Front Band Length question

[Haywire Haywood]

Is there a practical limit to how long the front driving band can be? I was looking at the chamber impression of my 357 Maxi and the boolit that Veral sent me using it as a guide. Judging from how it sized, it looks like the front band is about .130, enough to reach past the leade into the throat proper if I load it out just shy of exposing the first lube groove. There's no hope of engraving the rifling, the chamber is about .062 too long in the neck for that.

Just trying to get an understanding of boolit design do's and don'ts.

Ian

edit: punctuation correction

[felix]

Ian, it is a function of diameter and length of that first band, or whatever you want to call that amount of sized-lead sticking out past the end of the cartridge case. Ideally, that shape should match exactly the angle of the leade of the chamber. But, that is impossible when using today's store bought lever guns because the length sticking out of the case in totum will be too long to cycle from the magazine. You have to have a compromised boolit to work as intended by the legal department, or shoot single shot, or rechamber the barrel, requiring a new barrel. ... felix

[Haywire Haywood]

Everything I load cast for are NEF Handi-Rifle break action single shots. :wink:

Ian

[Bass Ackward]

Everything I load cast for are NEF Handi-Rifle break action single shots. :wink:

Ian

Ian,

Well life can be pretty simple some times. But not usually with the circumstances you describe in your throat. And cast will amplify those poor dimensions not only from fit but with poor ignition with anything but the fastest powders.

If you have to jump, I would go wide for strength. I have designed bullets with .200 front bands that shot well with the right lubes. But reaching out and touching the throat is merely a matter of bullet weight. The trick is to find a compromise between those two factors. I would suggest a trunicated cone design where the nose length is kept short so that the front band reaches out as far as it can. Or better yet a semi wadcutter. And be conservative on meplat size. Unsupported nose weight is the enemy. Go wide on the lube grooves. This makes the longest bullet for the weight. And don't fill them if you don't need them.

The disadvantage here is that you will have lube grooves exposed, but you CAN reach the holly grail. My guess is about 210 grains.

[Char-Gar]

I designed a heavy 210 grain 30 cal bullets with a front band of .200. It was for the Krag rifle with the long throat. It has worked well in several 30 cal rifles in addition to the Krag.

I suppose there is a practical limit to everything, but a top band of .200 is not to long for a 30 cal bullet.