bullet casting.

[Randy Bohannon]

Tin/Lead alloys do age soften, they stablise after a while but that does not mean they do not age soften from just cast.

Lead-tin (Pb-Sn). Which metals do we add to lead to make better bullet metal and why? The first and most obvious need here is to make the alloy harder, but there are other factors that play into this answer as well. Historically, tin was used because it was readily available in pure form, mixed easily with molten lead and contributed desirable properties to both the molten and solidified alloy (castability and hardness, respectively). Tin also increases the hardness of the alloy but does not interfere with the malleability of lead (a key point that we‘ll return to). Tin lowers the viscosity and surface tension of the molten alloy, allowing it to fill out the mould more effectively, resulting in a higher quality bullet. Tin is limited in its ability to harden lead, achieving a maximum hardness of about 16 BHN at 40% tin.

These binary lead-tin alloys undergo slight to moderate age softening upon storage (1-2 BHN units), with the harder alloys undergoing more of a change than the softer alloys. The hardness of a binary lead-tin alloy generally stabilizes after about 2-3 weeks.

Heat treating binary lead-tin alloys does not provide any change in hardness. At typical lead pot temperatures, lead and tin are infinitely miscible with one another, at the eutectic temperature (361 F) tin is still soluble to the tune of 19%, but at room temperature tin is still soluble in lead at the 2% level, meaning that as the bullet cools down there is significant precipitation of a tin-rich solid solution in the form of granules and needles in a matrix of lead-rich solid solution.

[thibben]

RB,

Concur, which is why I said 'lead tin alloys do not to any degree change over time' as not many folks cast bullets and shoot them the next day (well I don't) and if you look at the link I posted you will see Dan T's results for the alloys I listed, 20 & 16:1, after 2 or 3 days 'that's it' they do not change.

I have found this to be accurate by measuring the harness of both bullets before loading , which could be months after casting, and pre mixed ingots , which could be many months after smelting (I premix quite a few kg using commercially pure lead and tin). FYI I use the Cabin Tree tester (see here: http://www.texas-mac.com/Evaluations...s_Testers.html ) which is now made by this bunch: http://cowboybullets.com/Lead-Tester_p_57.html

Brgds

Terry

[Randy Bohannon]

RB,

Concur, which is why I said 'lead tin alloys do not to any degree change over time' as not many folks cast bullets and shoot them the next day (well I don't) and if you look at the link I posted you will see Dan T's results for the alloys I listed, 20 & 16:1, after 2 or 3 days 'that's it' they do not change.

I have found this to be accurate by measuring the harness of both bullets before loading , which could be months after casting, and pre mixed ingots , which could be many months after smelting (I premix quite a few kg using commercially pure lead and tin). FYI I use the Cabin Tree tester (see here: http://www.texas-mac.com/Evaluations...s_Testers.html ) which is now made by this bunch: http://cowboybullets.com/Lead-Tester_p_57.html

Brgds

Terry

Very interesting, thank you.

I like that Cabin tree tester very much, particularly as it seems to be able to measure run out as well...

[thibben]

RB,

Bit off topic but what do you 'shoot'? I'm assuming BPCR as ML and gallery do not require that much 'fineness' (no slur intended, just an observation!)

T

[Randy Bohannon]

I have obtained a Milhec copy of a H&G 30 cal mould that produces something called the "Ness Glanceproof (or) Safety" bullet: http://castboolits.gunloads.com/show...e-proof-boolit

It has a hollowpoint which is almost .200 wide at the mouth and as deep as the bottom lube groove and is designed to come apart completely, minimising the chance of significant pass through and ricochet.
The hollow portion is the part which is getting squashed by the nose punch of the luberisizer and hence my need for a stronger alloy.

I suspect antimony might be the way forward to promote fragmentation.

[tacfoley]

RB,

Bit off topic but what do you 'shoot'? I'm assuming BPCR as ML and gallery do not require that much 'fineness' (no slur intended, just an observation!)

T

BPCR is shot out to 1200 yards.

Muzzle loading matches are also out to 1200 yards.

I weigh my bullets to within 2gr, even though they weigh either 405gr or 535gr. I try and make them them very best I can within my limitations.

I don't shoot gallery, so I can't comment on it.

tac

[thibben]

BPCR is shot out to 1200 yards.

Muzzle loading matches are also out to 1200 yards.

I weigh my bullets to within 2gr, even though they weigh either 405gr or 535gr. I try and make them them very best I can within my limitations.

I don't shoot gallery, so I can't comment on it.

tac

Tac,

Thank you for input, aware of the different comps, was just after RB,s particular application to possibly comment.

Have only shot competitively to 1000 yards myself with BPCR. ML is too much faffing personally, I’ll do my loading at home

Re bullet weight, using a good PID controller on the pot and a preload mold handle my bullets drop +/- 1g but I sort them into 1/2g groups. Get the odd one that’s too far +/- but they are few and used for foulers

Brgds T

[Randy Bohannon]

Tac,

Thank you for input, aware of the different comps, was just after RB,s particular application to possibly comment.

Have only shot competitively to 1000 yards myself with BPCR. ML is too much faffing personally, I’ll do my loading at home

Re bullet weight, using a Good controller on the pot and a preload mold handle my bullets drop +/- 1g but I sort them into 1/2g groups. Get the odd one that’s too far +/- but they are Fee and used for foulers

Brgds T

Tac shoots BPCR out to 1200 yards

He also shoots Muzzle loading matches are also out to 1200 yards.


He weighs his bullets to within 2gr, even though they weigh either 405gr or 535gr. he tries and makes them them very best he can within his limitations.


He doesn't shoot gallery, so he can't comment on it.

Which is something at least.