Square lube groove vs rounded - pros and cons

[Three-Fifty-Seven]

[Char-Gar]

Years back, Paul Matthews, a cast bullet maven, designed a bullet with long but shallow lube grooves, thinking this might be better than longer and deeper grooves. The amount of lube stayed the same, just the geometry of the groove where it was contained. He wrote up his results in Gun Digest.

I have been many years but my memory tells me the results were the long shallow grooves performed not as well as the traditional deeper but narrower grooves. This gives credence to the notion that a bullet collapses to pump out the lube. The shallower grooves gave a thicker and stronger bullet that did not collapse to pump out the lube.

Like I said, it has been many years back, but that is my memory on the subject.

[Oreo]

What's interesting to me about this compression pumping theory is what's to stop the alloy from flowing unevenly? Why don't we (or do we?) see boolits recovered with un-square bases? If it happened it certainly must be awful for accuracy.

[45 2.1]

What's interesting to me about this compression pumping theory is what's to stop the alloy from flowing unevenly? Why don't we (or do we?) see boolits recovered with un-square bases? If it happened it certainly must be awful for accuracy.

If your interested in the un square bases concept, use a recovery box for an undamaged boolit to look at. The easy way to test this is long range groups...................

[Cap'n Morgan]

If you really want to recover boolits with nearly no damage from being stopped and all the deformation on them being from the trip down the bore. Fire them into a snow drift. Not a big ice berm piled up by a plow, a natural blown snow, powdery snow drift and then recover them. That is the best medium I have ever found to stop a boolit, even one fired from a high powered rifle at high velocity without damaging the boolit in any detectable way. Be prepared to shovel and sift through a lot of snow and have a big snow drift to shoot into. Penetration to stopping depth is measured in feet or even yards.

F. W. Mann found, almost by accident, that sawdust, mixed with oil, would stop a bullet without any visible damage. If dry sawdust was used the bullets would flatten on impact, and while wet sawdust would lessen the damage, for optimum results the sawdust must be saturated with light machine oil. The bullet would often penetrate as much as four or five feet before stopping, so it would take quite a large amount of sawdust and oil to replicate this. Still, it should be easier than finding a snowdrift in July...

[Char-Gar]

What's interesting to me about this compression pumping theory is what's to stop the alloy from flowing unevenly? Why don't we (or do we?) see boolits recovered with un-square bases? If it happened it certainly must be awful for accuracy.

I really don't know if the pumping thingie is real or not. It may or may not be. But what I do know is the base of a bullet had better be flat, square and parallel to the muzzle at it exits or the escaping gas will push unevenly on the base as it exits the muzzle and that is not good for accuracy.

I also know that bullet compression inside the barrel will vary with alloy, burning rate of powder and total amount of pressure. To much compression and accuracy goes south. That is the reason why fast powders like 2400 begin to loose their usefulness after about 1.8K fps and slower powders do better. A bullet that is shoved down the barrel suffers less compression than one beated down the barrel with fast powders.

[Alan in Vermont]

........... less than 1.25 MOA at 385 yards at about 2400 fps for group cores

What I want to know is WTH is a "group core"? Do you get to pick what constitutes the "core"?

[Char-Gar]

What I want to know is WTH is a "group core"? Do you get to pick what constitutes the "core"?

I would guess a fellow would just measure the bullet holes bunched up and disregard those outside this core, but that is just a guess. If I am correct, this kind of scoring in not allowed in any form of competitive shooting I know of. We all have fliers and shots called out, but those count in score and group size. Like you I await the answer.

[Alan in Vermont]

WOW!, once again I have learned something from this group. I can now shoot tiny groups with the best of them, just claim the hits I want and disregard the others. That's a good way to get sub-MOA groups out of some old clunker that is hard pressed to shoot minute-of garbage-can.

I have to admit to disregarding shots I call "out" when I'm working on loads. But, if I didn't call it as a bad shot it stays in my results. I just can't see lying to myself to try to impress anyone.

Now if I could just find that can of "Internet BS Repellant" that I know I have around here somewhere,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

[Alan in Vermont]

If your interested in the un square bases concept, use a recovery box for an undamaged boolit to look at. The easy way to test this is long range groups...................

Doing that, would you judge that the ones with out of square bases would be the ones outside your "core" and be irrevelant?

[Jailer]

Turbo1889,

Care to share what you found from shooting into snow? We don't get much down our way!

Well I'm not Turbo1889 but I'll share. He's right, it is the best to recover fired bullets with no impact damage.

These were shot from a Glock 21. You'll notice on the TL boolits 2 distinct things. Evidence of skid and gas cutting at the base. This was a few I fired in the winter while I was first casting and figuring things out.

[DrCaveman]

Jailer

Those are interesting. Without unfired boolits to compare, im not totally sure, BUT, it appears that the lube groove in your TC boolits is about the same length as it was when cast. So, at 45 acp pressure, i guess the compression/deformation isnt happening.

On the other side of the coin, it seems that extreme deformation is happening with the tumble lube design. Was there a big accuracy difference?

Is that residual LLA on the nose of the TL SWC? If so, i guess lee's claims about its durability are validated.

That is the best photographic documentation of polygonal rifling impressions that i have seen. I trust there was no significant leading?

[45 2.1]

Doing that, would you judge that the ones with out of square bases would be the ones outside your "core" and be irrevelant?

Ya know, I just love the sniper mentality here. If you don't like something, just assassinate it or them by saying cute witticisms. We have quite a few people on this forum that do that regularly. If you really don't understand what is talked about a nice direct question without the gas would do. You need to talk to some of the long range black powder cartridge shooters. Ask them what happens to their shot when a strong gust of wind coincides at the instant the trigger is pulled, especially when they are testing loads and rifles....they will know and most would be able to tell you about where it should be on the target. Most folks here don't shoot far enough away to know what wind does to lead and they certainly can't shoot long range lead HV and have a small set of holes with one out due to windage.

[swheeler]

What I want to know is WTH is a "group core"? Do you get to pick what constitutes the "core"?

I believe this is the kind of group scoring used by an x-member here for his famous 6.5 Swede at high velocity. When you just pick those shots that hit closest to each other you never see the effects of rpm's, therefore it doesn't exist and all your groups are sub moa it's core alright, rotten to the core.

[Char-Gar]

Long range shooting is a very flexible term. What is long range for some is not for others. I cut my teeth shooting 4 position high power in local, state and national competition. Ranges out to 600 yards were the norm. I did some 1,000 yard shooting as well, but not as regular fare. This was done with 03 Springfields and later National Match Garands. This is just to say, that I for one have a reasonable understanding of what is involved in shooting at longer ranges. I am certain that are others here, whose knowledge and experience far exceeds mine.

I do know that we were not allowed to shoot "core groups" and to disregard shots outside of the central cluster. Every shot counted then and still does now. This does not change.

How a fellow wants to evaluate and measure his own personal groups is his business...until...he comes to places like this and claims to be able to do something others have been unable to do. The next step is to claim superior knowledge and wisdom, without full disclosure of how his stats are arrived. If we all used the same methods of measurements, then perhaps he would have something to offer. If I only reported "core groups", then I also would appear to have superior knowledge and shooting skills. But to do so would be to misrepresent my knowledge and abilities.

Another thing that never changes is the odor of BS. It is very recognizable to the nose and to the eye when it appears in print. Perhaps folks should just allow it to pass and not call a foul on it, but perhaps not. There is continual influx of new shooters and new people on this and other boards and they should be able to depend on straight information to help them along the way. Nonsense and ridiculous claims all to often create false expectations and send them down the wrong path. This is not good or helpful to anyone.

Therefore my motivation for threads such as this, is not who knows more and who knows less, but maintaining a reasonable standard of honesty and reliability so that others may progress in their casting, shooting and loading. This does not make me popular with some folks, but that is just the price I will have to pay. Nobody unhappy with me is signing my paycheck

[swheeler]

A person has to learn to seperate the oats from the chaff on these forums, and yes, recycled oats does have a certain smell to it.

[Southron]

If you ever recover any of the cast bullets you have fired, you will note that there is still a lot of lube left in the grease grooves of your fired bullets. Apparently, it takes very little lube to adequately lubricate a bullet as it flies down the bore of your rifle or pistol.

Square VS Rounded grease grooves? I have never been able to tell a difference between the way they cast and shoot, so the actual shape of the grease groove is most likely a moot point.

I met Elmer Keith back in the mid-1970's and he was truly a "Larger Than Life" character. I think he was suffering from some type of age related dementia when I met him because his short conversation with me was rather confused. I was very nice and respectful to him. The man accomplished a lot in his life and I realize that sooner or later, if we are lucky, we all get old.

[Char-Gar]

If you ever recover any of the cast bullets you have fired, you will note that there is still a lot of lube left in the grease grooves of your fired bullets. Apparently, it takes very little lube to adequately lubricate a bullet as it flies down the bore of your rifle or pistol.

Square VS Rounded grease grooves? I have never been able to tell a difference between the way they cast and shoot, so the actual shape of the grease groove is most likely a moot point.

A good discussion, with no agreement can be had about just what cast bullet lubricant does. Many will posit that "lubricant" is a misnomer and it has little to do with lubricating the bullets path down the barrel, but forms a seal at the base of the bullet to keep the fire off of the sides of the bullet. The actual lubrication of the bore being very much a secondary function.

To be truthful, I really don't know what it does. I know what works and does not work, but I don't know why. I doubt if most of those who feel they know truly do, but rather advance theories and repeat what others have said. It must do something because it is needed in most instances. Note, I said most and not all.

I think I will go over to Cast Bullet Association board and ask Ed Harris what is the purpose of bullet lube. His is an opinion I would take pretty much as gospel.

I met Elmer Keith back in the mid-1970's and he was truly a "Larger Than Life" character. I think he was suffering from some type of age related dementia when I met him because his short conversation with me was rather confused. I was very nice and respectful to him. The man accomplished a lot in his life and I realize that sooner or later, if we are lucky, we all get old.

Like most people who suffer strokes, Keith had several smaller ones before he had the big one that pulled the pins out from under him and put him in a nursing home where he was until he died. I met him back in the mid-60s when he was still hitting on all eight cylinders.

[Jailer]

Jailer

Those are interesting. Without unfired boolits to compare, im not totally sure, BUT, it appears that the lube groove in your TC boolits is about the same length as it was when cast. So, at 45 acp pressure, i guess the compression/deformation isnt happening.

On the other side of the coin, it seems that extreme deformation is happening with the tumble lube design. Was there a big accuracy difference?

Is that residual LLA on the nose of the TL SWC? If so, i guess lee's claims about its durability are validated.

That is the best photographic documentation of polygonal rifling impressions that i have seen. I trust there was no significant leading?

There was leading with both of those designs because they were sized too small. And yes that is LLA left over on the nose and in the grooves in the SWC. The TC boolit is not deformed in any way. If it weren't for the rifling marks you swear it could be lubed and shot again.

[Alan in Vermont]

You need to talk to some of the long range black powder cartridge shooters. Ask them what happens to their shot when a strong gust of wind coincides at the instant the trigger is pulled, especially when they are testing loads and rifles....they will know and most would be able to tell you about where it should be on the target. Most folks here don't shoot far enough away to know what wind does to lead and they certainly can't shoot long range lead HV and have a small set of holes with one out due to windage.

I do know what happens when you get caught by the wind, it ends up a 9 or an 8, or it blows a really sweet group. I also know people who claim fantastic results, to the point of being beyond the laws of probability. A MOA rifle may be able to cut a one hole group, if you shoot it enough, but it's about impossible to shoot them on demand.

You never did explain your "core group". What is the criteria that makes a shot outside the core? How much of that determination is based on how badly you need an impressive number? There's a lot left to the ethics of the shooter when you start a process that allows picking and choosing which shots count.

Lacking any firm criteria I have to think that some of your claims are not so amazing when one considers the amount of smoke(screen) you have to overcome.