Question on Cast Hardness

[TXBRILL]

I am getting ready to cast some Hollow Base 405 grain boolits for an old trap door. When I research suggested alloy everyone seems to agree that somewhere between 20:1 to 30:1 lead to tin is recommended for a BHN of around 9. My question is if my WW's test around 9 will it have the same properties as the lead tin mix. I assume the WW's have a different alloy than tin.

[btroj]

Not really. Close, but not the same.

Cut the wheel weights 50/50 with pure, maybe add 1 percent tin for fillout, and air cool.

[Larry Gibson]

BHN does not measure malleability. The lead/tin will obturate easier than the ternary alloy with antimony in it. BTW; The Lee 405 HB, if that's the one you are using, is a direct copy of the M1873 bullet. The "HB" is not really that, it is a dish cavity to maintain the given weight while maintain the same external dimensions. The "HB" is not there to aid the bullet to expand and take the rifling ala a minie' HB'd bullet. That comes from the manuals for the M1873 and later TDs BTW (photo of 1st manual for the M1873). Also the original M1873 405 gr bullet was made of 12-1 alloy.

Larry Gibson

90257

[NYBushBro]

BHN does not measure malleability. The lead/tin will obturate easier than the ternary alloy with antimony in it. BTW; The Lee 405 HB, if that's the one you are using, is a direct copy of the M1873 bullet. The "HB" is not really that, it is a dish cavity to maintain the given weight while maintain the same external dimensions. The "HB" is not there to aid the bullet to expand and take the rifling ala a minie' HB'd bullet. That comes from the manuals for the M1873 and later TDs BTW (photo of 1st manual for the M1873). Also the original M1873 405 gr bullet was made of 12-1 alloy.

Larry Gibson

90257

So, the 12:1 alloy might also be suitable for loading .43 Spanish Remington? I always wondered what a suitable mix might be for it. I plan on using AA-5744 (but not hot-rodding it.)

[Larry Gibson]

If you are sizing to .459 and depending on "bumping up" obturation in the original TD barrel then I suggest the softer 20-1 alloy or even 30-1 with the 405HB. However if you are shooting at groove or groove+ sizing then the harder 20-1 works very well. Frankford Arsenal did considerable testing of alloys for the 500 gr M1882 bullet and settled on 16-1 alloy which is what I use for my 460500 Rapine Gvm't bullet. I use 30-1 alloyed bullets for Carbine 45-55 loads and 20-1 for the service level 1873 45-70 loads with BP. I size my 405HBs and 500 gr bullets at .4615 for my TD and do not depend on bumping up as did the original loads.

Larry Gibson

[TXBRILL]

Thanks for the info. Yes it is the Lee Mold. I was planning to load them un-sized. I have not started to experiment yet, I am really just trying to figure out the best way to start. My plan now is to cast 20 or so 25:1 and load with 55 gr. of FFG. In the past I have used 5744 with commercial hard cast but was not happy with the results.

[Larry Gibson]

Try 25 gr 5744 with a 1 gr Dacron filler under them.

Larry Gibson

[waco]

Try 25 gr 5744 with a 1 gr Dacron filler under them.

Larry Gibson

I see this powder come up A LOT when cast boolits are the topic. Larry, can you give me your thoughts on this?

What is its burn rate? Somewhere in the 4227 range? A bulky powder maybe that fills the case nicely?
Waco

[62chevy]

I see this powder come up A LOT when cast boolits are the topic. Larry, can you give me your thoughts on this?

What is its burn rate? Somewhere in the 4227 range? A bulky powder maybe that fills the case nicely?
Waco

Hodgdon list it as #67 on their burn rate chart just below IMR 2427 #64.

http://www.lasc.us/BurnRatePrint.htm

But that is the best I can tell you about it hope this helps.

[Larry Gibson]

I see this powder come up A LOT when cast boolits are the topic. Larry, can you give me your thoughts on this?

What is its burn rate? Somewhere in the 4227 range? A bulky powder maybe that fills the case nicely?
Waco

Yes it's burn rate is right about the same as either of the 4227s. Like them 5744 doesn't burn efficiently and low end pressures (for this "slow" burning 'fast" burning powder). Thus with lighter weight cast bullets in many cartridges the velocity will be too high for best accuracy before the psi is sufficient for efficient burn. The Dacron filler helps in many cases as in this one using 400 gr or light cast in the 45-70. The Dacron filler is not needed with heavier cast bullets. While "bulkier" than the 4227s it still remains a low density load for most cases. Just make sure the Dacron filler is a filler and not a wad.

Larry Gibson

[waco]

Interesting. I'll look into trying some if I ever run across any. Can't find squat in these parts right now....
Thanks for the answers guys.

[MtGun44]

I have heard this claim that the Lee 405 HB does not act like a Minie bullet and
expand at the rear due to pressure. My experience with a very large groove diam
TD was that with 30:1 I got great accy where everything solid base was into 2 feet at
100 yds. and usually sideways too. I did not have a solid base larger than .459
and the HB was at about that diam, I forget exactly, unsized.

I assumed that this is due to Minie expansion, but can't prove it. What other
mechanism would explain the massive improvement? I was using Unique and
the Lee solid base did not work at all, although it was wwt alloy. I suppose I
need to cast some solid base out of 30:1 and see how they do. I tend to doubt
that bump up could do this, but perhaps that is possible.

The HB gave a 4 inch group first try and similar on subsequent tests. I was
expecting Minie type base expansion, so assumed that I got it.

Bill

[Larry Gibson]

MtGun44

The claim is not that it will not work as the minie' because under some circumstances it will to a very limited degree. The truth is that the "dish" was not designed and put there for expansion but simply to retain the specified weight at the specified external dimensions of the bullet. It is not a "claim" but simple fact as it is so stated on all the platte drawings in all the manuals from the one I pictured to the latest ones 25+ years later. It is so stated in the arsenal (Frankford if I recall correctly) papers regarding the development of the 500 gr bullet. A simple reading of any of those manuals will show that. Do you want me to copy and paste?

Also any bullet will expand and set back if the alloy is soft enough as with a 30-1 alloy. However, the original M1873 bullets were of 12-1 alloy which is considerably harder. The original idea (borne out and substantiated in the reports on the development of the 500 gr M1882 bullet) for the use of .459 sized bullets in the larger groove diameter barrels was on firing the bullets would obturate (bump up) to "take the rifling". The TD barrel specs were for a .450" bore with 3 lands and grooves of equal width with grooves being .005" deep. The "bumping up" was a common belief for use with BP cartridges back then. Even the 500 gr bullet was sized at .459" and dependent on "bumping up. During actual use it was found the 405 gr bullets rarely "bumped up" adequately for best accuracy even with the full 70 gr BP service load. "Bumping up" was none existent with the 45-55 carbine loads. The 405 gr bullet did not have the inertia and was too hard with the 12-1 alloy used. Thus the 500 gr bullet was developed as it had the inertia to "bump up" and the alloy was changed to a softer 16-1. That 16-1 alloy also helped the accuracy of the 45-55 load a bit.

Thus we see the purpose of the dish (what we commonly call the "hollow base" in the Lee bullet and the original 405 and 500 gr bullets) in the base of the bullets was simply to retain the dimensions and weight of the bullets as specified. The fact that anyone may or may not get minie' style expansion of the hollow base on a much softer cast Lee 405 gr bullet, especially with fast burning smokeless powders such as Unique, is not relevant to the reason for the dish in the base of the bullets.

I've shot enough of the Lee 405s cast of 20-1 and 16-1 alloys in my own original TD with BP and smokeless powders to know that bumping up is not consistent nor beneficial to best accuracy just exactly as the arsenals found. I do not size either the Lee 405HB or the Rapine 46050 (duplicate of the M82 bullet) at .459 and expect obturation. I size them at .4615 to fit the barrel to begin with. With such I get 1.5 - 2 moa groups at 200 yards out of my target TD with BP or smokeless powder.

The OPs question is whether his WW alloy with a BHN of around 9 would have the same "properties" as a 20-1 or 30-1 alloy. The answer is "no" as the expansion properties are different. The WW alloy's antimony changes the malleability. And, the "hollow base" of the M1873 bullet (the Lee is a duplicate) is not there to aid in expansion, obturation or bumping up. The use of the softer and more malleable 30-1 alloy has the "properties" to obturate with a correct and safe powder charge for a TD. Those "properties" are independent of the HB on the Lee bullet. A flat based 457124 will obturate just as much as the Lee 405HB when of equal weight and alloy. Has to do with inertia of the bullet and malleability of the alloy not the HP of the Lee 405HB bullet. I've shot enough of each to know.

Spence Wolf told me he also had to go to a 20-1 alloy with his replicant 45-70 service loads (in his excellent book) using the Lee 405HB bullet to get any reliable obturation with 70 gr BP. Spence is the one who designed and had Lee make that bullet BTW. Reading the manual; "A Course of Instruction in Rifle Firing by Col. T. T. S. Laidley, Ordnance Department, U.S. Army 1879 (the first actual marksmanship manual published by and for the Army) shows the use of the 20-1 alloy for the M1873 bullet was giving superior accuracy to the 12-1 alloyed arsenal bullet, especially at long range. There is no mention in any manual of the dish being used for nor giving any minie' style expansion.

I recommend, for 45-55 TD carbine loads, the 405HB, the Lyman 457124 or similar M1873 style bullets be cast of 30-1 or even 40-1 alloy and used "as cast" if they drop at .460 - .465. That is with BP, duplex or smokeless loads duplicating the 1100 fps of the original 45-55 carbine load. Accuracy will be far better than sizing the bullets at .459 and then depending on obturation or "bumping up" of the bullet to "take the rifling".

BTW; the concept of the groove diameters being a bit larger than the bullets and depending on "bumping up" was held clear up through the U.S. 30 cal M1892 rifle. It was only about half way through the 30-40s short use that it was found the rifles were a lot more accurate (and the barrel life longer) if the bullet was of equal diameter or even .0005 larger than the barrel groove diameter. That information can be found in Whelen and Hatcher's early writings. Thus we now know that using bullets that "fit" the barrels of TDs will be much more accurate than those which are undersize and dependent on "bumping up". Just a foot note is all.

Larry Gibson

[TXBRILL]

Thanks to all for spending so much time and energy to educate me. I feel pretty smart that I was planning to start where Larry suggests, I will go 30:1 and let all y'all know how I make out.

Thanks
Allen