Bullet OAL and seating

[tisme]

I've would like to ask for your opinions thanks. I've been trying to seat bullets 5, 10, 15, and 20 thou off the lands to test using Berger 155.5. The problem is the bullets measure +/- 5 thou (measured from base to ogive). If i batch them and then seat the at the required depth then the bullet base will be closer or further from the powder increasing or decreasing the power?
How do others work up a load?
I've also measured other bullets with even bigger discrepancies.

Thanks

 

[3081FTR]

For the purpose of FTR shooting I don't worry about how much a bullet .005 longer might impact volume. Its impact isn't something I can measure reliably. Tight tolerance of jump to lands is something I can measure and see an impact on paper.
However shooting bullets of the same dimensions within any given string or group is never a bad thing.

 

[tisme]

Thanks for that, I'll batch some bullets and seat to length then test. I thought the case volume would matter more as I was told seating to lands was more about case volume than the bullet hitting the lands.

 

[3081FTR]

In my experience jump to lands is a critical measurement that has a large impact on group size. You can't alter seating depth without impacting volume. But I can chase the lands (affecting volume) with very small seating depth changes and have a load out of tune go back into tune. This volume change would be very minor relative to each cases variance.
None of this is intended to say volume doesn't matter as all inconsistencies ultimately matter.

 

[Zero333]

Never had a batch of Berger's that measured more than 0.002" from bullet base to bullet ogive.

Usually they're within 0.001", so seating depth mirrors the same measurement.

 

[3081FTR]

Never had a batch of Berger's that measured more than 0.002" from bullet base to bullet ogive.

Usually they're within 0.001", so seating depth mirrors the same measurement.

Seating depth as in jump to the lands doesn't mirror this variance (if thats what you mean) as its the variance in the nose "ogive" and where the seater stem touches it that causes (or is one of the causes) of seating depth variation.

 

[Zero333]

Seating depth as in jump to the lands doesn't mirror this variance (if thats what you mean) as its the variance in the nose "ogive" and where the seater stem touches it that causes (or is one of the causes) of seating depth variation.

Yes that's what I meant. If the bullets base to ogive varies by 1 thou, the cartridge base to bullet ogive should vary the same amount, if the seating die is working properly.

The OP said the bullets themselves vary 5 thou from bullet base to bullet ogive, and I never had a box of Berger bullets that varied that much.

 

[Shynloco]

For the purpose of FTR shooting I don't worry about how much a bullet .005 longer might impact volume.....

Perhaps I'm misreading what you are saying BUT, the OP said his bullets vary by .05 and NOT .005. And that much of a difference does alter his seating depth, volume as well as the jump to lands that's he's testing. So I would definitely group the bullets by ojive to base measurement and shoot them accordingly in the groups so his results are accurate and not a mishmash of uncontrolled test groups.

Alex

 

[ED3]

Perhaps I'm misreading what you are saying BUT, the OP said his bullets vary by .05 and NOT .005. And that much of a difference does alter his seating depth, volume as well as the jump to lands that's he's testing. So I would definitely group the bullets by ojive to base measurement and shoot them accordingly in the groups so his results are accurate and not a mishmash of uncontrolled test groups.

Alex

From the OP: "...The problem is the bullets measure +/- 5 thou..."

 

[Shynloco]

From the OP: "...The problem is the bullets measure +/- 5 thou..."

Ed,
That's what I said. The response I responded to made reference to .005 and not .05.

Alex

 

[ED3]

Ed,
That's what I said. The response I responded to made reference to .005 and not .05.

Alex

I guess I am is confused by your post. The only mention of .05 was your post, not the OP's.
I'm new to precision loading, and just trying to learn, and when I see numbers I don't understand, it sticks with me.

Regards.

Ed

 

[tisme]

I wrote 5 thou to not confuse things but it looks like I have. In engineering terms (uk) it's written .005 that's what I was taught 40 years ago. Sorry for any confusion.
From all the info I'll batch all my bullets and then seat and see how it goes.

 

[M-61]

I wrote 5 thou to not confuse things but it looks like I have. In engineering terms (uk) it's written .005 that's what I was taught 40 years ago. Sorry for any confusion.
From all the info I'll batch all my bullets and then seat and see how it goes.

It is written the same in the USA. FIVE THOUSANDTH's .005

 

[tisme]

It is written the same in the USA. FIVE THOUSANDTH's .005

Glad we all speak the queens English then, now if you could only say aluminium right.

 

[M-61]

Great Britain & the United States. Two countries separated by a common language.

 

[Comrade Terry]

now if you could only say aluminum right.

I fixed it for you.

 

[3081FTR]

Yes that's what I meant. If the bullets base to ogive varies by 1 thou, the cartridge base to bullet ogive should vary the same amount, if the seating die is working properly.

The OP said the bullets themselves vary 5 thou from bullet base to bullet ogive, and I never had a box of Berger bullets that varied that much.

ok - I can't correlate (and isn't my experience but YMMV) what you state as the variance is in sections that the seating stem doesn't push on. For instance if the variation is in the boat tail I can't see how that would affect seating depth in terms of final base of case to ogive measurement. There is potentially a correlation between a longer bearing surface and friction causing a variance in cartridge base to ogive but I have found that to be negated by small variances in neck tension and ogive variance, again YMMV.

I believe Bryan Litz latest book is going to talk directly to bullet dimensions and their impact on precision so it could be well worth the OPs time and money to get that book as a starting point.

 

[tisme]

Sounds like a good read ta