Load data question

[grubbylabs]

Hi all

Not only am I new to casting but also reloading as well so I come to you with a question.


I started out with a Lee .452 230 grain T/C mold after a while became unhappy with it and ordered a mold from Tom at Accurate Molds. I ordered a .452 230 grain RNFP The only difference besides the profile is that the lee bullet measures .63 from top to bottom while the Accurate bullet measures .6 from top to bottom, so can I use the same load data?
I loaded two of the new ones up with the same COL as for the T/C and they chambered just fine. So with a shorter bullet is it OK or do I need to find new data?

Any recommendations would be great.

I haven't shot them yet as I am not sure and don't need to blow up a gun or hand.

Here is a link to the bullets from Tom's catalog. I ordered the 45-230D (http://accuratemolds.com/img/bullets/detail/bullet_detail.php?bullet=45-230D-D.png) and the Lee mold is the same profile and weight as the 45-230E (http://accuratemolds.com/img/bullets/detail/bullet_detail.php?bullet=45-230E-D.png)

[AZ-Stew]

I suspect your flat point bullet will generate a lower chamber pressure when using the same overall cartridge length (OAL) as your previous RN design. The reason is that the FP is actually seated with the boolit base .030 farther out than it was with the RN. This leaves more (not much, but more) space in the cartridge of the loaded round. More space = less pressure. The same powder charge, using the same OAL should be safe.

I doubt you'll find any difference shooting the loads or in grouping. As long as the load you're using reliably functions the action and feed reliably, it's a "good" load. You may want to experiment with different powders and charge weights to find an accurate load, but as long as it functions well, you'll be OK with it.

Regards,

Stew

[grubbylabs]

I guess I should add that the T/C shot best with a max load of 5.7 grains of Unique. I used the load data from the new Lyman casting book.

So I might need to increase my charge a little to get the same pressure?

[geargnasher]

My universal advice is that if you change ANYTHING with your load, back off at least 5% and work back up with the new/different component. It's difficult to predict without in internal ballistics program exactly what will happen if you change one thing slightly, so it's best to drop back and work up again, even if just five reduced-charge rounds are tested.

Gear

[MtGun44]

The key points to consider are the amount of boolit in contact with the bore. More contact means
more friction and more pressure, less contact - less pressure; as a general rule. The most
important variable is combustion chamber volume. If you wind up with the base of the boolit
deeper in the case, pressure increases, and in small cases like 9mm and .380, it can go up
fast. With the .45 ACP, not quite so critical, but it still increases pressures and must be
taken into account.

All said and done - back down at least 5%, 10% is smarter and work back up.

Bill