Copper bullet length/seating depth quandary

[.Skinner.]

Hi all,

I realise that there are endless threads about copper bullets, seating depth, ideal calibres for copper etc etc… I’ve enjoyed searching the forum for these and learning a lot, but have a question I haven’t found an answer for yet! So, apologies if it’s been done before but I did try!

Here goes….

So I understand that:
- copper bullets are generally significantly longer, given an equal weight, than lead bullets
- it seems that the above means that calibres such as (for instance) 6mm Creedmoor COULD be preferable to, say, .243 because the case shape means bullets can be seated further out. So to continue with this example, if you want to use a 100gr (and therefore very long) copper bullet in 6mm, the 6mm Creedmoor may be more suitable

However… I also understand that:

- copper bullets also generally like a significant ‘jump’ to the lands (upwards of 50 to 120 thou)

So, I will now do my best to word the question I’m getting at!

Is the potential ‘gain’ in seating further out, by choosing a cartridge with shorter/stubbier case length, actually quite minimal - being that you’re likely to need to be way off the lands anyway?!

By the way, I also understand that generally most people recommend going ‘light for calibre’ in copper… for this question though I’d like to focus on the issue of weights near the ‘top end’ of the calibre range - therefore very long copper bullets.

I hope this question makes sense, and may make for an interesting talking point! I’m no expert in ballistics or reloading, so apologies if this isn’t really a ‘thing’!

Thanks all

 

[yellow belly]

when I've done my load development, i have found seating to the first drive band/relief groove is most effective. However if you want more then a single shot rifle you will need to keep COL to just under mag size!

 

[jcampbellsmith]

I just buy factory non-lead ammunition from Edinburgh Rifles and Sporting Goods and go stalking.
Regards
JCS

 

[petlowe]

You are forgetting stability. Heavy for calibre projectiles will need a faster twist rate and a longer throat to work properly and avoid deep seating which means you are already out of factory choices unless someone has started making a dedicated factory rifle for non lead projectiles.

I would be looking at cases used in ELR competition shooting as they are already on heavy bullets looking for BC advantages hence faster teist and longer throat; 6mm Dasher, 6.5PRC, 6.5 284, 300 winmag etc.

 

[paul o']

When starting to use Fox 130gr I loaded as per Fox data ,that gave me a 1" group that to me was crap so I asked Edd who gave me his data and poi closed to .5 or less. Factory oal for the .270 think was 82mm and Edd's was 79.5 his data was bob on , they do like a jump well in my rifle anyway .270 A BOLT.

 

[308tikka]

6mm creedmoor is a slightly more efficient case than 243 but the reason people are moving off it is 1/scottish legislation 100gn and 2/ twist rate to stabilise.

Jump to the lands will be a function of how the chamber is reamed.

Just pick a cartridge chambering, load and have them jump 40thou. Or go through a ladder test at a pound per projectile to determine an accuracy node which will be irrelevant at stalking distances....