John Alexanders Request

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Last Post 16 June 2018

CBA Member

45 2.1 posted this 27 October 2016

My quote from another thread in bold blue: “Some of your assumptions about a proper bullet to use doing this have features that are holding you back in the accuracy department, but those are your choice.”

http://www.castbulletassoc.org/view_user.php?id=6375>John Alexander wrote:

45 2.1 -- We only make progress with the open sharing of ideas. That is the real purpose of this forum. Why wait for a PM to reveal your knowledge to one person? We would all like to know. Please be a good citizen and contribute to the forum by starting a thread on the principles of cast bullet design for high velocity. We have a lot of open minded members here who would be interested in such a thread. “I'm a student of dynamic bullet fit instead of static bullet fit.... it makes a big difference. I've done this with one BR rifle and quite a few commercial and customs. If you're interested, you could PM me.”

That sounds interesting. Probably an excellent topic for another thread or at least a good definition of “dynamic bullet fit” for those not familiar with the term.

To avoid completely hijacking mtngun's thread please put your reply on one of the new threads that I hope you will start.

John

OK John, I'll try.... though it hasn't done the least bit of good so far.

I read here about bullet fit.... a static (in rest) fit where most people use a hard alloy and touch or jamb a bullet into the rifling throat. These bullets are Loverin design or a common two diameter Barlow design type..... basically a cylinder with a nose on it that may or may not touch the rifling. As an alternate, we have John Arditos cone in cone throat that achieved some progress. I've noted the records, group sizes and test results posted on this forum. You guys could do a lot better! How?..... Well we're going to discuss that (that is if you all can keep from telling me I'm full of BS and ruining the thread).

I want to hear WHY you think you can't do better and or some good discussion on why you want to do better. Remember, this is John's request.

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Standard Member

Geargnasher posted this 16 June 2018

45 2.1, thank you very much, that's exactly what I wanted to know.

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Standard Member

OU812 posted this 16 June 2018

Gearnasher has the highest post count at Boolits. Seems witty but no help.

Gearnasher,

I apologize for the comment above and I welcome your knowledge...thanks.

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CBA Member

45 2.1 posted this 16 June 2018

Geargnasher wrote: It's not much, but enough to observe clearly when hitting 19 bhn, heat-treated, low-antimony alloy with 45-50K psi loads. I take it that when working up pressure you tend to toughen your alloy before this happens? What puzzles me is in a couple of instances the groups shrink right when the bump starts to happen, IF it happens uniformly. If not, the groups turn to wild patterns.

I don't toughen the alloy, just heat treat it to lino hardness..... good to about 47K. Keep the alloy constituents low and heat treat what little is there. It gives a tough skin and allows expansion.

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Standard Member

Geargnasher posted this 16 June 2018

It's not much, but enough to observe clearly when hitting 19 bhn, heat-treated, low-antimony alloy with 45-50K psi loads. I take it that when working up pressure you tend to toughen your alloy before this happens? What puzzles me is in a couple of instances the groups shrink right when the bump starts to happen, IF it happens uniformly. If not, the groups turn to wild patterns.

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CBA Member

45 2.1 posted this 16 June 2018

About 45% of the rear of the bullet swages down and the bullet foreshortens, the rest has the lands displace the material into the grooves..... they don't bump much if at all as the pressure in the front of the bullet is a lot lower. Verified by recovered bullets from long range testing. Veral Smith has a pressure distribution illustration of base to nose pressures in his book.... look it up.

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Standard Member

Geargnasher posted this 16 June 2018

this may be where you didn't listen, but it doesn't bump, it swages down.... typically, there is 90% bearing with proper alloy and load.

Hmm. I never read that before. What I get sometimes, right when groups start to get good, is swelling in front of the as-cast full bearing surface, where metal flows out to fill the full groove depth. if this swelling isn't uniform all the way around the bullet, I don't get good groups. There is much more bearing surface and rifling marks further forward on the tapered nose of a recovered, fired bullet compared to a bullet which is tapped through the rifle from the breech end with a brass rod. How else can I explain that metal movement except for plastic flow initiated by pressure on the base, resisted by the as-cast bearing surface resisting being swaged through the taper of the throat?

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CBA Member

45 2.1 posted this 16 June 2018

Geargnasher wrote:

Yes, but I was referring to the linotype/long parallel nose/jam fit thing in the autos which will not work with certain actions (the AR-10 comes to mind), not the method used with an extrudible alloy The alloy is extrudible only in the sense it will expand on impart...... but it can be hard and non extrudible also. and a multi-tapered nose which is intentionally bumped to fit this may be where you didn't listen, but it doesn't bump, it swages down.... typically, there is 90% bearing with proper alloy and load. as it engraves by means of the powder pressure. ............................ Are you able to get bullets like the RCBS 30-180 to shoot well at more than the typical speeds in a rifle having a throat such as a SAAMI-spec. .30-'06? Only if they fit properly... which they don't in normal 30 caliber American bores (they are undersize). You can do that in a couple of the European tight bored rifles however.

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Standard Member

Geargnasher posted this 15 June 2018

45 2.1 wrote The virtually impossible part above is wrong. What you stated is basically what is done in a dynamic bullet design. You have witnessed it yourself. BTDT and it works fine in those auto loading rifles as well as many others.

Yes, but I was referring to the linotype/long parallel nose/jam fit thing in the autos which will not work with certain actions (the AR-10 comes to mind), not the method used with an extrudible alloy and a multi-tapered nose which is intentionally bumped to fit as it engraves by means of the powder pressure. If I could work out the bump-fit thing with other bullet designs (like two-diameter sillywet bullets) to have a similar metamorphosis while maintaining concentricity I'd be quite happy, but the poor dynamic alignment due to lack of support in the throat, not the bumping, is the biggest problem getting those to shoot according to the uneven deformities of recovered bullets. Are you able to get bullets like the RCBS 30-180 to shoot well at more than the typical speeds in a rifle having a throat such as a SAAMI-spec. .30-'06?

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Standard Member

JeffinNZ posted this 15 June 2018

Gas checks seem to grip softer alloy better. Your chroni will thank you.

I agree. I shoot 40-1 from my .30-30 at over 1700fps and with commercial GCs get very good accuracy. With a home made aluminium GC the accuracy drops of. The gilding metal GC gives the soft alloy more bite on the rifling IMHO.

Cheers from New Zealand

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Standard Member

Geargnasher posted this 15 June 2018

Jim, it sounds like there are several of us on this thread who are leaning more toward "low tech" these days. Sometimes it's more interesting to learn how to make a factory-built rifle to shoot straight than to become immersed in an equipment race. I have two, heavy benchrest rifles built for my own amusement and edification, but they are test mules for my wild ideas and once it became apparent that heavy barrels and custom, match chambers with immaculately prepared brass only have an advantage in the last few percent, I pretty much quit shooting them. It's also been my experience that selection of alloy, powder, and bullet fit are the areas which do the most for the least regarding accuracy, provided the rifle is put together well enough in the first place. In those areas, I still have a lot to learn, which is why I'm here.

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CBA Member

45 2.1 posted this 15 June 2018

Geargnasher said:

The tight fit of a long, bore-riding nose is not practical for a field rifle, and virtually impossible in an auto-loading rifle, not to mention how the shape hamstrings velocity unless the bullet is cast from a more malleable alloy and matched to a powder which will bump it from behind in such a way that much of the bore-riding portion flows to fill the grooves............

The virtually impossible part above is wrong. What you stated is basically what is done in a dynamic bullet design. You have witnessed it yourself. BTDT and it works fine in those auto loading rifles as well as many others.

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CBA Member

45 2.1 posted this 15 June 2018

Geargnasher said: 45 2.1: Would a very specific example be more helpful?

If you gave sufficient detail...probably!

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CBA Member

Scearcy posted this 15 June 2018

Geargnasher I found your original post to be one of the more interesting I have read in a long while. Thank you for sharing your thoughts.

I have shot CB competition for a long time and I have lost interest in purpose built rifles and bumping dies which are unavailable to the majority of our membership.

If I managed to see past my own biases I thought your preferred (if I can call it that) bullet design sounded more than a little like a modified Loverin design. One of my all time favorite bullets is the Saeco 315 with its stepped taper and short nose. My most successful match loads have come from the Ardito school of thought. That said, I no longer throat rifles and my bump die "machinist" has left this life may he RIP.

Given my low tech leanings I have never found Lino to be very useful for me. Some of my best friends will use nothing but lino, however.

Lately I have been shooting a 243 Winchester exclusively. I recommend this exercise for those who want to make the most of a very limited array of twist rates and bullets choice.

Cheers

Jim

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Standard Member

OU812 posted this 15 June 2018

Gearnasher has the highest post count at Boolits. Seems witty but no help.

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Standard Member

Geargnasher posted this 15 June 2018

OU812: Your methods may work for your purposes but after 20 years of fooling around with the method you describe, it does not work for mine. Bullets cast from linotype alloy tend to slough material off on the driving side of the engraves when fired at high speeds through barrels with typical rifling twists, and further, linotype alloy is an unsuitable bullet material for hunting deer-sized game. The tight fit of a long, bore-riding nose is not practical for a field rifle, and virtually impossible in an auto-loading rifle, not to mention how the shape hamstrings velocity unless the bullet is cast from a more malleable alloy and matched to a powder which will bump it from behind in such a way that much of the bore-riding portion flows to fill the grooves....an action that is difficult to do consistently or predictably without the tough skin of a paper or resin jacket to help keep the front of the nose centered on the land tops while the bumping is taking place.

45 2.1: Would a very specific example be more helpful?

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CBA Member

Ken Campbell Iowa posted this 15 June 2018

i think it is quite normal to "" argue "" when forecasting how cast bullet are supposed to behave ... probably necessary in fact ...

.... but remember that those casterated bullets also have an opinion ....

.... also, it is allowed to pull our own hair out ....but not allowed to pull the other debaters' hair out ...

...except the cast bullet has special allowances and can pull anybody's hair at any time ... probably explains why the smarty pants bullet usually wins these discussions ... or maybe it isn't listening to the debaters ...

ken

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CBA President

John Alexander posted this 14 June 2018

Very interesting discussion of the various approaches to getting a CB started straight.

I think it is worthwhile to try to think through the pros and cons of what may be happening at the start.

The first of CBA four principle objectives as stated in our "Nature and Purpose" is to improve the design, accuracy, and effectiveness of CB ammunition. I believe this type of discussion can further that objective.

Besides avoiding any snarky or self serving posts, I hope this conversation can pick up again supported by the results of firing tests.

To keep things manageable we should state our objectives as gearnasher has. Writing about the best match winning accuracy, with no consideration of power or hunting effectiveness will results in a somewhat different discussion. It is probably impossible to have everything with one approach.

John

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CBA Member

Ed Harris posted this 14 June 2018

Geeeesh... I just read through this thread and thought I was on the wrong forum...

I agree with Ardito's concept of tapered bullet fitting tapered throat and my Accurate designs of cast bullets attempt to fit factory chambers, like this one for the .30-30.

John used very hard alloys because he shot high pressure loads at high velocity, and that's what it took to win.

I used to shoot competition, but haven't for years and have no desire to.

With the cost of replacement barrels and gunsmithing work, I cannot justify spending thousands for rifles which can't do anything else but shoot off a bench. I sold all of my competition gear.

My current interests are shooting cowboy rifles, classic revolvers and military bolt rifles for fun and sharing basic knowledge with those who are interested. I'll leave the prolonged mental masturbatory exchanges to those who find it satisfying, I do not.

If you guys can be civil and chill a bit I might come back to see what else you have written, but I've had enough for now.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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45 2.1 posted this 14 June 2018

First of all, I'd like to address in my own way some of the questions asked by 45 2.1. Why do I think I am where I am and not doing better? Because I haven't mastered the launch....specifically the first half-inch of bullet travel.............. I see you've listened some, but missed some of the other stuff. Most people destroy any chance of real accuracy by the choices and components they choose....and the method they load by.

I believe that a slight mis-match of bullet nose angles to throat angles, allowing a gradual rather than abrupt increase in engraving resistance, is key to getting a bullet straight into the barrel, but do not fully understand exactly where contact needs to happen first and last to best align the bullet dynamically. Any specific input on that would be greatly appreciated. Remember that it is NOT any specific thing, but a number of things you have to do right.... then things happen that wouldn't otherwise. It is NOT an art, but it is science that produces extreme accuracy.