Erratic Ignition with Heavy Bullets???

[randyf]

Just for kicks and giggles I loaded up some Cast Performance 395 gr. hard cast gas checked bullets.

I used 30 grains of Accurate 1680.

On my first shot I had a huge fireball, sounded funny, and my friend said you could almost watch the bullet going downrange.
My 2nd, and 3rd shot sounded better with little muzzle flash.
My 4th shot was like the first, and the 5th shot was like the 2nd and 3rd.

What would cause such a difference in the muzzle flash, and velocity.

I don't have a chroney, but could tell by the sound there was a difference in the shots.
I have been reloading for 30 years and measured the powder with a scale on each load.

I also loaded up some 350 gr Hornady jacket soft points at the same time using the same load and they all shot fine.

[commander faschisto]

I'm not one of the reloading experts here, by any means, but it sounds like you've got too much empty space in the case with only 30 grains in there (?)...that's usually what gets weird things going like you described. If I remember correctly, the recommendation is to have the case filled at least 90% to get consistent ignition.

The "loose fill" problem is actually quite dangerous, because ignition can become detonation...with unpredictable unpleasant results.

Hoot has a description on the site here of how to fill the empty space in the case using a separator cut from a piece of tissue paper (like, one layer of toilet paper), topped by your favorite flavor of grits to get the case filled under the boolit. You might use the search function to get the whole description of what to do.

[Hoot]

I have zero experience with boolits. Using 30gr of AA1680 you need a bullet that seats at least .55 inches down into the case to maintain the accepted safe minimum occupied space of 80%. The big issue however IMHO is despite 1680 burning ideally with bullets in this caliber weighing 395gr, it needs good neck tension as well and my limited understanding is that a lead boolit will not come close to a copper jacketed bullet for achieving neck tension. Now some of that is made up for by the weight, see Newton's 1st law. The lead boolit will also slide down the barrel with less resistance. Those factors to me would seem to imply that you need a faster burning powder than 1680. Heck I got hangfires from 1680 shooting 300gr jacketed bullets out of my 450 with a wicked double stab crimp laid on. Lastly, use Remington 7 1/2 primers. You need to bring the heat under low pressure to get 1680 cooking. Consider a little faster powder as well.

I can't model that load in QuickLoad because there are no 45 cal 395gr cast boolits in their reference database, so I can't recommend what charge to use with 1680, or any other powder.

When you crack the code, let us know.

Hoot

[pitted bore]

randyf-
Have you worked through the older threads on this site about cast bullets in the 450B? Posted on a sticky near the top of the reloading forum there's a list of cast bullet threads that I compiled: CAST BULLETS discussions

Please post your observations of successes or dramatic failures. Thanks.
--Bob