Cast bullet velocity limits?

[303Guy]

... I was adding 1% copper to ww's and 3% tin ...

Any idea what the WW alloy might have been? This is exactly the information I was looking for. No-one had really worked out the copper/tin/antimony content suitable for casting.

Thanks Larry, I'm with felix.

[nanuk]

303Guy
what is the best way to get the copper into the tin?

[nanuk]

i find it easier to change the twist rate rather than fight it.

My sentiments exactly. I've been "fighting" 10" twist for 40+ years.

The 12" twist is a lot better but you'll fall in love with the 14" twist..........especially in .30 cal.

Larry Gibson

Larry, what is the slowest twist rate you would suggest?

[Larry Gibson]

Larry, what is the slowest twist rate you would suggest?

You have to consider 3 things; 1st is the twist rate to give the selected cast bullet proper stabilization. There are 3 basic classes of bullet stabilization; minimal, adequate and over stabilization. You'll want the bullet to be between minimal and adequate stabilization at the prjected velocity you want to attain.

Second consideration is the RPM at the projected velocity should not exceed 140,000 RPM, preferably 135,000 RPM to give a fudge factor.

The third consideration is case capacity. The cartridge should be able to achieve the projected velocity with a slower burning powder (slow medium to the low end of the slow burners with consistent ignition. Example; the '06 will push to 2700+ fps with a slower burning powder at less psi than the .308W because the case capacity of the '06 allows the use of a slower burning powder.

With the use of a ternary alloy of lead/antimony/tin in a properly designed cast bullet for high velocity;

In .30 cal a 14" twist barrel 26"+ long is about optimum for 2600 - 2650 fps with the .308W. Loading density is at max capacity with 4350/RL19/H4831SC and the RPM threshold falls within that velocity range. More velocity can not be had without using a faster burning powder which raises the psi and gives faster accelleration which then actually lowers the RPM threshold with a loss of accuracy at a lower velocity.

It is my contention that the 311466 or the LBT 150 gr bullets cast of the mentioned ternary alloy can be driven to perhaps as high as 3000 fps with very good accuracy using the 30-06 cartridge in a 28 - 30" barrel with a 16" twist. In the near future I will be ordering such a barrel to find out if my contention is correct. A cartridge with the case capacity of the .308 Norma Magnum would probably be better IF it had the longer neck of the '06 case. As is, all standard magnum .30 cals have necks that are too short to give the cast bullet the full support it really needs for such high velocity levels. The idea is to have the bullet seated in the neck properly and have a tight necked chamber for minimal case neck expansion.

I've also thought that a 16" twist 26"+ barrel chambered for the 22-250 with the shoulder bumped back so the 225462 Lovern bullet would fit into the neck would be an excellent .22 CF cast bullet high velocity cartridge. I would have the scraper groove removed from my mould for that bullet design.

Many years ago a friend had 250 Savage that had been rechambered to .257 Roberts. We were able to get excellent accuracy at with the 257464 at 2550 fps (yes I had an Oehler chronograph back in '75) with old 4831. I didn't really understand the why of getting the accuracy we did at that high of a velocity back then but realize now the rifle had a 14" twist and the cartridge case had a neck length that supported that Lovern style bullet without the GC being below the base of the case neck. It also had a tight chamber neck with made for minimal neck expansion. Thus all the ingrediants were there for successful high velocity accuracy with cast bullets.

Larry Gibson

[303Guy]

nanuk
I did it by tinning the piece of copper sheet then submerging it in the melt. I'd say it's best to add it directly to the tin source before adding the tin.

It dissolves slowly into lead with tin in it. My particular alloy went weird on me so I'm thinking I didn't have enough tin in it. My latest alloy had a chunk of Babbit in it which is around 6.5% copper, 6.5% antimony and around 85% tin. I haven't worked out the percentages yet but if the melt and the molds are hot enough it casts beautifully. It does seem to cast close to mold size.

[felix]

Copper and arsenic form complexes that might have to be controlled independently of one another. Just how, I have no idea on what total mixes do what and when, except that copper demands very consistent stirring a well fluxed pot throughout the casting session. Copper cools very dramatically in the mixes I have used and will be in different locals on each boolit if temps are not well controlled. I would suggest a PID hotplate for the mold before a pour, as well as for the pot. I do know for sure that a coppered boolit will compete well with a PP boolit provided each boolit can be made the same. Copper is an amazing ingredient to our junk alloys and should be used with extreme care to make groups stand out. PPing might be easier with less frustration in the long run for this reason. You can boost most velocities by at least 200 fps without trying too hard using copper for smallish diameter boolits. ... felix

[famdoc2892]

Gentlemen, it's no stretch to say you've blown my mind with your discussion in this thread, and I thank you! Just goes to show how forums can be invaluable in passing along knowledge as I "drink from the fire hose!"

[badgeredd]

Copper and arsenic form complexes that might have to be controlled independently of one another. Just how, I have no idea on what total mixes do what and when, except that copper demands very consistent stirring a well fluxed pot throughout the casting session. Copper cools very dramatically in the mixes I have used and will be in different locals on each boolit if temps are not well controlled. I would suggest a PID hotplate for the mold before a pour, as well as for the pot. I do know for sure that a coppered boolit will compete well with a PP boolit provided each boolit can be made the same. Copper is an amazing ingredient to our junk alloys and should be used with extreme care to make groups stand out. PPing might be easier with less frustration in the long run for this reason. You can boost most velocities by at least 200 fps without trying too hard using copper for smallish diameter boolits. ... felix

Felix,

You been around this cast boolit thing a lot longer than I have so take my following comment FWIW.

I have been messing with the babbit as a source of copper and tin in my alloys. I believe you are spot on the amount of copper that can be successfully alloyed into boolit material. What I am finding to date is the 1% may be a bit on the high side. Also I suspect that the amount of tin in the alloy also affects ones results. There seems to be a correlation between tin and copper content in my experience. After working out a couple mixes, I worked up a spread sheet to figure alloys to include specific copper content using know base metals. One I have been using has 0.4% copper. I have worked up another that will have about 0.6% copper. All of the alloys I have worked up (theoretical and practical) I have tried to balance the tin/antimony content to within 0.05%. Now I have to find a way to incorporate the arsenic content also. My problem has been a way to KNOW what the arsenic content is of a base metal like magnum shot. Once I figure that out I should have a fairly precise alloy calculator figured out.

Edd

[badgeredd]

I had a thought last night about the adding of copper to an alloy and wanted to get some thoughts on the feasibility of it.

This idea goes back a couple years when I got some telephone cable chunks. The cable had sat in a barn for several years before I got it. When I stripped the lead sheathing off of the wire, it was coated inside with copper oxide. I melted down the sheathing and it seemed to be quite hard. It occurred to me that perhaps a fellow could add chemical copper oxide to ones melt to add in copper. What do you chemist types think...is it feasible?

Edd

[popper]

Don't try copper sulfate. Telephone cable sheathing has lots of special stuff in it. Has to be corrosion resistant and strong. Google it and battery grid materials to see what they have to do.

[geargnasher]

Don't try copper sulfate.

That was my first thought! I mean, to try it. I would think it would decompose in hot lead and maybe react to form PbSo2-3 and elemental copper, but I don't know much about relative reactivity and if heat alone would be a sufficient catalyst.

I bet it would stink!

Gear

[runfiverun]

i have been giving copper sulphate some serious thought recently.
to get the elemental copper.
the sulpher is an excellent grain refiner.
i don't know chemistry but i know what works in alloy.
so what am i missing?
you can add both to an alloy
so how is the copper sulphate different than just copper and sulpher?

[geargnasher]

What we're missing here is someone with a serious background in inorganic chemistry. Where's Caleb when you need him? I'm thinking the stuff might could be added to fully melted alloy rather than folded into a carefully maintained "mush" like with straight sulfur.

Maybe I'll try "Ask.com", "What happens when you add copper sulfate to molten wheel weights?" Ha! that should be good for a laugh.

Gear

[runfiverun]

glen fryxell might could answer the question too, he has the back ground.

[whisler]

From wikipedia: At 650 °C, copper(II) sulfate decomposes into copper(II) oxide (CuO) and sulfur trioxide (SO3). Note the C!!!

[popper]

Nasty - toxic gasses!!!! Plus sulfuric acid. I checked into it, but if you find a successful method, I'm interested. I think PbS03 is a hard but flaky salt you can of course get electrically.

[badgeredd]

Telephone cable sheathing has lots of special stuff in it. Has to be corrosion resistant and strong. Google it Didn't find a thing on cable sheathing. and battery grid materials not in the same class to my knowledge to see what they have to do.

How about pointing to a place to back up that warning. This is the first I've heard about toxins (beyond lead) contained is phone cable sheathing which is lead alloyed with antimony and tin for strength and corrosion resistance.

The green deposits I found inside the cable and some of which deposited on the lead alloy sheathing was copper oxide...copper rust for want of a better terminology. I am wondering if our normal wood sawdust or wood stir sticks might possibly be a catalyst to help break the bond between the oxygen and copper atoms. I was hoping that perhaps we have a person among us that has a solid back-round in chemistry and possibly some suggestions.

Edd

[runfiverun]

SO2 is sulpher dioxide or sulpheric acid which can be neutralized with K-31 or soda ash.
sulpher trioxide is different.

if that's truly 650 centigrade i think i can easily stay under that.

y'all know this stuff is used to remove tree roots from sewer lines,
is soluble in water, and can be used to copper plate lead boolits with an electrical charge.

there's other way's to get what i want done, just looking for a simpler repeatable method.

[badgeredd]

there's other way's to get what i want done, just looking for a simpler repeatable method.

RFR, I couldn't have said it better. In my mind, there has to be a rather simple way to add a know amount of copper to our boolit alloy. That is why I started experimenting with the tin based babbit in the first place. AND I have figured out a alloy calculator to give me the amount of copper that is present in my alloys using know babbit mixes...but babbit is rather expensive so my quest goes on for a simpler way to add copper that isn't labor intensive.

Edd

[mauser1959]

I realize that this is an old thread , but I have a question for you guys that shoot a lot more high powered rifles then I . I was recently given a Remington 721 in 270w . All the information that I have found seems to point to the fact that this rifle probably has a 1 in 10 twist . What would be the accuracy point for the gun be ; just an educated guess ? Also what would be the preferred weight of the best bullet ? Would the difference in cast versus ; jacketed bullets make a way the bullet would stabilize . I am wishing to go to a 150 grain bullet , whether gc cast or jacketed . I really need input on what is going on . I hate to admit this , but I normally just shoot pistol bullets that I cast .