Ogive and bullet jump measurement

[Sooter76]

This is a more generalized question but hopefully someone can assuage my overthinking...

I’m not a complete beginner when it comes to reloading as I’ve been doing it for a few years but at the same time being military with deployments mixed in I’m not as experienced as I should be. Anyway, I was reloading .303 British today using a Forester Ultra Micrometer searing die I recently acquired in conjunction with a Hornady OAL Gauge to seat the bullet based on the ogive. Using a modified case I measured the depth a few times and based my ogive seating depth of 2.344 off the average. Even with the Forester die my seating depth measurement varied anywhere from a thousandth to a hundredth of an inch (+/-). I realize this isn’t much, but when I trying to work up for accuracy I’d like to eliminate as many variables as possible.

So I guess my question comes down to this, should I actually be seeing any variations in ogive measurement with the Forester die? And if so, how much will the thousandth and hundredth variation effect accuracy/grouping?

 

[Steel head]

What bullets are you using?
Even expensive match bullets vary a bit.
Cheap bullets can vary a lot

 

[918v]

.010” is normal

 

[2aBaC̶a̶]

Are you talking overall case length measured base to tip? or using the Hornady comparator and measuring base to ogive?

Using this?

Lock-N-Load® Bullet Comparator - Hornady Manufacturing, Inc

Lock-N-Load® Bullet Comparator & Inserts Lock-N-Load® Bullet Comparator Measuring cartridge lengths across the bullet tips is not a reliable (or repeatable) method for meas...

www.hornady.com

 

[Sooter76]

What bullets are you using?
Even expensive match bullets vary a bit.
Cheap bullets can vary a lot

Sierra Match Kings

 

[Sooter76]

Are you talking overall case length measured base to tip? or using the Hornady comparator and measuring base to ogive?

Using this?

Lock-N-Load® Bullet Comparator - Hornady Manufacturing, Inc

Lock-N-Load® Bullet Comparator & Inserts Lock-N-Load® Bullet Comparator Measuring cartridge lengths across the bullet tips is not a reliable (or repeatable) method for meas...

www.hornady.com

Measuring at the ogive with a comparator insert.

 

[straightshooter1]

This is a more generalized question but hopefully someone can assuage my overthinking...

I’m not a complete beginner when it comes to reloading as I’ve been doing it for a few years but at the same time being military with deployments mixed in I’m not as experienced as I should be. Anyway, I was reloading .303 British today using a Forester Ultra Micrometer searing die I recently acquired in conjunction with a Hornady OAL Gauge to seat the bullet based on the ogive. Using a modified case I measured the depth a few times and based my ogive seating depth of 2.344 off the average. Even with the Forester die my seating depth measurement varied anywhere from a thousandth to a hundredth of an inch (+/-). I realize this isn’t much, but when I trying to work up for accuracy I’d like to eliminate as many variables as possible.

So I guess my question comes down to this, should I actually be seeing any variations in ogive measurement with the Forester die? And if so, how much will the thousandth and hundredth variation effect accuracy/grouping?

A variance of .001 to .010 is too much in my book. I use a Forester Ultra Micrometer seating die and get a variation of +/- .001. But, I didn't always get that until I made some changes in my processing. Variation in seating pressure, sometimes associated with neck tension (as you may already know) will cause variation in seating depth. And some boxes of bullets, often depending on the manufacturer, can have significant variation in the bullet's BTO measurement, which if significant will also effect seating depth. So, I test/measure about 10% of a box of bullets to see if there's any significant difference in the BTO's and if there is, I sort them in groups that are +/- .001. I also anneal after every firing to get consistent neck tension when resizing. Doing those things has got my seating consistency to that point, especially after having a box of SMK's that had a BTO variance of .034.

I don't know if any of that might work for you as it could be something else like an issue with the die's seating stem???

 

[2aBaC̶a̶]

Measuring at the ogive with a comparator insert.

I would expect a little better than +/- .01

I look for a few thou at most.

 

[Howland]

They are always going to be a little different due to different neck tension, slight variations in the profile of bullets in the lot, etc.

What I do is back the micrometer seating stem off about .010" from target, seat and measure. I'll usually be off around that much but rarely exactly. Then I just turn down the micrometer stem the exact amount I need. Often if you're trying to seat only 1-4 thousanths more, nothing will happen. You turn it down another .002, still nothing. Do it again and now you're .005 too short. I chalk that up to grip resistance.

I usually only get that anal when developing test loads except for a couple rifles. When working up seating depth test loads, I always seat the longest batches first. If one is too short, it just goes into the next group.

Doing this I can keep +/- .002 easily with most being +/- .001. With non precision/plinking ammo, I just set it to target CBTO and run with it.

 

[Dthomas3523]

.010” is normal

0.010 variance in BTO on seated rounds is normal?

I rarely see more than .001-.003

 

[918v]

0.010 variance in BTO on seated rounds is normal?

I rarely see more than .001-.003

I have had many 500 count boxes from Sierra containing two distinct bullets sometimes more than .010” apart BTO.

So I sorted them out but they shot the same using the same die setting.

So now I don’t sort anymore.

 

[straightshooter1]

I have had many 500 count boxes from Sierra containing two distinct bullets sometimes more than .010” apart BTO.

So I sorted them out but they shot the same using the same die setting.

So now I don’t sort anymore.

I'll bet if you had a difference of .034, you'd find that they don't shoot quite the same . . . particularly if shooting at long range. I once hand that kind of difference in a box of 500 SMK's and ran an experiment with them to see what different there might be and there was a difference in seating depth as well as average MV and at 100 yds there was a noticeable POI shift. So now, I run a sample test of each box and if there's a significant difference, I'll sort them. Most of the time though, my boxes of SMK's typically have +/- .002 and all the Berger's I've had have been better than that.

But I think you're right in your experience that .010 in most cases (particularly in shooting shorter distance like 100 - 200 yds) sorting them isn't gong to make any difference on paper.

 

[Deleted member 113831]

If it were a super 6mm something, then I'd worry. There is nothing chambered in 303 British that will show you the difference.

 

[hengehold]

If it were a super 6mm something, then I'd worry. There is nothing chambered in 303 British that will show you the difference.

agreed. You will not notice a difference in performance out of a rifle chambered in 303 Brit.

I use Redding competition seating dies and Sierra/Berger Bullets. Typical seating depth variance is about .001-.004” measuring off the ogive.