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7br
02-28-2011, 09:01 AM
I was loading up some .41 magnum rounds and I started thinking about the RCBS 41-215 bullet I was loading. This is an older mould with one big lube groove. My LBT mould has two smaller grooves. I am fairly sure the RCBS boolit holds considerably more lube. Neither boolit leads.

Here is my wonderings. What happens when you don't fill the grooves up completely? When the base of the bullet gets pushed to the nose, it would seem that there would not be as much hydrostatic pressure on the lube and might result in gas cutting. This could result in a boolit with more lube leading than a boolit with less lube.

Second thought was the diameter of the groove is quite a bit smaller on the rcbs boolit. Does this aid in allowing the the base to compress towards the nose and squishing the lube better?

44man
02-28-2011, 09:46 AM
I was loading up some .41 magnum rounds and I started thinking about the RCBS 41-215 bullet I was loading. This is an older mould with one big lube groove. My LBT mould has two smaller grooves. I am fairly sure the RCBS boolit holds considerably more lube. Neither boolit leads.

Here is my wonderings. What happens when you don't fill the grooves up completely? When the base of the bullet gets pushed to the nose, it would seem that there would not be as much hydrostatic pressure on the lube and might result in gas cutting. This could result in a boolit with more lube leading than a boolit with less lube.

Second thought was the diameter of the groove is quite a bit smaller on the rcbs boolit. Does this aid in allowing the the base to compress towards the nose and squishing the lube better?
This is 100% wrong thinking! :coffee: The boolit should not deform in any way. A recovered boolit should look exactly like what was loaded except for rifling marks.
Lube grooves are not that important, just fill them up. Boolit style is what will test accuracy.
Your boolit should be large enough for the gun to seal all gas and hard enough to withstand seating, the forcing cone and not skid rifling at the base band.
If a boolit slumps in any way, toss them in the pot before wasting your time. Then make the alloy harder.

Bass Ackward
02-28-2011, 10:56 AM
IHere is my wonderings. What happens when you don't fill the grooves up completely?



It may seem like a lot of things that's why proof of the taste is always in the pudding.

There are different methods of shooting cast where different things happen to make something work or fail.

No single technique covers all situations so no answer is complete. Simple example is a surface lube. How does a surface lube fill anything especialy when you rub it all off, yet you can make that work. Or fail.

So try it, then see if there is anything to theorize over. More fun, less headache.

GabbyM
02-28-2011, 12:31 PM
Have no test to prove it but am sure hydraulic pressure of lube will not stop gas cutting.

Sounds like you’ve been reading up on big lube brand black powder bullets. Where they cut the wide grove deep to weaken the bullet. Cast them of soft lead then kick them with black powder. Black powder guns are often set up quite different than smokeless.

44man
02-28-2011, 03:07 PM
Have no test to prove it but am sure hydraulic pressure of lube will not stop gas cutting.

Sounds like you’ve been reading up on big lube brand black powder bullets. Where they cut the wide grove deep to weaken the bullet. Cast them of soft lead then kick them with black powder. Black powder guns are often set up quite different than smokeless.
Even that is not entirely true. I have picked up hundreds of boolits on the BPCR range and other then impact damage, they look good. Certain boolit shapes can slump at the nose a little but in general BP is easier on a boolit then any smokeless.
That means very soft lead can be used and is actually preferred.
Most lube is spun onto the bore by centrifugal force and the thrust forward of the boolit.
More and better lubes are needed because of the amount of fouling that has to be kept soft for the length of the barrels.
Cartridge rifle shooters use large diameter boolits for the bore. They do not want slumped boolits either.
Boolit shooting muzzle loaders are strange puppies and I have proven a thousand times that a tight fit at the muzzle is better then a small boolit depending on base expansion. My feeling is that seating a tight fit will push fouling down to the powder as long as a good lube was used. That leaves the bore in better shape in front of the boolit. That fouling is then shot out.
A small boolit like a Minie' ball will have the base expand but I do not think that will clean the bore ahead of it. Fouling will build badly. We have increased accuracy and the amount of shots without cleaning by lapping Minie' molds for a tight muzzle fit. I have turned muskets that would not hold a 3' target at 50 yards into one that clangs gongs at 200 meters by just lapping the mold. It would seem even with cleaning between shots, the under size Minie' never expands evenly or grips rifling good enough.
Anyway, everyone has opinions like the thing between your cheeks, everyone has one and I am no different. [smilie=l:

7br
02-28-2011, 03:45 PM
I do my best to fill lube groove to capacity and am not suggesting that it is a good idea not to. Just wondering what effect it would have. As for the boolit not deforming except for the rifling, I would have to disagree. Might not deform much, but you don't push a +.001 slug down the barrel without some deformation. I would imagine that the barrel deforms some too, but springs back rapidly. Come to think about it, the chamber flexs because strain gauges work on them.

Also, once the boolit leaves the barrel, it is no longer under pressure. Not sure how much spring back there would be at least a little. Might have to ask one of the materials guys around here. Shooting my .41 gives a base area of .132 sq in. If I am running at 15K psi, that puts about a ton of force against the base of the boolit. I would think that might alter it a bit. Add to the fact that there is a big chunk of metal missing where the lube groove is and I could definitely see the groove getting shorter.


Hmm, lots o stuff to ponder. Probably does not make a hill of beans difference though.