Why are Lube Grooves the way they are?

[303Guy]

It seems to me that lube grooves are typically too wide and too deep leaving too little width to engage the rifling. Loverin designs seem better but still have narrow drive bands. So I'm wondering why the lube grooves shouldn't be shallower and narrower, perhaps with more of them?

[country gent]

Keep in mind the grooves have to carry enough lube for the trip down the barrel weather its a 16" or 34" length, the old maker dosnt know when they make the mold where it will be used, or what lube will be used. The grooves also have to allow enough area for the lube to grip and hold in. Lubes have to flow into these grooves also shallow wide grooves would up the pressure needed. Tumble lube bullets are coated completely nose bearing surfaces metplat base and grooves. The ration of groove to band also control friction in the barrel.

[JSnover]

What's important is the length of the bearing surface (with exceptions), I.e., the distance from the base to the front edge of the forward band. The amount of surface contact doesn't have to be all that much for most applications.

[Larry Gibson]

Most cast bullet designs are from "back in the day" when there weren't the modern lubes we have today. Unfortunately the designers of newer bullets look to the older designs for lube groove size, number and shape. The lube grooves for todays lubes (started with the classic NRA 50/50 lube) do not need to be ad wide or as deep as the grooves of old.....but they usually are. Lee started a more modern trend with the TL designs and narrower and shallower designs on his bullets. It was also thought back in the day that the lube grooves were supposed to collapse a bit and somewhat force the lube onto the barrel somewhat like a grease gun. With hard cast bullets that do not collapse and modern lubes it is found the huge, deep lube grooves are not needed.

Larry Gibson

[bhn22]

Yup, in a word... tradition. LBT uses really narrow lube grooves in some bullets, but by and large, people want to see the really large lube grooves that aren't really necessary anymore. Modern lube formulations are much more effective than beeswax and mutton tallow.

[longbow]

No arguments with what has been said but an observation or two. Elmer Keith seemed to like large square lube grooves in his "Keith" style SWC's and they work well in both handgun and rifle (in my experience anyway) yet there are also designs like Lyman's 311299 which has very little groove diameter bearing surface, relatively narrow driving bands, shallow and rounded lube grooves, yet that design is also a winner.

Also, many people say that using Loverin designs which have plenty of room for lube that they only lube one or two grooves which puts them in the same category of lube capacity that the 311299 has ~ small.

I have had no problems with my 316299 NOE boolits leading even with my home made lube so obviously they carry enough in a rifle barrel.

On the other side of the coin, I have had ACWW Keith 429421's collapse in the lube groove when using heavy loads (recovered boolits tell a tail). And when I say collapsed, I mean to the lands so that would certainly act as a grease gun and squirt about all the lube out. It can't be too good for accuracy though. I was doing penetration tests with those loads so accuracy was not checked. The fact that a book load of Blue Dot caused that boolit to collapse indicates that the alloy was not hard enough.

I have also had 316299's skid a bit showing wider grooves than lands in the boolit (again, recovered boolits tell a tale). Oven heat treating fixed that. A slower powder might also help if the acceleration is a little gentler.

My view is that many boolits have lube grooves that are too deep, leaving too small a diameter to resist the pressure of heavy loads. I think that if a boolit fits well, it does not take a lot of lube to make it through a barrel.

I guess I am with 303guy. I like a lot of bearing surface and relatively shallow lube grooves.

I am sure there are a lot of opinions here though. Different strokes.

Longbow

[btroj]

Only issue I have with some Lee moulds is the shallow grooves, they seem to be prone to letting to of the lube in storage.

Tradition is hard to stop in shooting sports.

[Mal Paso]

The market is controlled by the lube groove dealers.

A couple of the major loob groove dealers run this forum.

Just a word to the wise about being TOO critical of loob grooves.

[btroj]

So Waksupi is the Cheaper Than dirt of the loob groove world?

Can I be banned for saying that?

[longbow]

Oops! I meant to say "I love lube grooves! The more the Merrier!"

Are we good now?

[bhn22]

Nice recovery guys.

[GabbyM]

I've a couple rifle bullets with pencil thin lube groves. They do just fine.
Even the Saeco #243 which runs all the way down a 26” bore. My other 6mm boolit is a Lyman Loverin with lube galore. All that extra lube doesn’t seam to help or hurt it. Both bullets fail at the same velocity and powder charge. One is 87 grains the other 84 grains.

Maybe if you had a goofy washboard of a barrel surface. But really the gas either blows by to ruin the whole works or it doesn’t. I’ve never experienced much in between. Nor heard where a bigger gob of grease would fix that. Have heard the term “run out of lube”. When people get leading down towards the end of a barrel. However I’ve never been convinced that’s an accurate description of the problem being experienced.

Black powder boolits seam to benefit from great gobs of lard and wax. So perhaps the large grease groves are more of a holdover.

[prs]

My boolit's groove is bigger than your boolit's groove! Nah na na na nah na na na nah na....

prs

[Old School Big Bore]

My quarrel with most of the Lee designs is not so much the grooves but the bands. The front band is so dinky and hard to fill, you have to crank the heat and run the molds on the edge of warping to get a good fill, and then the boolits are so crystalized they look liable to crumble or shatter. Same with the base bands, they're so meager it's hard to get a sharp fill. Most of their designs would have benefitted from moving some lead from the center bands up and down to the base and front bands, using a taller groove. They got it right with their 45-200-SWC which is pretty much a copy of the H&G #68; if they had done that with their WCs and SWCs their boolits would have been easier to cast and perhaps more popular. ARRGH, this has turned into a Lee rant, I guess...

[waco]

So Waksupi is the Cheaper Than dirt of the loob groove world?

Can I be banned for saying that?

You can, and should be.......

[freebullet]

I can only add that with pan lube a large deep loob groov makes things easier in my experience.

[waksupi]

So Waksupi is the Cheaper Than dirt of the loob groove world?

Can I be banned for saying that?

Why, I oughta.........

[303Guy]

Thank you all. That's an interesting and informative insight.

I can only add that with pan lube a large deep loob groove makes things easier in my experience.

OK, that was a surprise. I was thinking shallow and narrow grooves would be better for pan lubing.

I'm also surprised that wider bands make little or no difference. I was expecting deep and wide grooves to collapse easier, especially if close to the boolit base. I have observed lube being left in the grooves which may or may not get thrown out in flight.

What about the shape of the lube groove? Does it make any difference if they are square or angled? Square would increase the bearing area and would hold lube in better (as in preventing it from flinging out) but then angled grooves would fling it out more reliably.

[GabbyM]

Another thing that has not yet been mentioned.
Cutting tools are used to cut molds. There's a fact I wont have to don my flame suit for.
So you're grinding this cutter to make money with. Old mills used a thing called a cherry. Anyway you want it to last more than a few minutes. So do you grind a tooth on it that is .062" wide or .100" wide? Pretty obvious even to people who've not burned up a few hundred thousand dollars worth of tooling as I have.

Then you have the issue of being able to fill the mold when casting. Some of us know little groves need an expensive high tin alloy to fill nice.

In the end it needs to look like something John Wayne would shoot in a movie.
Then to be contrary . There are those Lyman molds with the little nose groves you couldn't fit a fishing line into.
Like my 225646. I know how they do that but I'm not telling. Can't understand why they don't charge extra for those however.

[eljefeoz]

Thanks for this.
I have asked this question in other places, and since this has begun anew, may I ask, how/what determines gas groove design?
Agreed, the mould manufacturer has to cater to a large variety of usage patterns ( and keeping economics as a priority) and lube.if one were designing a CB, for say a .309" or .286" smokeless load, to run with, say, NRA 50-50 or Ben's Red specifically, would the design parameters change so drastically? Yep, you guessed it, I'm a lube noob, and find it very therapeutic, making up lubes.
Cheers and TIA