.....round bottom or square bottom grooves....

Todd Birch · Post by **Todd Birch** » Sat Mar 13, 2004 2:27 pm

What's the consensus on grease grooves in bullet design.......
round or square bottomed?

Does one have an advantage over the other insofar as function is concerned? Does one hold onto lube any better than the other?

Todd

flintski · Post by **flintski** » Sat Mar 13, 2004 7:56 pm

Todd:

Most all the custom molds today are square bottomed but I have heard tell that the round bottom lets the lube out easier than the flat bottom. I do think the flat bottom holds more lube than the round one. I have only one LBT mold that is round, but I haven't had any leading or more fouling than the square bottom molds. I myself just like the looks of the square grooves over the round. Accuracy wise I really can't see any difference. But then again I'm only a AA shooter.

IronSight · Post by **IronSight** » Sat Mar 13, 2004 7:57 pm

Todd,
All things being equal, i've always gone with square grease grooves but i must admit, never thought on this issue that much, just instinctively went with the square grooves.
The square grooves theoretically will hold more lube since there are no radiuses to reduce the groove volume.
Now some claim these radiuses will allow all the lube to be ejected in the barrel (easier) with no residual lube left in the bullet going down range. Now they may have a point if a hard lube is used..can't say i always use a soft lube with BP.

Another consideration is barrel length. None of my rifles has a barrel length shorter that 31". It might be a short barrel would benefit from a radiused grease groove, not needing the extra lube. Can't say for sure.

I've never found any residual lube left in the square grooves from my bullets recovered down range. Thats my story and i'm sticking to it.. unless someone proves me wrong of course!!

Todd Birch · Post by **Todd Birch** » Sat Mar 13, 2004 9:57 pm

Thanks for the feed back guys.

Maybe the answer is a matter of what's easier for a mould machinist to make, depending upon block material and cherry cutting tools.

I like the idea of the extra lube carried in the same width of a square bottomed groove. The counter to that would be to make a wider round bottom groove, or three instead of four grooves......and so it goes.

Boy, you can tell who the rifle cranks are by who's on-line of a Saturday night.
Whatever happened to younger women, faster cars and older whiskey?
Now it's "does she like guns", an ol' beater and the occasional beer if I don't spend all the money on powder and lead.

We're slowin' down guys - or have we discovered the real meaning of happiness; a good rifle or three, the opportunity and health to enjoy them and good people to connect with?

Todd

RichBratlee · Post by **RichBratlee** » Sat Mar 13, 2004 11:16 pm

Well let's see-- the women have gotten more"mature"-- the cars have slowed down cuz we realize the fast isn't everything and the whiskey--well it's just aged to a perfect mellow for sippin' now and then instead of gulpin"!!

JAGG · Post by **JAGG** » Tue Mar 16, 2004 1:39 pm

Square and round bottom grease grooves also have to do with the bullet sluging up into the chamber and bore ! As one type slugs up more then the other ! I forgot which though ! JAGG

powderburner · Post by **powderburner** » Tue Mar 16, 2004 2:03 pm

how about a square groove and a tapered sided driving band ,holds even more lube ,drops from the mould easy and puts less bearing surface on the bullet

IronSight · Post by **IronSight** » Wed Mar 17, 2004 9:44 am

How about a hollow point which has ejection ports at the bottom of the holler. The hollowed area would act as a soft grease reservoir and eject the grease from the ports into the barrel when fired due to inertia and air pressure. Don't know how it could be cast but i sure wish i had a metal lathe to make a few prototypes!

Trigger Dr · Post by **Trigger Dr** » Wed Mar 17, 2004 12:14 pm

ironsight
Years back Remington did just that with their .22 cal luballoy bullets
Trigger Dr.

Lead Pot · Post by **Lead Pot** » Wed Mar 17, 2004 12:16 pm

Hey IronSight that's a good idea
I wonder if it would whistle like an incoming artillery shell so the guys in the long range pit can duck against the wall. HMMMM good idea:lol:

Kurt

IronSight · Post by **IronSight** » Wed Mar 17, 2004 8:26 pm

Lead Pot,
Whistling bullets!! Never thought of that feature, especially at a 1000 yard range.
The only critical issue would be to precision drill the ejection ports symetrically to minimize any rotational imbalance. And there might be an issue with air jetting out of the ports and causing instability. No problem, as the grease is ejected a small rubber piston which is placed at the top of the bullets hollow will be driven downward and seal the ports.

Trigger Dr. you spoiled my early retirement plans with this patentable idea with the Remington bullets.

By the way, how did they shoot? Did they whistle?

Smokin · Post by **Smokin** » Wed Mar 17, 2004 10:24 pm

Question,

Has anybody figured out if all the lube tranfers from the bullet to the barrel with any of our favorites, or, or, is some left that gets slung off on the way to the target? I gotta think this could be a horse and cart thing. If we get empty before the muzzle=not good; if we have some left over, well, that's a waste of a precious commodity. Smokin (reforming lubaholic)

Lead Pot · Post by **Lead Pot** » Thu Mar 18, 2004 12:22 am

Smokin

I been shooting a lot over snow this winter, and I find a lot of lube in the snow fom about 6 to 18 feet.I shoot a three groove bullet in the .40-70.Even with a two groove .40 caliber it drops lube.

Kurt

Bad Ass Wallace · Post by **Bad Ass Wallace** » Thu Apr 22, 2004 5:08 am

The question of round or square lube grooves is really irrelevent!

Slug your barrel with an unlubed bullet and see what happens to the lube grooves when the rifling displaces lead - it fills them! So after travelling just one inch that lube is displaced into the remaining part of the groove; oops can't fit here so it better just dump in the bore right in front of the chamber.

Now of the remaining lube, it has to be sufficent in volume to coat that bore all the way down that 28, 30, 32, or 34" barrel. Considering the surface area of say 40cal with 50cal and the requirement for lube is in the ratio of surface area inside the barrel which is considerably more for the 50cal. by about 25%.

If the barrel has say 6 grooves & lands of equal size, then in the first inch displaced lead has halved the volume of the existing grooves and what lube remains has to coat the entire bore. This explains to me why bullets with large deep grooves can be shot all day without cleaning whilst shallow design might onlt go 2-3 shots before accuracy suffers.

As a bullet design, I like one with almost square deep grooves with perhaps a 2degree relief for ease of casting BUT as the calibre increases then the volume of grease retained in the grooves has to increase as well.

A lot of shooters are having trouble getting 50cals to shoot accurately and I believe that the lack of sufficent lube is mostly the problem. In my 50/70, the Lyman 515141 doesn't carry enough lube by itself but loading with a grease cookie inproved accuracy a lot. I want to get a Paul Jones mould of about 570gn with deep grooves so I can shoot it without the need for cookies.

ffffgdave@yahoo.com · Post by **ffffgdave@yahoo.com** » Sun Apr 25, 2004 8:24 am

i guess ill be showing my age here. (only 55). . it was published a good while back in the cast bullet mags, that probably are now defunct, that elmer kieth sent the designes for his bullet to lyman to make a mould for his new 44 mag he had just invented.. i believe. of course the exact details being left to my mind are subject to scrutiney.. the bullet came out from lyman with round bottom grooves, easier to make by lyman i suspect.. well ol elmer hit the roof, had a fit and made lyman change the grooves to square bottom.. the reason being as the bullet receives pressure from the base the round bottom, like and egg, is much stronger.. the square bottom will bump up with less effort and lube the barrel better letting it squeez out, or some such or in these parts or whatever.. interesting bit of history tho.. it seem s ol elmer was standing in front of my store on main street in helena montana one day.. a not so good freind took a shot at him in front of the gun shop across the street.. luckily it missed and there is still the bullet hole in the old metal casing in my store front.. the gun store owner told me about it and has the bullet he dug out.. elmer was from great falls, as was charlie russel, great falls, helena, and butte have always had tough guys batteling for some reason or the other ..of course the miners from butte, who when well liquired up were a pretty tough bunch of micks becouse of thier hard life and job that would put muscles every where but thier ears.. ... believe it or not.. dave schlick owner of daves pawn, 437 north last chance gulch helena montana..

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.....round bottom or square bottom grooves....

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square bottom grooves