what is the best crown?

[Bart B]

the bullets are sierra varminter hp's,tested against much better accuracy oriented boat tail bullets.

For what it's worth, when I shot matches with Sierra's first ballistic tech and he was giving me a second tour of their plant in California, we talked about boattail vs. flat base bullet accuracy. He said that in the thousands of rounds of each he's fired in rifles, boattail bullets shot most accurate from best quality match barrels. The flat based ones shot most accurate from rifle company factory barrels and standard service rifle barrels that boattail ones. This was at their 100 yard test range in Santa Fe Springs. I've no experience shooting flat based bullets for accuracy.

The above aside, benchresters these days seem to get best accuracy with flat based bullets up through 200 yards in their excellent match grade barrels. But they don't use mass produced bullets for the most part at short range; they're usually custom made ones. Sierras and Bergers do well enough at the longer ranges.

 

[vegas steve]

i too have seen the same trend evolve in recent years, but am still baffled on how these economical flat based bullets group so well at longer distance.it made me think more about crown shape because these bullets and a few others like them didn't fair nearly as well out of my flat crowned barrels.

 

[Bart B]

i too have seen the same trend evolve in recent years, but am still baffled on how these economical flat based bullets group so well at longer distance.it made me think more about crown shape because these bullets and a few others like them didn't fair nearly as well out of my flat crowned barrels.

In my opinion, there's 3 reasons why any given bullet shoots better with the same load data in 1 out of 2 or more barrels all chambered with the same reamer fit to the same receiver that stocked the same way each time for each barrel. This eliminates all the variables except the barrel.

One's the groove diameter's equal to or larger than the bullet's diameter in the barrels that don't shoot too accurate. Groove diameters need to be a tiny bit smaller than bullet diameters; even as much as 1.5 thousandths smaller will shoot such bullets extremely accurate.

Another's the bore and groove measurements. Inaccurate barrels lapped and verified to perfect diameter dimensions most often have twists that aren't as consistant from leade to muzzle; a frequent issue with twist-gain barrels. Or there's other bore and groove dimensional issues

And finally, the chamber in the good barrel was better centered in the bore as its pilot matched the barrel's bore diameter and ended up with a better aligned chamber to the bore at its front end where it counts the most.

When variables other than the barrel's involved, accuracy comparison's a total waste of time, at least the way I figure all this stuff out.

 

[vegas steve]

my opologies bart,your opinions are very in depth and extremely knowlegeable. you are definetly a very well educated man of the trade.i behaved horribly twards you early on and you still offered information and patience with me. i promise to carry myself in a more professional manner from this point on and look forward to more insight from you.