Depth of lube groove

[wv109323]

I was wondering what the minimum depth of a lube groove can be? I suppose the width would make a difference . Also what lube would you use in a shallow lube groove? Caliber is .38 special at target velocities and bullet weight of 160g.

[RU shooter]

For 38 at target speeds a tumble lube like LLA or bens liquid lube work just fine they work on any kind of lube grooves at less than magnum speeds

[JBinMN]

The multiple lube grooves on the Lee Tumble Lube style boolits are not very deep, but there are more than a few of them, so they can probably hold just as much lube as 1 or two lube grooves on the other type of boolit, depending on the depth & width of grooves made.

I reckon that when designing the boolit( & mold) one needs to factor in how much bearing surface is needed for the boolit to work well to make for a stable flight after leaving the barrel, & how much lube would be needed to lubricate the bearing surface as the boolit goes down the barrel. Since the barrels can be different lengths, I would reckon that lube groove tend to be designed to accommodate the longer/longest barrels & boolit travel in the barrel, so the lube grooves in the design are likely a bit of over kill for short barrels. Think is that it wold be better to have more lube than necessary, rather than not having enough & fouling the barrel.

Interesting to think on. I have not considered this before now, and I will enjoy seeing the posts here in this topic as they are posted from any who are "in the know" about this topic & how boolits are designed to work well.

[RU shooter]

Also to add even rifle bullets at higher speeds don't need all that much lube from my own experiences and reading the posts of others here . Some do very well with only the gap between the gas check and the end of the shank lubed . If your shooting black powder that's different. A good lube goes a long ways

[Rich/WIS]

Many of the bullets we cast are "vintage" designs that were intended for lubes that were not as good as modern lubes. In many designs it is overkill with lubes like 50/50 or Xlox 2500. IIRC when using the 50/50 formula Col. Harrison found lube was only needed in the bottom groove of the Lyman WC molds. In the old NRA reloading guide he had a good write up on lubes as well as other factors when using cast bullets, based on actual test firings.

[gwpercle]

There is no "minimum" depth that I'm aware of .
Elmer Keith liked one deep and wide groove , 358477 , 358429.
Ray Thompson , 358156 used two shallower , narrower lube grooves .
As far as I can tell with a good lube both work .
Reading in Elmer's books he at times was limited to beef and mutton tallow based lubes...might be why he needed as much lube as a boolit would hold .
Gary

[JonB_in_Glencoe]

Is there a "why" question buried in your "what" question?
If not, and you are designing a boolit mold, then I'd suggest comparing several other similar designs and find the average, and go with that.

[waksupi]

You need to fill the rifling grooves plus .001-2.

[stubshaft]

What he said unless your are going to PC.

[wv109323]

JonB,
Yes there is a "why" to the question. I bought a .38 mold that was a 158 g. swc. The mold had one large lube groove near the base of the bullet with two crimping grooves up front.
I could get no accuracy out of the bullet. I am talking 3 foot groups with keyholing at 50 yards. I had other molds that were fine.
I took the mold and removed as much of the lube groove as I thought I could ger away with. I set the mold up in a drill press and clamped the mold down. I hand turned the spindle to remove the groove. The lube groove is now about .004" to .005" deep. The bullet weighs 163 g. now. I have yet to shoot any.

[JBinMN]

JonB,
Yes there is a "why" to the question. I bought a .38 mold that was a 158 g. swc. The mold had one large lube groove near the base of the bullet with two crimping grooves up front.
I could get no accuracy out of the bullet. I am talking 3 foot groups with keyholing at 50 yards. I had other molds that were fine.
I took the mold and removed as much of the lube groove as I thought I could ger away with. I set the mold up in a drill press and clamped the mold down. I hand turned the spindle to remove the groove. The lube groove is now about .004" to .005" deep. The bullet weighs 163 g. now. I have yet to shoot any.

Please share your testing results.

[JonB_in_Glencoe]

I ain't no expert on BP cartridge loading...but if the big lube groove is noticeably bigger than is typical, I bet that boolit was designed for loading with a Black Powder charge.
With that said, I sure don't know why it would give such poor accuracy when loaded with smokeless powder?
I'm guessing, there is something else going on, that is giving your poor accuracy.
I look forward to the results of your test.

[Tim357]

JonB,
Yes there is a "why" to the question. I bought a .38 mold that was a 158 g. swc. The mold had one large lube groove near the base of the bullet with two crimping grooves up front.
I could get no accuracy out of the bullet. I am talking 3 foot groups with keyholing at 50 yards. I had other molds that were fine.
I took the mold and removed as much of the lube groove as I thought I could ger away with. I set the mold up in a drill press and clamped the mold down. I hand turned the spindle to remove the groove. The lube groove is now about .004" to .005" deep. The bullet weighs 163 g. now. I have yet to shoot any.

Would that be a Lyman 357446 perchance? That boolit needs to be driven hard to get decent accuracy, according to my buddy that uses it. Don't know if it's the wide base driving band, but that's his theory.

[Frank V]

I was wondering what the minimum depth of a lube groove can be? I suppose the width would make a difference . Also what lube would you use in a shallow lube groove? Caliber is .38 special at target velocities and bullet weight of 160g.

In the .38 special at target velocities I've used SPG with complete satisfaction. Just fill the lube grooves. I've used it to velocities of 900 with complete satisfaction.

[Green Frog]

In the .38 special at target velocities I've used SPG with complete satisfaction. Just fill the lube grooves. I've used it to velocities of 900 with complete satisfaction.

If you are thinking about what gets used only in 38s at target velocities, just about anything will probably work. Remember that one of the most commonly used bullet types is soft staged lead with very light knurling “lubed” with paraffin and mica or graphite. Not much volume of lube there,

Froggie

[Bloodman14]

Not to hijack, but I had a similar question about the volume of lube grooves, and whether I had enough lube. My question was answered, but I'm not sure I fully understood it!

[john.k]

On recovered bullets there is often a lot of the lube still in the grooves.......now if I assume some of the remaining lube was knocked out by the impact with the dirt,then it seems very little actually lubricated the bullet,and all the rest is wasted.......So how deep do the grooves need to be?.......and as for blackpowder,I suspect the most effective position for lube is a wad behind the bullet,where the fouling gets the max benefit of lube softening.

[country gent]

As lube grooves get shallower it may become harder to get them to hold lube and fill out correctly. The shallower the groove the mire pressure it may take to get lube to flow. For smokeless loads I believe most carry more lube than is needed for most uses. For black powder loads barrel length is more the determining factor, along with temp / humidity. A 30"-34" length barrel will require more lube than a 20" barrel. The grease cookie is used more since none is carried out with the bullet. Some is blown out but its still there wetting the fouling before its gone.

[DonH]

I think that with smokeless powder it likely takes much less lube than we might think. For some years I shot a 220 gr plainbase spritzer with 3 shallow lube grooves from my .32-40. I was able to shoot that bullet at 1400-1450 fps with only the bottom groove filled and no leading. Just now thinking about it that bullet was pan lubed which left a film of lube on most of the bearing surface so the bullet carried a bit more lube than it appeared to.

The OP mentioned large groups and keyholing which makes me think bullet fit rather than how much lube the bullet carried.

[lar45]

When I drew up the C358-180RF I went with .015" at the suggestion of some of the members here and it worked out very well. There has been more runs of it than I have kept up with. For lube I initially used Carnauba Red or Xlox 2500+ and both worked well in handguns and rifles.


I had a reject mold that was a 45-325SWC that the lube grooves got accidentally almost wiped out. It was a 2 cavity mold with different profiles in each. I cast both cavities to keep the mold hot and on a whim lubed and shot some out of my 454 Raging Bull and they shot great with no leading at all.