Why would 3 near-identical 6.5mm bullets produce 30/1000 of an inch difference in lands measurements?

[ddjchemist]

I reload 6.5 CM for my Tikka Tac A1 and primarily shoot Hornady ELD-Match bullets. For every new box of these Hornady bullets, I take 3 random bullets and measure lands distance using Hornady tools. Lands distance from the previous box was within 5/1000 of an inch for 3 measurements using 3 different bullets from the same box. However, I just opened another box (different batch) and now I am getting 30/1000 difference for randomly selected 3 bullets from the same box. Now I decided to measure just bullets' length, OGIVE and weight for these 3 bullets that are producing such difference in lands distance. I was expecting to find a difference between these 3 bullets, but both OGIVE and length are within 3/1000 and two of them are 146.8gr and one is 146.9gr. Does anyone have any idea what is going on? How can 3 bullets that are near identical when measured produce such difference in lands distance reading? I though that it could be me not doing accurate lands measurements. However, I measured lands distance 5 times with a same bullet and my readings were all within 3/1000. Keep in mind that the chamber and barrel are super clean.

Cheers,

Dan

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[Phred]

In my world, .030 (1/32") is a ton. Maybe worth a call to their tech line.

 

[P7M13]

Weigh, use a bullet comparator to check ogive.

 

[Steel Head]

I reload 6.5 CM for my Tikka Tac A1 and primarily shoot Hornady ELD-Match bullets. For every new box of these Hornady bullets, I take 3 random bullets and measure lands distance using Hornady tools. Lands distance from the previous box was within 5/1000 of an inch for 3 measurements using 3 different bullets from the same box. However, I just opened another box (different batch) and now I am getting 30/1000 difference for randomly selected 3 bullets from the same box. Now I decided to measure just bullets' length, OGIVE and weight for these 3 bullets that are producing such difference in lands distance. I was expecting to find a difference between these 3 bullets, but both OGIVE and length are within 3/1000 and two of them are 146.8gr and one is 146.9gr. Does anyone have any idea what is going on? How can 3 bullets that are near identical when measured produce such difference in lands distance reading? I though that it could be me not doing accurate lands measurements. However, I measured lands distance 5 times with a same bullet and my readings were all within 3/1000. Keep in mind that the chamber and barrel are super clean.

Cheers,

Dan

Welcome to the Hornandy bullet experience.

Changes are common, as is the down range disappearing act.

If you the type to be sorting bullets I really don't understand why you shooting their bullets.

 

[ddjchemist]

Weigh, use a bullet comparator to check ogive.

Yes, that is what I use, Hornady bullet comparator.

 

[ddjchemist]

Welcome to the Hornandy bullet experience.

Changes are common, as is the down range disappearing act.

If you the type to be sorting bullets I really don't understand why you shooting their bullets.

For now I will sort the bullets and measure lands distance for all of them. My rifle has almost 1,500 shots on the factory barrel, so I will soon have to replace the barrel (I shoot 250-300 rounds a months). After I replace the barrel, I will start using different bullets. It looks that Hornady has consistency issue between different batches. The previous 3 boxes of 147gr bullets were all between 146.8gr and 147.1gr. This new box (a different batch ordered from a different source) are between 146.5gr and 147.3gr.

 

[Member 34319]

I'd be curious what Hornady has for tolerances on bullet ogives. Sounds like they have some work to do.

 

[ddjchemist]

I'd be curious what Hornady has for tolerances on bullet ogives. Sounds like they have some work to do.

I measured bullet OGIVE and the difference is about 5/1000 in previous boxes and 10/1000 in the new box.

 

[Member 34319]

I measured bullet OGIVE and the difference is about 5/1000 in previous boxes and 10/1000 in the new box.

While you are getting differences, my question is whether Hornady measures these things and has acceptable tolerances on things like bearing surface, ogive, and secant radius. It would also be interesting to know what they measure when it comes to bullets if anything.

 

[Dozer99]

Welcome to the Hornady difference. There is a difference in every box!

That's the reason I won't use Hornady for accuracy loads, but they do make a good short range hunting bullet.

 

[DizzyJ]

That's a HUGE difference!

 

[ddjchemist]

Since my Tikka is approaching 1,500 rounds, so I will just use Hornady bullets since I will need to re-barrel the rifle soon. So far the rifle is very accurate, but it is 6.5CM, so I am expecting to have to change the barrel soon. After I get a new barrel, I will star using Barnes and Berger bullets. I have a couple of boxes of Barnes 140gr match burners and I measured them. They seem so much more consistent in all the measurements than Hornady. I will make some reloads with them and will compare accuracy that I get from them vs. Hornady 147gr.

 

[po18guy]

I reload 6.5 CM for my Tikka Tac A1 and primarily shoot Hornady ELD-Match bullets. For every new box of these Hornady bullets, I take 3 random bullets and measure lands distance using Hornady tools. Lands distance from the previous box was within 5/1000 of an inch for 3 measurements using 3 different bullets from the same box. However, I just opened another box (different batch) and now I am getting 30/1000 difference for randomly selected 3 bullets from the same box. Now I decided to measure just bullets' length, OGIVE and weight for these 3 bullets that are producing such difference in lands distance. I was expecting to find a difference between these 3 bullets, but both OGIVE and length are within 3/1000 and two of them are 146.8gr and one is 146.9gr. Does anyone have any idea what is going on? How can 3 bullets that are near identical when measured produce such difference in lands distance reading? I though that it could be me not doing accurate lands measurements. However, I measured lands distance 5 times with a same bullet and my readings were all within 3/1000. Keep in mind that the chamber and barrel are super clean.

Cheers,

Dan

Copy and paste this ^ into an email to Hornady's tech department.

 

[ddjchemist]

Copy and paste this ^ into an email to Hornady's tech department.

Will do it and see what they say.

 

[ddjchemist]

After thinking about the above mention issue I am having, is it possible that the lands measurement discrepancy that I am seeing is caused by some bullets just touching the lands and some getting jammed into the lands? When I use the Hornady gauge, I try to push each bullet with the same force. However, I am noticing some bullets come out more easily than others (when I push my wooden rod from the barrel front, some bullets come out with very slight touch and some need to be kicked slightly harder). Could this mean a difference is brass material quality from bullet to bullet? Could some bullets be a little bit softer than others?

 

[Steel Head]

After thinking about the above mention issue I am having, is it possible that the lands measurement discrepancy that I am seeing is caused by some bullets just touching the lands and some getting jammed into the lands? When I use the Hornady gauge, I try to push each bullet with the same force. However, I am noticing some bullets come out more easily than others (when I push my wooden rod from the barrel front, some bullets come out with very slight touch and some need to be kicked slightly harder). Could this mean a difference is brass material quality from bullet to bullet? Could some bullets be a little bit softer than others?

You have a barrel probably half way through it's life
That raggedy throat is hardly a precision measuring tool.
If your sorting/gauging bullets use bullet measurement tools, not a fire cracked throat.

 

[po18guy]

After thinking about the above mention issue I am having, is it possible that the lands measurement discrepancy that I am seeing is caused by some bullets just touching the lands and some getting jammed into the lands? When I use the Hornady gauge, I try to push each bullet with the same force. However, I am noticing some bullets come out more easily than others (when I push my wooden rod from the barrel front, some bullets come out with very slight touch and some need to be kicked slightly harder). Could this mean a difference is brass material quality from bullet to bullet? Could some bullets be a little bit softer than others?

Neck tension. To alter that, you could order an oversize/undersize expander, as the situation requires.