I do not know what it is but the Sierra .4295 220 gr. FPJ Silhouette shots the best of any bullet so far out of my 5 1/2" SBH. I have loaded it over Universal, Green Dot, and IMR 4227 in mag and special from 800 fps to 1100 fps and it shoots great in all. I plan to push it a bit more just to see if it holds up but there is no reason to believe it will not.
I can't say this about the 240 gr. XTP. It is .430.
I shoot mainly moderate velocity loads and this may have something to do with the XTPs not working all that well for me. That's why I plan to spice them up a bit as I get better at shooting a little heavier loads.
The 180 gr. XTP does real well in all the special rounds I have tried.
Now I am going to speculate a little here and say that it is possible that the Sierra is a little softer and therfore expands a little better in the barrel at the lower velocities thus stabalizing the bullet in the barrel better thus increasing accuracy. After saying this I have to say that I shot a rabbit the other day with one of these bullets and the entrance and exit holes were identical and no sighn of bullet expansion was seen. I did not recover the bullet so this is all speculation on my part.
In general, .001 inch over bore diameter will give the best accuracy in a cast bullet. The throat diameters also make a difference. You will have to measure both to get a correct fit for your gun.
I recently purchased a Ruger 44mag and a Smith and Wesson 44spl. Both have .429 bores and cylinder throats. Both work just fine with .430 bullets.
You will find that jacketed bullet accuracy will vary with the pistol. A little experimenting will find a good load.
The Sierra 180gr bullet is a big game design and probably doesn't eqpand on a rabbit. The bullet jacket is thick and the lead is hardened.
Stranger, I doubt it. There is another thread over in the "Handloading Practices and Procedures" topic where a guy is having trouble getting ammo with .430" cast bullets to chamber! The throats on his gun must be pretty tight.
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