What Role Does Centrifugal Force Play in Lubing the Bore?

[Silver Jack Hammer]

Yesterday I was chronographing some loads at the public range and big 'ol wad of lube landed right in the middle of the screen where the "0" is displayed. Under the artificial lighting I couldn't tell if my chronograph was reading "0" or "8".

Then I got to thinking about how boolit lube lubricants the bore. It had been my impression from reading what others have written that lube works by compression of the boolit. But really, wouldn't centrifugal force play a bigger roll?

Recently I have taken up shooting at close range, 7 yards, and lube is splattered on the target, apparently from centrifugal force. So wouldn't centrifugal force play a part in Lubing the bore? How much of a part does centrifugal force play in Lubing the bore than boolit compression?

I'm shooting a Colt .45 SAA with RCBS .45 270 SAA cast 4 parts Linotype and 6 parts plumbers lead. Sized .454" lubed with Alox over 8.0 gr of Power Pistol. Winchester cases CCI300. I've been casting for years and my cast boolits make cleaning after shooting a breeze. Not leading what so ever unlike store bought boolits.

My close range shooting consists of drawing and firing usually at playing cards at about seven (7) yards.

[btroj]

Not much, at least in my opinion.
I have found lube boogers on targets at 100 yards with some lubes. If the lube is still flinging off the bullet 100 yards down range how much do you think it flowed/moved due to bullet spin in the bore?
Look at bullets recovered from berms lubed with hard commercial lubes. The lube is still in the grooves in many cases. Again, how much flow occurred in the lube due to bullet spin?
In lube testing some of use fired at a piece of paper only a few feet in front of the muzzle. This let us see if the lube is flung off in little bits or as more of a wet spray. In one case it was possible to determine the number of barrel grooves based on lube splatter on the paper.

This is an area where lots of questions remain. What does a lube do in the bore and how does it work? I sure don't have all those answers.

[Silver Jack Hammer]

Commercial boolits with hard lube leave me with a chore scrubbing lead deposits out of the bore where my cast boolits with Alox don't leave any lead deposits. After shooting hard lube commercial cast boolits I don't see any lube on the patch when cleaning the bore. After shooting my Alox lubed cast boolits I see a good amount of lube on the patch after running it through the bore.

However lube works, Alox works better at the velocities and rate of twist I am shooting with a .45 Colt than hard crayon lubes used by the commercial outfits.

[John Boy]

Silver Jack: The hardness & quantity of lube used is a determining factor whether the bullet will be naked out the bore or not. To properly lube a bore, only a thin layer of lube is needed. Yes, I've had target holes at distances longer than 7 yds

Here is a bullet with lube still in the grooves that I dug out of a 1000yd berm. A major part of the lube formula was paraffin ...

[freebullet]

Interesting...I've noticed lube buggers on paper. Looked like someone sneezed on the target. It must not have mattered much at 15yd as they were shooting into 1 hole. That was with srh454 300gr hp about 1100fps.

[popper]

I got to thinking about how boolit lube lubricants the bore. It had been my impression from reading what others have written that lube works by compression of the boolit. But really, wouldn't centrifugal force play a bigger roll?

Depends. What is the lube weight in a groove & RPM in the bore? How stiff a load needed to compress the L.G.? How much lube gets wasted by 'blow by'? What is viscosity of lube? How much 'excess' lube that is not really needed? No fixed answers.

[hpdrifter]

I suspect everything in the mix is important.

Investigate labyrinth seals on shafts.

[geargnasher]

Muzzle blast has as much to do with pistol bullets splattering lube everywhere as does the fictitious force.

Popper, you pretty much said it.

Gear

[therealhitman]

A centrifugal effect would be based on the lube's density and distance from the axis of rotation. I would think that it's G-force number would be considerably less than the sudden stop of shooting a lubed boolit into a stack of Brownell's catalogs with a wrist rocket. And the lube does stay in the grooves, I just tried it with a .452 200gr SWC. Not very empirically scientific but somewhat helpful towards relative comparison.
Hey, what can I say? It's my day off and my 12 yr old turned it all into a fun game of Mythbusters lol.
Bad science aside, I still believe the adage that hydraulic action from grooves are the main driver for hard lubes migrating. With really soft alox stuff I would think heat is an additional motivator.

Attachment 158562

[randyrat]

Here is some good reading on this subject...Glen says there are 3 things and Centrifugal force is one of them once the rotation of the bullet starts
http://www.lasc.us/FryxellLubeCastBullets.htmm



My little tinny 2 cents worth of a thought is; we use too much lube most of the time.

[BAGTIC]

Very little. I began ignoring it when I kept picking up fired bullets from the berms with lube still intact after impact.

[JSnover]

I'm sure it means something, though I don't think it means much.
Ideally the grooves are full and the bullets are sized 1 or 2 thousandths over groove. Hydraulic pressure caused by compression would work the same way in a smoothbore; forcing the lube out against the barrel despite the lack of rotation. Those recovered bullets tell me that in most cases only a small about of lube is able to get between lead and steel.

[gwpercle]

If lube is splattering the target, I would try a little less lube and see what happens.
Somewhere I read that you don't have to fill all the grooves, excess lube just gets flung off between muzzle and target. Or on the target. Unless it's a hard lube and that stuff just stays stuck in place.
Try not to overthink this stuff....it will make you gray haired and wander around talking to yourself .
Gary

[DougGuy]

Gary ^^^^ LOL so true..

I almost never recover boolits with Felix or SPG on them except a minute amount in the gas check flange. I look at it this way. If I run a clean patch down my SBH bore after a shooting session, it comes out black and waxy greasy with occasional bits of unburned powder and also powder residue mixed in. This shows me what was in the bore waiting for the next boolit to come scooting through there, and as long as the bore is remaining "seasoned" like this between shots, the lube is doing exceptionally well, it shows that it is lubed before, during, and after shooting. What more could you ask for? Who cares what flings off in front of the muzzle?

[runfiverun]

well the guy trying to shoot a 1/2" group at 2400 fps cares for sure.
I use as little actual 'lubricant' as I can get away with.
whether that's by volume or by decreasing the content it's how I roll.
lube needs a friction component and flow characteristics to survive the trip down the barrel, once it gets there it's job is over.
it not being in the grooves creates waves of air to flow around the boolit differently than if it's there.
so it either all goes or it all stays anything other than that will affect the flight of the boolit.

[Bigslug]

I think it ends up being far more about compression.

The boolit is getting squashed from the front, the rear, and the sides, and the lube ultimately has to go somewhere, right?

Well. . .since the boolit is in all likelihood sized .001"-.002" OVER the bore diameter, there really isn't a lot of space for the lube to move to. Yes, there are those bore variations and potential for gaps caused by torque on the slug from the rifling, but ideally, these don't amount to very much - - indeed, a lot of our casting technique and gun prep are geared toward minimizing/eliminating them. So I tend to think that compression is sufficient to the task of filling those minuscule gaps as they occur. I'm also drifting more to the camp that says our groove filling materials aren't serving so much as "lube" but rather "gasket material" or, to put it another way "ablative piston rings". If your fit is good, bore straight & smooth, and alloy hardness correct, you probably aren't going to be using much lube.

My own target observations suggest (to me anyway) that the centrifuge effect is not all that great. A major objective of the Quest thread was to enhance accuracy by creating a product that would reliably flip off immediately on bore exit - indicating that lube NOT doing this is a common issue. I have witnessed lube boogers splattered on 100 yard rifle targets, so obviously the suddenness of separation is quite variable. We tend to be in awe of the massive RPM numbers we see listed with rates of bullet spin and naturally think "that's got to generate a helluva lot of outward-flinging force", but remember, the lube is pretty close to the "hub" of the "wheel". Ask a handy physicist for confirmation, but I'd bet a 26-27" racing bicycle tire has more outward-flinging force at racing bicycle speeds than a quarter to half-inch cylinder that's literally shot from guns. If a ring composed of wax and axle grease can stay together with fair reliability through the event, there can't be much going on there.

[randyrat]

Run5run I have also experimented with smaller and smaller amounts of lube and found out how little it takes.. I also have used splatter sheets in the shooting lane to see how long, if any lube, stays on the bullet. I'm not into the LOOOONG range like some are, but anything to help with accuracy for me is a good thing, God only knows.

What percentage of each of the 3 mechanisms that work on lube, I don't know..But I can imagine all three do contribute.

It has to be some real hard and sticky lube to stay on after exiting the barrel..I like a lube to be balanced, one that won't go for a ride down range and one that RPMs do help make it go away.

[BAGTIC]

When one picks up a fired bullet and finds some but not all of the grooves containing lubricant what does that prove? Did the missing lube come off at impact or was it shed between the muzzle and the target? If every bullet did not behave identically would not that effect the gyroscopic stability and accuracy? What if 1/2 of a groove was full of wax and the other half empty? Why do shooters fire 'fouling shots' before competition? What would we do if we did not have something to blame for our 'flyers'?