greaase groove ?

[XWrench3]

so i was looking at some of my cast boolits the other day. i was wondering why the grease grooves have square edges, instead of a tapered goove like the crimping groove does. it would seem to me (i know, i am just a rookie) that if the greas was shoved outward when fired by a angled groove, it would force the grease out against the barrel, and maybe lube better?

[mpmarty]

Ah sweet mystery of how lube works in a barrel.
IMHO centrifugal force takes care of getting the grease from the groove onto the barrel surface.

[462]

XWrench3,

I think Elmer Keith was the instigator for square grease grooves, because they hold more lube. Problem with them, though, is that they don't allow a boolit to easily release from the mould. Modern square grooves have an ever so slight radius to correct that problem.

Regardless of the design -- once a boolit is in the barrel -- rpm, centrifugal force, and inertia will make sure that the lube does its job.

[runfiverun]

a bullet making contact with the bbl can't throw nothin nowhere. spinning or not.
the square grooves are for lineal pressure [you know gas pushing on the base of the boolit]
for some odd reason they seem to be more accurate then rounded grooves the lube also has a tendency to stick in the grooves better than a radiused one while handling etc...

[462]

runfiverun,

The grooves, just that, they don't contact the barrel, allowing the lube to do its job.

This article, by Glen Fryxell, explains it much better than I can.

[runfiverun]

i've read glen's work, thank's..
and the lube i use is still in the grooves when it reaches the target not spun all over the inside of the bbl. lube is forced from the grooves from lineal pressure from the rear as the boolit deforms [obduration is the term]
waiting for 44 man......he'll tell us he want's it to fly off everywhere when it exits the bbl.
we do about everything different.

[HeavyMetal]

MY understanding of Kieth's explanation:

A square grease groove would compress from gas pressure on the boolit base and squeeze the lube out of the groove as the boolit traveled down the bore. Kieth maintained that boolits with rounded grease grooves did not do this and, as such, were more prone to leading if they were pushed to hard.

Let us remember that boolit lubes then are not what they are today!

This was/is the reason his 429421 and the 358429 originally had the square grease groove. Somewhere I saw Pictures, allegedly taken, or assisted by, Kieth himself showing both a square and round lube groove boolit after firing and recovery.

The square grease groove boolit was shorter by the width of the groove the rounded lube groove was in pre fired length / condition. In all honesty I don't remember if this boolit had lube left on it or not.

When Lyman made the change in both his designs the story is Kieth called the big guy at Lyman and read him the riot act and insisted his name no longer be attached to the molds in the catalog's Lyman produced.

How much of that is true I don't know.

I do know I've used molds with both groove designs and have never been able to tell them apart, performance wise. As to casting grooves with a complete 90 degree angle at the corners of the lube groove can be very difficult to get out of the mold!

Newer designs that have a more "trapizoidal" angle provide the same "compress ability" without the hassle of releasing from the mold.

With the correct lube for the alloy and pressure being "run" I don't think the groove design is as big a deal today as it was in the 40's and 50's.

As to the difference between a lube groove and a crimp groove?

Again this harkens to days past when Black Powder was the only gun powder choice. All BP loads are basically compressed and can push boolits out of a case over time. The crimp groove was designed into BP cartridge boolits to keep the powder compressed, the brass "folded in" and crimped the boolit in place keeping the BP compressed until the round was fired.

The crimp groove was a great aid in keeping boolits from "jumping" out of case's when smokeless powder arrived on the scene.

The shape of the crimp groove is different, and sloped, to allow the boolit the ability to "straighten" out a case without creating undue pressure while being fired!


At least that's my take on both grooves, hope this answrs the questions!

[Nora]

*Saids without authority to do so*

Let's hear it for Alox! Any style of groove will do!!

*Quickly ducks head and runs*

[357maximum]

*Saids without authority to do so*

Let's hear it for Alox! Any style of groove will do!!

*Quickly ducks head and runs*

I'll get the first one in ---- FUWACK ...what you say is true until you decide to go fast like a FLGC, and go fast accurately. Liquid earwax has it's place here in my stable also...but not on anything HOT and/or important. At that stage in the game some form of hydraulics mojo I will not pretend to understand comes into play and liquid earwax begins to fail in MY accuracy asperations.

[Bret4207]

We've had a couple good discussions on this. I think the best explanation for how lube works is this- magic! I say that because there will be 4 or 5 different explanations of how the lube gets to the barrel and they all sound like they work until the other guy comes in and explains why they don't.

My best answer on groove design? Tradition.

[Rockydog]

Hell, Round? Square? I'd just buy whatever Waks has on sale. RD

[XWrench3]

well, after shooting around 150 rounds of cast boolits today, both mine, and commercial, almost all of the ones i recovered had grease left in the grooves. and the majority of them, had most of it left. if it is still in the grooves, it is not lubricating the bore, it is sitting there adding weight, and possibly aiding in gas sealing. i need to chuck a few boolits up, and angle the back edge of the grease grooves so the weight of the grease (and the acceleration of the boolit will force it to the bore when fired. if there is no difference, fine, my theory will be proven totally wrong. however, in my simple little mind, the grease needs to go to the bore, and that is what i am going to try to make happen.

[runfiverun]

you get too much in there and you will have purge flyers.
if you use super soft lube you'll know it comes outta the grooves as it will be all over the gun inside and out,at least till it's fully in the bbl.

[armyrat1970]

I am no expert and have much less experience than many of you but, when you lube a boolit it just isn't getting into the lube grooves. It's over the whole boolit. Isn't that lube for the bore and the lube in the groove acting as a sealer?

[243winxb]

Square has more bearing surface on the barrel. Spin of the bullet spreads 50/50 lube. Alloy bullets should not obturate. Why do we see so many 9mm tumble lube bullets leading barrels? Its the design of the bullet letting gas get past the base, with improper lube, using less then 2%tin when air cooling.

[Bret4207]

If you figure out, definitively, how grease grooves work, what exactly lube does and what the "best" design of a groove is you will have answered question asked for over 100 years.