Any idea why the Sierra 220 Gr bullets are keyholing in the 30-06 ? (Listed in the accurate loading pages)I snagged a batch of them at a recent gun show but haven't rolled any yet. I will be shooting them in Springfield 03's with original barrels. Any idea if twist rates will be incompatable???

Which 220? Sierra makes a couple of them.

And...you're gonna need a fast twist rate to stabilize that 220 (either one) at '06 velocities.

[ 03-07-2003, 08:36: Message edited by: ricciardelli ]

The Matchkings are not stabilizing in your standard twist barrel, I believe sierra puts that right on the box (for fast twist barrels only) or at least they do with the 22cal MK's.

With all due respect to ric, the original twist of the '03 Springfield was for the .30/'03 cartridge which used the same 220-grain bullet as the .30/40 Krag, a 220-grain round-nose. This was 1/10". When the 150-grain bullet was adopted, the twist was left the same (1/10"). Julian Hatcher related an instance in which Springfield Armory was getting exceptional accuracy out of a certain lot of '03 Springfields when testing them. They found that a gear on the rifling machine had slipped, and it had rifled a bunch of barrels to 1/11" twist. This twist was much more accurate with the 150-grain bullet. So, what do you think the Army did? Right!! They reset the rifling machine to original specs, so it would give a twist of 1/10", as it was supposed to do, even if this twist was less accurate! Your twist is plenty fast for round-nose 220-grain bullets. Unless possibly you are using an abnormally long bullet, it should work. You can use the Greenhill formula to calculate if your 1/10" twist should work. This formula is: Required twist IN CALIBERS = 150 divided by length of the bullet IN CALIBERS. For example, a 1.35", 220-grain .30 caliber bullet is 4.5 calibers long. 150/4.5 = 33.333 calibers, or 9.99". This is just slightly faster than 1/10" twist. 1/10 will work for this bullet. I would try the issue barrel before buying a faster one!

My (older edition) of the Sierra manual shows them using the 220-grain HPBT Matchking with a 1/10" twist .30/06, and no mention of any problems with that bullet due to the rate of twist.

[ 03-08-2003, 21:28: Message edited by: eldeguello ]