Benefit to a longer COL?

[TargetTerror]

I've read that a longer COL makes for more consistent ammo, and this seems like it would be true particularly in a smaller, high pressure round like 9mm Luger. Am I right in reasoning that with a longer COL, any minute differences in powder throws, bullet seating, crimping, or case dimensions (particularly with mixed brass 9mm) would be minimized? I reason that since the case volume would be bigger with a longer COL, any of these differences would be a smaller percentage of overall volume/pressure, and thus velocity differences between rounds would be lower?

Also, if I wanted to load 9mm to a longer COL, how should I adjust my powder charges to yield a similar velocity/power level? I assume I should increase the charge, but how much of increase should I do for various COL changes?

[Night Watch]

For pistol ammunition you're wasting your time! Don't even bother; and you might actually start causing yourself: magazine feeding, higher pressure, and forcing cone problems.

Rifles are a different story.

[Linear Thinker]

To make less work for yourself, you should seat near, but not at, the max COL for a pistol cartridge. This will maximize reliability, and reduce pressure. See the other thread on 9mm +P for the discussion of pressure and COL.

As Night Watch notes, the rifle issue is completely different, especially in bolt guns.
LT

[TargetTerror]

Ok nightwatch, magazine feeding and forcing cone issues I can see. But how would I get higher pressure but increasing COL?

[Night Watch]

By jamming the bullet into the leade.

[TexIndian]

He's right, except that before it gets that long you'll usually have some serious feeding problems. Also, by stretching out the bullet, the case neck doesn't have as good a grip on it, especially in a relatively thin-walled case like 9mm. So when it hits the feed ramp it tends to get sideways on you. It can even come out of the case under recoil from a prior round if not properly seated.

I also agree with nightwatch that this is something best left to rifle ammo where it can give some definite benefits in accuracy at longer ranges. I've never shot pistols competitively so I may be wrong here, but I've never heard of anyone stretching out their bullets except in bottleneck rifle loads where it can help eliminate inconsistent ignition. But even then, it can cause disastrous results if you don't know what you're doing. Until you digest a book with a comprehensive discussion of this technique, you'd be well advised to follow the length recommendations in your reloading manual.

[Night Watch]

If you'd like to build better pistol ammunition, build it to normal parameters using a powder that almost fills the case and gives you a nice consistent burn. If you want to go crazy, seal the primers and case mouths against oil and water contamination; then, use it as CCW carry ammo.

If I want better accuracy from a handgun I'll use hard cast, slightly-oversized lead bullets in a semi-wadcutter design. Other than this, better accuracy from pistol ammunition usually (but not always) starts with a better pistol!




PS: Watch your bullet seating and crimping, too. I tend to take these things for granted because I, somehow, managed to become expert at doing it. Properly seated and crimped bullets go a long way toward improving accuracy.