How significant is bullet diameter change when lead:tin mix proportion changes?

[Naphtali]

I want to cast .72-caliber concials. How significant will be bullet diameter as cast change between conicals when casting mixes are 20:1 and 10:1? I ask because do not size after casting and I am unable to control what mix I use for each projectile from my single pot.

[Jeff Murray]

You might want to weigh some of your bullets to see if there is a difference in weight based on different metal mixes.  A difference in weight could affect elevation-based point of impact

[Daryl]

I'll take a stab at that. The 10:1 bullet might be upwards of .001" larger - maybe not.
Seems to me, the largest changes in diameter with purity, come from pure lead to antimony %age.
The difference between 10:1 and 20:1 is not great I suspect, as to diameter.
IMHO, 10:1 is mostly usable in smokeless loads.
Easiest way is to cast some and try it.  10:1 can always be changed to 20:1 and visa-vis.

[Birddog6]

I think weight & dia will make a dif.  Most of the time, change of anything in a load will change the POI.

If you use lead with a alloy in it, it will usually come out of the mold smaller in dia & weigh less than a pure lead ball. That will definitely change the POI because you will have less velocity.

[smylee grouch]

I think weight & dia will make a dif.  Most of the time, change of anything in a load will change the POI.

If you use lead with a alloy in it, it will usually come out of the mold smaller in dia & weigh less than a pure lead ball. That will definitely change the POI because you will have less velocity.

              When I mix wheel weights or tin in with the lead it always seems to be tighter loading using the same patch/lube as I use with pure lead out of the same mold.

[Daryl]

Keith, you mean the opposite, I think. Alloys cause the ball to be larger as well as lighter.
Lighter as any alloy is lighter than the lead it is replacing in the melt. Antimony is even lighter than tin and causes
more weight loss, but larger diameter yet.
The alloys are harder loading, as the balls are harder and more resistant to compression which is necessary in tight fitting loads many of us use.
I was still able to load WW balls (466gr.) from my .682" mould, with the .030" 12 ounce patches I used back in the 890's. It was not easy getting
them started and you (me) had to really WANT them to start.  It took an effort on the starter to get them into the bore. Now, when using hard lead
I use my .662" (16bore) mould, which loads quite nicely with hard balls & the .014 ounce denim, and still gets to the bottom of the grooves with some
compression.

[Tim Ault]

If it’s just a binary alloy of lead/tin it won’t be that much growth in dia  possibly .0005 -001” now if you add antimony to that mix you’ll get larger growth .   The slight amount of tin in the alloy does help with fill out in the mould so some growth in dia  maybe because of this too

[Dphariss]

I would consult Lyman’s Cast Bullet Handbook for reliable information.
1:10 alloy is not necessary. Once past a certain level of tin the hardness does not increase a great deal or so I have read. I do know that 1:20 is  too hard for a hunting bullet at least in 40 caliber. The old 1870s-90s sleek LR bullets for BPCR were about 1:14 the blunter hunting bullets of the same or similar weight were softer, sometimes pure lead depending on the loading. The Gov’t bullets for 45-70 1:16 as were some bullets for repeaters.
I believe that it was Brockway in Ned Roberts book who told of trying to swage some 1:20 or harder alloy for a shooter and actually burst his swage. I would not go harder than 1:20 don’t think there is a valid reason. Even 1:40 will lower the melt temp and make the metal flow in the mould a lot better. It should not make a great deal of difference in diameter. Adding other metals to the mix like antimony will make the bullets much harder and will increase the diameter.. 

Also note that while hard lead can be useful in MLs it must be noted that some steel targets can suffer serious damage by even slightly harder RBs unless the targets are AR400 or AR500 alloy. With slightly harder balls my 50 cal will cut 3/8 chain links at 25 yards or so and will dimple some factory pistol targets with pure lead at 40-50 yards.
Given the power of the 72 cal RB and the dismal history of conicals as related by Forsythe and Baker I don’t see a need for them.

[Maven]

I would consult "Lyman’s Cast Bullet Handbook, 3rd Edition" for reliable information....Dphariss

Exactly!

[Daryl]

Given the power of the 72 cal RB and the dismal history of conicals as related by Forsythe and Baker I don’t see a need for them.

The reason hardened lead did not "catch on" in muzzleloaders over spherical projectiles, is due to the lack of accuracy of a hardened bullet in rifles when loaded from the muzzle.
If small enough to load, they will not obturate to 'take" the rifling. Back in the 70's, there were guys trying to use WW for 58 Minnies, and getting dismal accuracy with them, due
to the hardened Minnies failing to obturate into the rifling. They also fouled the bores badly due to their poor fit.
Round balls, especially hardened round balls, with the addition of mercury or tin, increased the penetration on dangerous game with round balls, to greatly exceed the penetration
of the necessarily soft conicals. (Mercury was used in the 19th century to harden lead.) How effective Mercury was as a hardening agent, I do not know, nor have any desire to test.

[yulzari]

Given the power of the 72 cal RB and the dismal history of conicals as related by Forsythe and Baker I don’t see a need for them.

The reason hardened lead did not "catch on" in muzzleloaders over spherical projectiles, is due to the lack of accuracy of a hardened bullet in rifles when loaded from the muzzle.
If small enough to load, they will not obturate to 'take" the rifling. Back in the 70's, there were guys trying to use WW for 58 Minnies, and getting dismal accuracy with them, due
to the hardened Minnies failing to obturate into the rifling. They also fouled the bores badly due to their poor fit.
Round balls, especially hardened round balls, with the addition of mercury or tin, increased the penetration on dangerous game with round balls, to greatly exceed the penetration
of the necessarily soft conicals. (Mercury was used in the 19th century to harden lead.) How effective Mercury was as a hardening agent, I do not know, nor have any desire to test.

An additional factor was the necessarily larger mass of the conical versus the spherical ball which limits the powder charge due to the resultant recoil of a larger mass bullet for a given load. This was important to the likes of Forsyth and Baker who wanted a flat as possible trajectory but for a limited range. The spherical ball gave a good balance and the penetration could be controlled by the hardness of the alloy. One can see this in period real life with the Royal Navy altered pattern 1842 musket which had a reduced charge from the smooth bore spherical ball to that used with the conical once they were rifled out from 0,753” to 0,758”.

FWIW the 0,58” bore 1:78 twist of the rifle musket falls within Forsythe’s limits for the bore (albeit with wide lands not his narrow ones) and, at short ranges, I got better accuracy with a patched round ball from a Parker Hale Enfield than any conical. Once past maybe 120 metres that altered to the advantage of the conical.

[Pukka Bundook]

Yulzari/John,

Good to see you here! I was beginning to worry about you. Not 'seen ' much of you on the other channel for a long time!
So pleased to see you posting, and hope Su is well!!

[Hungry Horse]

 I’ve found that along with the size increase when casting bullets from alloyed lead, it also tends to make the lead more brittle. In my .58 I found the skirts on the minis got so brittle that part of them occasionally would break off sending the bullet off target.

Hungry Horse

[yulzari]

Yulzari/John,

Good to see you here! I was beginning to worry about you. Not 'seen ' much of you on the other channel for a long time!
So pleased to see you posting, and hope Su is well!!

PM sent.