Pondering those grooves...

[LeadThrower]

All things being equal, what is the effect of taking a boolit from 1 lube groove to 2, 3, etc.?

And to avoid claims that I'm a lubist (... I said lubist, not nudist!...) I'll rephrase for the bandists (... not bandits!...) in the crowd:

All things being equal, what's the effect of increasing the number of driving bands, keeping total % driving length a constant?

Are there applications where extreme is inherently better than the other?

These sorts of questions keep me up at night... soooo much to learn!
:coffee:

[Bullshop]

I never seen a Loverin I didnt like.
BIC/BS

[45 2.1]

Indeed, loverins are nice, but they do seem to have a velocity limit due to their short band length along the boolit. Multiple bands and grooves are easy to size down without distorting or "unbalancing" the boolit while long length drive bands distort and are harder to size if changed much from as cast condition. this distortion really displaces metal along the length of the boolit into the lube groove if not filled. It also changes the length of the boolit, and you really don't know how much damage you have done to it if that happens. The bearing length should occupy some % of the boolit. How it is spread out depends on potential usage and size range if you have enough room to do so.

[pdawg_shooter]

+1 on the Lovern design. Easy to get to shoot good and ideal for reducing down for paper patching. Now if I could find a mould for a 30cal 210gr Lovern I would be a happy man !

[Ben]

Yep....Never met a Loverin that I didn't like ! !

http://img.photobucket.com/albums/v494/haysb/88.jpg

[Bullshop]

Perty poor shootin if ya couldnt hit it in 5 shots, wink wink.
BIC/BS

[Blammer]

another picture of a missed dime.... when is someone gonna hit it! :)

[Blammer]

I think taking a bullet and increasing the number of lube grooves would have two affects.

Increasing the lube capacity, sometimes for the better.

reducing the drive band width, as stated earlier when resizing bullets it's easier when the drive bands are really wide especially when sizing considerably.

[MakeMineA10mm]

Making the individual drive bands narrower, as long as you keep the same percentage of bearing surface, would also reduce pressure somewhat. With the loads CBs are normally used, working pressures are low enough that I don't know why one would worry about this, but it is there, nonetheless...

45 2.1 - Do you think that a wider base band, combined with Loverin-style (or similar) multiple, narrow lube grooves farther up the bullet would work well for combining accuracy with pressure/velocity-handling ability?

[Bass Ackward]

1. All things being equal, what's the effect of increasing the number of driving bands, keeping total % driving length a constant?

2. Are there applications where extreme is inherently better than the other?

3. These sorts of questions keep me up at night... soooo much to learn!
:coffee:

1. If you have a fixation about lube outside of the grooves, you have more spot that can be hidden by the neck. If you have really wide or tall rifling as they did years ago with cut rifled barrels, then thinner bands engrave easier. They also had poorer lubes when loverins were designed, so they needed the extra capacity. If you have a short (light) for caliber bullet, then more grooves means a longer bullet for the same weight if you have to reach the lands. Longer bullets generally have a higher ballistic coefficient too, but not always. Bob already told you about sizing. Smaller bands will size easier if you have to shoot much over bore diameter or displace lead like a 2 groove.

2. If you have low rifling height or want to drive a bullet beyond normal levels, then I would want wider bands. IF I was shooting close to bore size, I would want wider bands. This may require a better grade of lube too of which we have many. Larger bands mold easier / better with less rejects and a wider temperature operating range. (less corners) Thinner or wider bands can alter balance points if that is necessary.

3. While you are up, think about what you want this bullet to do under what conditions. It'll come to ya. IF it don't and you guess wrong, it will still go bang and you can do something else next time.

[DonH]

I shoot a 220 gr .323 PB spitzer designed about three or four years by Barry Darr. Barry was foing EXTENSIVE testing using the Oehler 43(?) Ballistic Lab system. This long-for-caliber bullet has WIDE bands with two pathetically-small looking lube grooves. It looks like it just flat does not carry enough lube but does not lead. I have kept it below 1500 fps but this style bullet has been driven yp to 1700 fps or so. I believe the velocity limit to be the plain base rather than lube carrying capacity.

[45 2.1]

45 2.1 - Do you think that a wider base band, combined with Loverin-style (or similar) multiple, narrow lube grooves farther up the bullet would work well for combining accuracy with pressure/velocity-handling ability?

Up to a point. There are quite a few old Lyman designs like this, especially for the leverguns.

[oso]

. . . Are there applications where extreme is inherently better than the other? . . .
:coffee:

Handguns don't equal rifles and don't require Loverins, IMHO. What is your application?

[HORNET]

IIRC, Phil Sharpe recommended that the lube grooves be half as wide as the bearing bands. Of course, we have much better lubes now so that many of the old Loverin designs now carry more lube than necessary at conventional speeds. Paul Matthews did some experimenting with shallow grooves quite some time back that showed some potential, as well as some recent tests on this forum with micro-groove designs. Kinda depends on what your goal is.
I still think it's hard to go very wrong with a Loverin design in the middle of the weight class for its caliber.

[LeadThrower]

Oso,
The only application I have in mind is hunting. Mostly I'm just looking for knowledge and insight. Some of the points raised have already come to mind, many of them have not. All are appreciated greatly!

I thought that if we had all the data and time in the world, some data-mining would show a relationship (empirical equation) which related alloy BHN, pressure, total driving length fraction (of total length), and individual driving band lengths (as fraction of caliber or total length). And from Bass: "If you have really wide or tall rifling as they did years ago with cut rifled barrels, then thinner bands engrave easier." So rifling depth and width would go in the equation, too. An impossible quagmire, if ever there was one.

[Bass Ackward]

So rifling depth and width would go in the equation, too. An impossible quagmire, if ever there was one.


LT,

Look at some of the bullet designs from yesteryear. Some of these Lyman designs are over 100 years old. Handgun and rifle. Why do you think that you find so much variance? Don't you think that they could have perfected a cast bullet design by now? :grin:

If something worked for all situations, all bullets would look pretty much the same? Especially with the width of the bands? That's a guy swears by one design while another swears at it.

[LeadThrower]

Don't you think that they could have perfected a cast bullet design by now? :grin:

If something worked for all situations, all bullets would look pretty much the same? Especially with the width of the bands? That's a guy swears by one design while another swears at it.

BA,
Indeed. I get your point... or meplat, whichever you prefer. :)