Reloading--Manual vs Convention (copper bullets)

[JimmyHoffa]

When reloading copper bullets in the past, when there wasn't any load data available I would use a little thumb rule.  That was to take the bullet weight and add 15%, then use the closest lead bullet that did have that powder.  So for a 150 gr copper, would look for a 170-ish grain lead which usually ended up being the 165-168 grains.  This was to account for the extra volume of copper (compressed load).  Anyone ever hear of this?
So I got a new manual because I couldn't find anything with a new powder to try (IMR 4451 Enduron).  I noticed the manual doesn't make any mention of differences for the length of the bullets.  It has all the bullets grouped by weight:  A 150 gr GMX (copper) is listed with say a 150 gr interlock SP (copper jacketed lead core).  Even listed as having the same COL, even though side by side the GMX is longer.  The maximum charge listed would be the same, yet the copper sits further into the case.  Just kind of made me wonder.  Is the former advice for using data for the 15% heavier lead bullets just not needed (never was)?  Just burned up more powder during load development by starting even lower than what is now a 'starting point'?

[Platensek-po]

Interesting. Would like to hear about this and bump this up

[Jolten]

I believe the COAL is max Sammi spec always. And the powder being the same due to needing just as much force to move an equal amount of weight down the barrel?

[JimmyHoffa]

If I look at the exact same bullet (ex the 180 gr interlock SP) and the same powder RL-17, both listed to be loaded to the cannelure--same depth/same weight bullet, but one goes in the .30-06 and the other goes into a .308, the 06 starts at 47.0 grs and the .308 is at 47.1 grs before the highlighted dangerous territory load is (max recommended).  Then the consideration is from case capacity/pressure.  But the manual says you can load a copper max load the same charge as a lead core for the given weight/powder, but you have a different case capacity.

The manual I'm looking at is the Hornady 10th edition.

[yorketransport]

It has just as much to do with bearing surface as it does bullet make up and weight. Newer monometal bullets have a much shorter bearing surface than the older designs (like the original Barnes bullet), so sometimes the same data can be used for the same weights in lead core and solid copper. When you get into the copper bullets with very short bearing surfaces like the Cutting Edge, Flatline, Badlands, and Hamemers, you'll actually get to a point where your charge weights will be higher with the monometals than they are with a similar weight lead core bullet. A lot of the solid coppers are using different alloys than they used to, so that changes things as well.

[hogslayer]

I have been playing with Hammer Hunter bullets in 338 NMI.  I am becoming a fan. This was my three shot zero for hunting today. 24” barrel H1000 2980 FPS.   Copper doesn’t swell like lead does.  Same charge for 250 Berger (shortest bearing surface of all time) was 3050.

[JimmyHoffa]

Okay, that sounds like a good explanation.  The bullet description does say that the new gilding for the metal is friction reduction as well as mentions bearing surface changes.  The old monos that I am used to are Barnes TSX and TTSX, where I used to do the quick volume compensation.  My assumption was based off initial pressure.