Shiloh Rifle Forums

Question for grease groove shooters....

Has anyone spent time comparing bullet molds with square bottom (90 degree cut) lube grooves versus bullet molds with radiused bottoms or molds with angle cut lube grooves? In other words, absolute square grooves against angle cut grooves?

Is there a consensus, or even a strong opinion one way or the other?? It seems like the absolute 90 degree cut grooves would not lube near as well, but maybe my reasoning is off-base.....

Thanks!!!

With all the time we spend thinking and discussing the various minute details of BPCR. I don't recall much time spent on that item. We do have opinions on large grooves vs. mini grooves but that's about as close as I know of. Seems like a worthwhile topic but I'm still trying to figure out how to break good shots every time.

Bryan

My own opinion on lube grooves ........ I think that lube grooves are not so much to hold grease, as to prevent gas leakage past the bullet, which as we all know, is the cause of leading, not so much a lack of lubrication. In other words, the grooves full of grease act as O-rings. FWIW.

CHRIS

I ask because I was reading through this today.....

http://www.lasc.us/lubeingredients.htm#oliveoil

and then I went to the chapter in his book on lubes, and he had mention in there about round bottom vs square bottom grooves and how a bevel-cut groove might assist in better lube flow....

I'm thinking about maximizing lube efficiency here primarily.....

Glen is a smart cookie, retired nuclear chemist who loves cast bullets and old guns.

I've always thought it makes sense to pre-lube ones bore with a patch loaded with the same lube that is on the bullets to grease the skids before the first bullet passage.
As to groove profile I've read it speculated that square based grooves resist bullet compression better than radius grooves do . They do for a fact hold more lube volume than do radius grooves and the speculation is that the lube supports the groove from initial inertia compression of the lead alloy.

The way I read Fryxell's text was that the huge square bottom lube grooves were beneficial to Keith because he had only one of them...On our rifle bullets, we have room for several lube grooves and thus can spread out the lube over a large area and negate the need for the big square bottom. Also, I got the idea that he was inferring that a bevel cut (or even round bottom) lube groove offered superior lube efficiency...meaning that more lube would be deposited in the bore versus the pure 90 degree lube groove which would tend to scrape the lube off and keep it in the groove...

I've read elsewhere here the idea of "just enough lube"...I'm guessing that the idea behind that is that the lube is almost all deposited in the bore and only a small amount remains when the bullet exits the bore...is that right?

Thanks for humoring these questions...I'm just one of these A-holes who always has to know "why"...(it was a tough thing to live with when I was in the Marines LOL...)

That depends a lot on temperature and lube make up, it looks like to me. I find hand gun snow bullets quite often with what looks like almost all the lube still in them.

Dan Theodore used to say the best thing the big deep grooves did was it helped the lube makers sell more lube.
Keith Lay

Would inertia push lube back and out easier with wide shallow groves?

Seems if you’re finding bullets with most of their lube intact that would have to be considered a failure as far as lube goes…

In my smokeless loading, I use White Label Carnauba Red and always thought it was a good lube. I pay attention to my bore size and cast/size my bullets accordingly and I thought that was it.

Now that I’m shifting gears and looking to up my game I’m questioning these old assumptions.

How could you test lube without recovering the bullet? One idea would be to take a piece of concrete form tube about six feet long from Home Depot and line it with white butcher paper. Prop it up on sawhorses and shoot through it. Pull the paper out and examine it for lube chunks. Probably want to use the old 15 grains of Unique load for this so you don’t have a bunch of powder residue in there…

The better lube and lube grooves would leave less on the paper? Maybe an even dispersion pattern close to the muzzle would indicate that the lube was liquified and then spun off the bullet easily? Perhaps bigger chunks could mean that the lube was being flung off the bullet in an irregular fashion?

Seems like trying this would be cheap anyway…

One way to tell if your lube may not be doing it's job is look at your chronograph ,you know the kind where you shoot through the triangles. If it's covered in lube it may not be working so good although I do think it's a good thing if you see a lube star on a muzzle. I have had better success with "mini-groove" type grooves. I saw a a "shadow-graph" somewhere of a .308 Winchester bullet and you can see a little shock wave where just the canellure on the bullet is putting out it's own little shockwave. Now imagine what one of those multi-grooved large grease groove bullets is doing. Theoretically to me it would seem that the smooth paper patch bullet should have an advantage here but I never could get the PP bullets(although I got them to shoot pretty darn good) to stay with my GG'ers despite several years of testing.
Keith Lay

That's true but the big chucks flung off indicate post barrel expulsion and I'm not sure how much we can learn from that.
I think it actually takes far less effective lube volume to get the job done than we have previously thought which is pretty much born out by DT's mini groove designs which I think were all flat bottomed , no?

It’s possible that the volume of lube needed could indeed be a lot less than previously thought.

As far as the bottoms go, Fryxell didn’t really differentiate between them and the rounded ones, I think he was looking more at the sides of the groove…I think that he thought the 90 degree cut sides would be less effective…I might be reading things wrong though…

Only way to test that would be two molds identical except for the grooves…one with totally square grooves and one with angle cut grooves…

It would be interesting to capture some oiled saw dust or snow bullets and measure the groove depth and width after firing. We often measure for OAL but I've not thought to check what the grooves measure after a trip up bore.