seating depth of the die. And the machined threading of each may simply add two (2) or more additional variables to the dimension of the finished round - depending upon the press and die manufacturer's machine tolerance to ASTM and/or SAE standards i.e. with respect to manual "adjustments".

Back with that RCBS stuff I used, I still checked every fourth or fifth round, after I set the bullet seating die with my master for that rifle and load. Then I loaded 10-20 additional rounds... My personal accuracy then, has never been bettered...

 

[TwoMore]

Looks like we need to define ogive.

I am 110% you know lol but heres a pic

 

[NEMTHunter]

Your incorrect sir. Take a black Sharpe and color the rifle bullet seat the bullet and you'll see the marks of the seater easily. You will see the seater does not seat at the ogive of the bullet. It seats more towards the tip of the bullet. Where the seating die contacts the bullet is a smaller diameter that what your bullet ogive is.

Not trying to start anything. But you just proved me right. A normal LR hunting bullet now days has either a Tangent, secant or a Hybrid Ogive. A hybrid is mixing the first to in this order Tangent then switching to secant for the remander of the length of the nose. The Ogive the the nose of the bullet. Most bullet Ogive's are not figured by a angle but by A caliber, That is the radials of a caliber. The tip of the bullet is the meplat. So if your seating stem is pushing on ANY part of the nose of the bullet between the bearing surface and the meplat, It seating by the Ogive. You cant seat a bullet by the bearing surface as we all know. So that leaves only the Ogive (which is the full length of the nose) or the meplat (the very tip of the bullet) and we know the seating stems do not seat by the meplat.

Hope this makes sense.

Looks like we need to define ogive.

If what I posted above is wrong. Please let me know.


ON EDIT: LOL looks like I was to late to the party. Or it took me to long to type.........

 

[TwoMore]

most comparitors dont hit the ojive where the lands first makes contact , but we measure and seat off the ojive because that part of the bullet is consistant.
edit another pic

 

[desertcrr1]

The source of variance in well-made bullets is not from the base to the ogive, but from the ogive to the tip. The length to the tip makes little difference to the ballistics, but the length from base to ogive does. If your seater stem does not touch the bullet on or about the ogive and is touching more toward the tip, you will necessarily introduce the bullet length variance into the cartridge length variance. If you send your bullet and your seater stem to RCBS and they will fit it to work with the bullet. At the same time, seat the same bullet in the same case ten times and note the variance in your equipment and technique. Measure each bullet to the tip and to the ogive and note variance. See where it coming from. Just measure one cartridge base to ogive 10 or 20 times and note your measurement error. You need to learn about sources of variance before it's possible to reduce it systematically. Shoot 10 loads for group that have less than .001 ES and 10 that have more than .004. Find out what's important to you before you chase it down the hole much further.

 

[Mach 1]

Not trying to start anything. But you just proved me right. A normal LR hunting bullet now days has either a Tangent, secant or a Hybrid Ogive. A hybrid is mixing the first to in this order Tangent then switching to secant for the remander of the length of the nose. The Ogive the the nose of the bullet. Most bullet Ogive's are not figured by a angle but by A caliber, That is the radials of a caliber. The tip of the bullet is the meplat. So if your seating stem is pushing on ANY part of the nose of the bullet between the bearing surface and the meplat, It seating by the Ogive. You cant seat a bullet by the bearing surface as we all know. So that leaves only the Ogive (which is the full length of the nose) or the meplat (the very tip of the bullet) and we know the seating stems do not seat by the meplat.

Hope this makes sense.


I don't care wether the bullet is a tangent or secant ogive bullet. I'm talking about the start of the ogive. Reguardless of bullet design the ogive starts at the same diameter per that caliber of bullet. I should have been more clear. The type of ogive is of no consequence in reguards to seating.

 

[rcoody]

Looks like we need to define ogive.

Many reloaders call the point where the curve of the ogive begins the ogive but in reality it is that entire curve from the point of curvature to the tip.

Variations in that curve is one of the largest reasons for variations in base to ogive measurements with most measuring tools. Even sorting my not solve this completely because the seater stem doesn't hit the curve of the ogive at the same point as the sorting tool. Different bullet manufacturers have more or less consistency in the curve of the ogive. My experience is berger and Sierra are more consistent then hornady or nosler.

Then we get to annealing or work hardened brass and consistent neck tension.

And then to in line seaters and arbor presses

I know it can be done. I can load 50 rounds without touching my seater and they will all be within a .001 base to ogive.

 

[Mach 1]

 

[Mach 1]

Many reloaders call the point where the curve of the ogive begins the ogive but in reality it is that entire curve from the point of curvature to the tip.

Variations in that curve is one of the largest reasons for variations in base to ogive measurements with most measuring tools. Even sorting my not solve this completely because the seater stem doesn't hit the curve of the ogive at the same point as the sorting tool. Different bullet manufacturers have more or less consistency in the curve of the ogive. My experience is berger and Sierra are more consistent then hornady or nosler.

Then we get to annealing or work hardened brass and consistent neck tension.

And then to in line seaters and arbor presses

I know it can be done. I can load 50 rounds without touching my seater and they will all be within a .001 base to ogive.

You hit the nail on the head.

 

[joseph gallagher]

All bullet dimensons are different, lot to lot and within lot. Even match grade bullets. For a variety of reasons. And variances in presses. All effect consistancy.
During a discussion with " doc beech" applied balistics, i questioned because of inconsistencies in bullet dimensions what was nore important a consistant amount of bullet in the case or a consistant measurement base to ogive.

Doc beech stated " having a consistant jump was more important that how much bullet was in the case.

Another thing the Hornady lnl tools are aluminum and wear.

This is my procedure, i use a redding competition seater, and a redding comparator. I have a dummy cartridge seated to reloading guide seating depth. I use this dummy round to zero the michrometer on the comparator. If i am seating .015 longer i just seat to indicator reading .015 greater than my set zero.

I back out the comp seating die .030 and seat then measure on comparator i do this 3x bringing the comp seating die down and remeasuring.

Following this i can get +- .001 base to ogive on like 40, 60 og 100 whatever i am loading.

Cant even depend on the micrometer thimble on the comp seating die bding 100% accurate

My 2 cents. What works for me. Extra work but it pays off

 

[okie man]

That's about the variance of one box of match bullets I mentioned earlier!

View attachment 122375

 

[Highdesertmike]

A lot of good information here. We are working with many variables when we handload and it's not an exact science. As others have said, the bullets are not all exactly the same, the seating stem may or may not fit the ogive properly, the cases are not the same as far as length, hardness and neck tension. All these variances add up in the end. Are your primers seated .002" Below the case head or are they a little proud? Primers are not all the same length. Are you using a quality caliper? Differences in technique can amount to variances as well. Are you lubing the inside of the case prior to bullet seating? Combine all these things and it's not difficult to vary a few thousanths.