Cast bullet velocity limits?

[swheeler]

Yup, most mentioned have 14" or 16" twist with possibly a 12" twist with the .223. Do the math (including for the '06 with a probable 10" twist) and we see all of them are losing accuracy right 140,000 RPM or slightly before with regular alloys and regular cast bullets. I wonder why that is......

I conducted a high velocity test today that demonstrates how the adverse affect of increased RPM becomes noticeable and very evident. Recently I switched from M118 match cases to fire formed WW Palma cases. With the thinner WW cases there was greater case capacity and I was able to comfortably get 50 gr of AA 4350 under the 311466U bullet cast of 80/20 linotype/Pb, AC’d, sized at .311 with the 1st 2 driving bands at .300, lubed with Javelina and Hornady GCs squarely and firmly seated on the bullets GC shank. These bullets were from a Lyman 4 cavity mould and other than a visual for defects are non-selected or weighed. Fully dressed they weigh in at 155 gr.

Previously, on several occasions, accuracy with the M118 cases and 59 gr AA4350 ran right at 2600 fps and gave very consistent 10 shot group accuracy of 1.5 moa. The RPM for that load is 133,714 with indications it was on the ragged edge of the RPM threshold at that velocity. Thus with the increased capacity of the WW Palma cases I thought perhaps I might be able to push it past it’s RPM threshold. With the 50 gr AA4350 load the 311466U was pushed to 2678 fps, a gain of 78 fps +/-. The RPM of the faster load was 137,725. Here’s what happened with the testing completed today.

1st target is 10 shots at 100 yards. The velocity was 2678 fps with an SD of 13 and an ES of 43 fps. Average peak pressure was 38,700 psi(M43) with a SD of 600 psi and an ES of 1,900 psi(M43). From an internal ballistic standpoint that is a very uniform load. The Oehler M43 Data sheet is included for DrBs benefit as he likes “data”. Terminally (on target) the results showed some of the shots had exceeded the RPM threshold and were “flings”. I have to admit here that in all my shooting career and study I have never before heard “flyers” referred to as “flings”. But if the good, educated DrB wants to call them "flings" it’s ok by me. Anyways, on target, the 3 top shots strung vertically were the 3 highest velocity shots of the test string (I do track such) and as such also had the highest RPM. The 7 shots that had the lowest RPM/velocities went to zero and grouped within the expected 1.5 moa (1.36 moa to be exact).

Those 3 flyers (flings) indicates that when tested at 200 yards with a 10 shot group a probable 3 shots, or about 30%, would give non linear group dispersion and those shots would be out of the group. Linear group dispersion should be about 3” at 200 yards for 60 – 80% of the shots which shouldn't have exceeded the RPM threshold. I then put a target (“A” Decimal) at 200 yards and continued the test with a 20 shot group. The 1st five shots on the target were the 3 at 6 o’clock in the 10 ring, one of the 6 o’clock Xs on the line and the shot cutting the line in the 10 ring at 3:30. That group showed 1 flyer (fling) out of 5 shots with the 4 shots going into normal group dispersion and the flyer (fling) being non linearly out of the group. I move the scope elevation up ½ moa and continued with the remaining 15 shots.

As we can see on the target 10 of the remaining 15 shots went to group with a linear group dispersion of 3.18”, just as it should have. However, 5 of the remaining 15 shots did not go to group, were flyers (flings) and show definate non linear dispersion. We see a wide, non linear dispersion of those 5 flyers (flings) plus the flyer (fling) from the 1st 5 shot group prior to sight adjustment and should also notice how all the flyers (flings) demonstrate an almost perfect radial dispersion well out of the group. Many times such adverse accuracy affects are not noticed when we use an insufficient sample size such as a 5 shot test string. However, with a sufficient sample size such adverse affects become readily apparent.

As I surmised from the 100 yard target exactly 70% of the shots went to group and 30% of the shots showed definite non linear group dispersion. Total group size is 7” adjusted for the ½ moa sight change. Thus we see that those flyers (flings) do indeed tell us something but without adequate testing we may not understand the “what” that they are telling us. I do find 2678 fps quite with such accuracy to be intriguing and may heat treat those bullets to see if that might push the RPM threshold back above the velocity capability of this load. As of now though, the realistic velocity without exceeding the RPM threshold for this bullet/powder combination would seem to be around 2625 fps. That way, on a hot day, the RPM threshold should not be exceeded and accuracy should remain constant at 1.5 moa or less.

BTW; I just cleaned the barrel and not one spec of leading was found.

Larry Gibson

Larry: thanks for taking the time to post your results, much appreciated by many including myself I'm sure. Just goes to show what 80 fps can do to groups when you are approaching the threshold. I am one of those guys that has always liked targets(or a least pictures of targets and especially 100 and 200 yds) as opposed to 50 yd targets, graphs and charts, that's just me.
Looks like a 14" twist 308 is on my todo list, a 155 gr @ 2600 fps and 1.5 MOA sounds fun. I'd guess your alloy is about 18 bn and the 4350 should just be cleaning up , just the facts mam, remember Dragnet?

Larry I think you made a ten grain typo up top. Thanks again Scott

[badgeredd]

I have further testing to do but I am finding that an alloy that is in part a babbitt that contains a fair amount of copper seems to be strengthening my alloy significantly. This strengthening seems to be allowing considerably higher velocities with very good accuracy. It is my opinion that one can quite easily exceed 2400 fps and still have very good accuracy with the right alloy and still maintaining fit, sizing and lube relationship.

Edd

[Larry Gibson]

Larry: thanks for taking the time to post your results, much appreciated by many including myself I'm sure. Just goes to show what 80 fps can do to groups when you are approaching the threshold. I am one of those guys that has always liked targets(or a least pictures of targets and especially 100 and 200 yds) as opposed to 50 yd targets, graphs and charts, that's just me.
Looks like a 14" twist 308 is on my todo list, a 155 gr @ 2600 fps and 1.5 MOA sounds fun. I'd guess your alloy is about 18 bn and the 4350 should just be cleaning up , just the facts mam, remember Dragnet?

Larry I think you made a ten grain typo up top. Thanks again Scott

Scott

Thanks, you were right about the 10 gr error....it's corrected.

Larry Gibson

[Larry Gibson]

I have further testing to do but I am finding that an alloy that is in part a babbitt that contains a fair amount of copper seems to be strengthening my alloy significantly. This strengthening seems to be allowing considerably higher velocities with very good accuracy. It is my opinion that one can quite easily exceed 2400 fps and still have very good accuracy with the right alloy and still maintaining fit, sizing and lube relationship.

Edd

No doubt about that. I've considered adding the babbit but I was hoping for a hunting load with an alloy of around 18 BHN that was still somewhat malleable. Scott was right on the money with the BHN on my Lino/Pb at 80/20 BTW. When I go back to the 225107 in the .22 Hornet I will be adding some babbit to the alloy. I see no reason a 2700 - 2800 standard cast bullet Hornet load out of a 14 or 16" twist barrel shouldn't shoot as well as Jacketed at the same velocities.

Larry Gibson

[nanuk]

would adding copper make the boolit less maliable, more brittle?

I remember (303Guy?) someones comments about using MAPP torch to melt a GasCheck into a melt to add copper....

[badgeredd]

would adding copper make the boolit less maliable, more brittle?

I remember (303Guy?) someones comments about using MAPP torch to melt a GasCheck into a melt to add copper....

My experience has shown that with a good balance (tin to antimony) with a copper enhanced babbitt will toughen a boolit. In using a blend of tin, babbitt, pure lead, and lino one can get a rather hard but still malleable alloy that is not brittle. It won't mushroom in the classic jacketed bullet style but it may rivet. Why the babbitt seems to toughen the alloy and tends to take away brittleness is beyond my understanding at this time. It's my opinion that when one is hunting with a 35 caliber boolit and larger, one really doesn't have to be terribly concerned about expansion if one has a decent meplat on his/her boolit. Because I live in an area where I can't hunt legally with a 30 calibre cartridge in my contender or use a rifle on deer, I can't honestly speak to anything in a hunting situation below 35 caliber. I can however say that a 35 calibre boolit in the 22+ bhn area will definitely put down a deer with authority if it drives through or penetrates deeply without breaking up. The babbitt seems to help in controlling the break-up part of the equation.

As far as accuracy is concerned, driving a 30 calibre above 2350 fps with the right alloy and still get good accuracy is definitely do-able. At a local get together one forum member was pushing a 238 grain cast bullet out of a 1-9 1/2 twist barrel at a measured 2386 fps with 1 1/2" repeatable groups at 100 yards as witnessed by four other forum members. This was from an old battle rifle. As is often said on this forum, a lot of the old "rules" can and are being proven to be inaccurate with some experimentation.

Edd

[Larry Gibson]

+1 on what badgeredd said.

The addition of copper making a lead/tin/antimony/copper alloy does indeed "toughen" the cast bullet. This means it resists set back, sloughing or unwanted obturation during acceleration can be driven quite a bit faster, depending on the actual alloy, with accuracy than a standard lead/tin/antimony alloy. By using such excellent accuracy is obtainable as mentioned.

I've pondered that such bullets may give expansion similar to the all copper hunting bullets we see if one can drive them fast enough. The impact velocity level should not need to be as high as with the all copper bullet though. Remains to be seen and the use of a 4 part alloy (lead/tin/antimony/copper) is a pretty much an unchartered field with the use of such alloy in a hunting application(?).

I do know that with a soft malleable alloy my .30, .31, 8mm and .35s that are mildly HP to cause very good expansion are every bit as effective on deer as my .375 and .45 cal rifles using hard cast that do not expand. Yes, dead is dead but the expanding smaller caliber cast bullets kill quicker than non expanding ones and as quick as the larger calibers with non expanding bullets. Thus we find, over practical hunting ranges with cast bullets

There are many things we can do to enhance the accuracy of the bullet alone for higher velocity; we can wrap a copper jacket around it, we can wrap a paper jacket around the bullet and we can add copper to the alloy to "toughen" or strengthen the bullet. All of those methods then takes the cast bullet out of the category of the ternary (3 component) alloy of lead, tin and antimony of which alloy is the preponderance of the alloy used for cast bullets. Doing any of the above will raise the RPM threshold there by giving the potential for accuracy at a higher velocity/RPM. The RPM threshold of 120,000 - 140,000 RPM is for the common ternary alloy (lead/tin/antimony) most use with regular cast bullets. Let us not confuse that RPM threshold with the higher RPM threshold of other types of alloyed or PP’d cast bullets, especially those cast of a harder, tougher 4 part alloy.

Larry Gibson

[303Guy]

In using a blend of tin, babbitt, pure lead, and lino one can get a rather hard but still malleable alloy that is not brittle.

You don't want to add tin and copper Babbit. Copper Babbit is tin.

It wasn't me that melted copper gas checks. I dissolved the copper by first tinning it with rosin core solder then submerging it into the molten alloy. Copper will only dissolve in tin so it's best I think to make the copper-tin hardener separately. Be careful not to add too much copper to your alloy. While it strengthens/toughens the alloy and makes it malleable it also messes with the cast-ability of the alloy. Higher tin means higher copper but the copper needs to be no more than the eutectic at the freezing temperature. It's about 0.6% ?

The alloy I made had some crazy characteristics. For one I could measure the hardening over an hour. No quenching required although it did seem to gain about half an hour of natural hardening. Boolits fired into sand would turn completely inside out.



Pretty cool!

[badgeredd]

You don't want to add tin and copper Babbit. Copper Babbit is tin.

It wasn't me that melted copper gas checks. I dissolved the copper by first tinning it with rosin core solder then submerging it into the molten alloy. Copper will only dissolve in tin so it's best I think to make the copper-tin hardener separately. Be careful not to add too much copper to your alloy. While it strengthens/toughens the alloy and makes it malleable it also messes with the cast-ability of the alloy. Higher tin means higher copper but the copper needs to be no more than the eutectic at the freezing temperature. It's about 0.6% ?

The alloy I made had some crazy characteristics. For one I could measure the hardening over an hour. No quenching required although it did seem to gain about half an hour of natural hardening. Boolits fired into sand would turn completely inside out.



Pretty cool!

If you take a trip over to Rotometals and gander at their babbitt, you'll notice 4 alloys with fairly high copper contents. They would be #'s 1, 2, 3, and 11. If one alloys a bearing babbitt with pure lead and WW, and makes an attempt to balance the tin/antimony content, you'll be very surprised at just how hard you can make a boolit. You'll also find a great cast-ability to the alloy. If one water drops their castings, you'll get an immediate results in hardness that seems to hold for a good long time.

One attribute I have noticed is it is considerably harder to break the boolit. The alloy seems to be more malleable (for want of any better term). I suspect that a finer and more consistent grain structure results in part due to the copper. I am not a metallurgist or a chemist so that is pure guess on my part but the end results I have experienced seem to point in that direction. Perhaps we have a metallurgist or chemist on site that can share some insight into the mechanics of the alloy. I for one would love to know the precise reason the copper seems to improve the alloy.

Edd

[Larry Gibson]

badgeredd

I visited Rotometals and you got my attention

Using WWs at 95.5/.05/4 how do you "alloys a bearing babbitt with pure lead and WW, and makes an attempt to balance the tin/antimony content" percentage wise of each with which babbit?

Larry Gibson

[tonyjones]

There is an article titled "The Myth of Arsenic" by Wiljen at the lasc.us site. The article may also be found in Castpics. In this article Wiljen explains that arsenic does not serve as a catalyst in a lead alloy but, rather, serves as a grain refiner when heat treating and quenching cast bullets. Using certified alloys from a foundry for his testing he charts the results obtained using copper, selenium, sulphur and arsenic as grain refiners in a Pb/Sb/Sn alloy. The results are very informative and I encourage anyone interested to look up the article and read it.

I would be fascinated to know the implications of using two modifers, in this case arsenic and copper, in a Pb/Sb/Sn alloy.

I have read several posts here where members discussed their results from using COWW, Pb and a bit of babbit that contained copper. The results reported have certainly caught my attention. Has anyone performed detailed tests that would be willing to post their results?

Could this be part of the solution for those seeking accuracy at high velocity with a maleable bullet alloy and without leading?

Best regards,

Tony

[303Guy]

tonyjones, would you mind posting the link to that lasc.us article, please? I looked under the site but didn't see that one (I'm being lazy right now). I think when the word "catalyst" is used, "grain refiner" is what is being referred to.

'Malleable' would be the right term.

[tonyjones]

303Guy,

I've never figured out how to post a link here. However, if one were to scroll down to the bottom of this page and click on Cast Bullet Notes from lasc.us then click on Index to All Articles (upper right hand corner of the page) then scroll down to Additional Authors and Articles you will find it in the middle of the page right below the head.

Brackafrass! It probably would have been easier to learn how to post a link.

TJ

[303Guy]

Brackafrass! It probably would have been easier to learn how to post a link.

Not so easy.
I just learned a few days ago. I still don't know well enough to actually describe it.

Thanks. (By the way, your instructions are more than two steps long - that's not easy for me either!)

[tonyjones]

303Guy,

The term catalyst has implications, to me at least, that suggest a chemical reaction. In this case, grain refiners or modifers are terms that are metallurgical in nature. The only qualm I have with the article in question is the way the term catalyst is described. This is picking nits and is not intended as a criticism. The article is excellent. It opened my eyes and got me to thinking.

Regards,

Tony

[303Guy]

Thanks - I found it. Wow - I'm getting good!

I should get that little youngster in my avatar around. He's ten. He should be able to figure out all these things. (Flippin' youngsters!)

[badgeredd]

badgeredd

I visited Rotometals and you got my attention

Using WWs at 95.5/.05/4 how do you "alloys a bearing babbit with pure lead and WW, and makes an attempt to balance the tin/antimony content" percentage wise of each with which babbit?

Larry Gibson

Larry and others,

I am using Wiljen's Reloaders Reference which has an alloy calculator in it. The salvaged babbit I've been using is very close to the #2 babbit on Rotometals. What I have was analysed as having the same components and percentages. For ease I just ignored the copper when working up various percentage for alloys. I imagine I could get the percentages precise if I wanted to actually do the math, but I haven't up to now.

The alloy I have been using will be tweaked for more experimentation, but I can give you what I've been using to date. I use 5# COWW +4# pure lead +0.25# #2 babbit. The fairly close percentages come out to 94.8% Pb, 2.25% Sn, and 2.25% Sb with a trace of copper. I've used some other proportions to elevate the antimony and tin, trying to keep the tin and antimony balanced. I've used the alloy air cooled and water dropped...dependent on my intended velocity. Give it a try and let me know if it works for you.

Edd

PS To be honest, the idea of balancing the Sb and Sn is something I recall reading some place and it stuck. Where I read it and why it stuck, I have no idea. I suspect I came across it when I first started playing with my boolit alloy composition.

[jandbn]

For those with an interest, here is the link: The Myth of Arsenic

[onceabull]

That's a fine piece of work on alternatives to arsenic..But,nless trap shooting is going to outlawed worldwide, why do we need to worry about sources of arsenic.????? Onceabull

[357maximum]

I stepped into casting my own boolits with no knowledge of what I was doing whatsoever. I did not know all the preconcieved notions about cast. I was able to do alot of what some think is impossible. Being ignorant has it's advantages sometimes. I am not a math scholar or a chart lover. I simply TRY IT and change things till it works.

JUST DO IT...understand it later.


I use the babbit from the same source as BadgerEdd. It is a great "spice" when you need it. I add 5% of it to my 50ww/50pure and after waterdropping it allows me to do some pretty wicked and wild things and still expands enough to reliably kill deer sized critters in 35 caliber guns.


Using the 50/50+5%.....2600 plus with a 225grainer in the 35 whelen was not even a challenge....I did cheat and use a 14 twist barrel though.

The only limit to cast velocity with accuracy is YOU, the strength of brass/steel and the laws of physics and even them can be "bent" a bit. 2200 to 2400 in most standard sporting rifles is NOT difficult if: The boolit is appropriate and it fits, the alloy is correct, and you choose the appropriate burn rate of powder.

I have killed deer with my WD'ed 50/50 and 50/50+5% babbit and so far it has given me partition like performance and no failures with RNFP/WLNFP designs. It just works.


Have fun and good luck,
Michael