- Posts: 55
- Comments: 507
- Overall: 562
As goodsteel mentions the bullets, all cast bullets with lube, get sized down more than groove diameter from the lube between the bullet and the barrel. I also have recovered XCBs and others that were sized down .003 -.005″. I’ve tested 13 different lubes at HV and find that 3 lubes provide accuracy at HV the best; Javelina (no longer made), 2500+ and 2700+. I had hopes that PCing the bullets would eliminate the lube and provide better performance at HV. So far my own testing and reports of others is not providing better results at truly HV.
Before I discovered that “swaging down” I always wondered why I could achieve 2200 – 2300 fps with excellent hunting accuracy using a 323471 in a 10″ twist milsurp 8×57. I always attributed it to the Loverin style bullet. However that just never rang quite correct as the same Loverin style bullets in 30 cal wouldn’t perform the same in 10″ twist milsurp 30-06s. Now knowing the Mauser M98s in 8×57 had grooves .005 – .006″ deep verses the 30-06s .004″ deep grooves and that the bullets can swage down to less than the .004 deep grooves of the ’06 it’s logical that cast bullets don’t “strip” in the rifling as such. They just swage down at HV and the lands (rifling) just loses it’s grip on them. In the Mausers with their deeper grooves the lands still had a grip on the bullets.
Another problem is the tin in a ternary alloy. The tin is eutectic and conducts heat far faster than either lead or antimony. I lose GCs and accuracy above 2950 fps in 90+ degree weather out here. In colder 50 – 70 degree weather I push to almost 3100 fps before losing the GCs. Recovered GCs reveal alloy soldered to the inside of the GC. Mtgun has been very successful at 2900 – 3100 fps with his own designed bullets cast of a binary shot alloy which has probably 3% +/- antimony and no tin. He also HTs them to a very high BHN. You can see his results posted on his lube test thread on CBA. A very fine test BTW.
For hunting game (edible)with ternary alloyed cast bullets I’ve pushed the 311041 to 2500 – 2550 fps while maintaining excellent hunting accuracy out to 300 yards. At 2550 fps remaining velocity at 400 yards is 1450 fps so if accuracy holds it would still be effective on deer…..to 300 yards for sure. Since 99% of big game are shot on the short side of 300 yards (most are actually shot under 100 yards) a 14″ twist 26″ barreled 30 XCB or .308W would be just about the perfect 30 cal cast bullet hunting rifle.
One of these days either I or someone else will pop a deer or pig with a 30 XCB at 2600 – 3000 fps (muzzle) and see how it does. Cast of #2 alloy I, based on my experiments into wet pack newsprint, I do not expect the bullet to shatter as the pundits, with no actual experience, predict. I would expect some expansion and perhaps some sloughing off of the expansion petals. Still, it just remains to be tested on actual game.