What BHN do you guys consider optimal for the 10MM at about 1200fps with no gas checks?
Barrel fit is key, I know, but what is "Key" as far as hardness goes.?
I have an Alloy calculator in Excel. I have clip on WW, I have Mono type and I have pure lead pipe. With the calculator and these components I can mix up pretty much what ever I need or want as far as BHN goes, yes?
So, what BHN do you guy shoot for in you 10MM bullets?
For most of my 10mm and others, I shoot a straight wheel weight hardness, air cooled sized to 0.4015", lubed now with White Label Lube's Carnauba Red. http://www.lsstuff.com/ (http://www.lsstuff.com/)
This one requires some heat to apply and is a little softer but stays put. This lube is reasonably priced including shipping.
But I use to use the Rooster Labs Zambini Red, but the guy that was producing their lube quit making it. (It was a harder lube and required some heat to apply.
It helps to have them sized and lubed ahead of time to allow the alloy to age harden after the sizing process. 8)
If you get too hard a BHN hardness the bullet will not undergo obturation to take to the bore.
I have run 200 grain bullets at both 23-24 bhn and 12-14 bhn. Same alloy, only difference was whether I water dropped them from the mold.
I lube with Felix lube + a blue crayon, and have no issues with leading with either one.
The hard bullets have been tested with a 205 grain flat nose in milk jugs. Based on the exit hole diameter of the eleventh (yes 11th) jug, the bullet did not expand at all.
I have not repeated the test with the air cooled bullets.
Your WW alloy should be fine. I don't know how much monotype or pure you have. Generally folks have plenty of ww and hoard the rest. If you are in a unique situation and would rather use your other alloys, I would mix 50/50 mono to pure and air-cool them.
QuoteI would mix 50/50 mono to pure and air-cool them.
According to my alloy calculator a 50 pure lead and 50 Monotype = Tin 4.5%, Antimony 9.5%, lead 86%, with a BHN of 18.6.
Just a starting point. I have always wished my air-cooled were just a bit harder. Not that I have issues like leading...Just seemed like 16-18 would be more ideal for terminal velocities of 1100-1200 fps.
4:1 should get you closer to old WW alloy and a BHN of 12-13, and should be about identical to the isotope alloy I cast.
Practice loads = BHN 12-14, standard wheel weights, 200 gr at 1000 fps with Carnuba Red lube mixed 50-50 with some blue stuff (old Magna lube) I want to use up.
Hunting loads or backup for hogs = BHN 21+ (water dropped wheel weights), same lube.
Sean
Quote from: The_Shadow on June 11 2013 08:25:05 AM MDT
If you get too hard a BHN hardness the bullet will not undergo obturation to take to the bore.
Shadow, if the bullet is already sized larger than the bore, it doesn't need to be soft to fit. IME, the requirement for soft bullets to seal the bore applies more to revolvers with mismatched barrel/cylinder dimensions, and black powder guns. Not so much for modern semi-autos with properly fit bullets.
In my experience with 10mm plain base bullets at real 10mm power levels, harder is better. I have not yet found a point where a cast bullet can be too hard for the 10mm, unless you want expansion. When I recover my bullets, the harder bullets show less gas cutting of the base, and generally give better accuracy and less leading. I normally use heat treated wheel weights. (heat treated, because it's more consistent than water dropped)
Yondering, I can understand that and I know you've done the slugging of the bore's on yours also. Here lately I have been loading the Cast HP from the Lyman Devastator Molds and for the 10mm and 40S&W I have been shooting a lot of these so the slightly softer wheel weight alloy has been fine in several of my guns.
(https://s20.postimg.org/w8zzes7nx/5203a340-3857-45ba-8509-a1afaf90a7a3_zpsc77a1075.jpg)
In fact I sent some to be gel tested by Raggedyman when he gets some time to test them to see how they do...Water is hard on them at 10mm velocities if driven beyond 1250 fps and 40S&W at 1125 was better. Intercooler has been keeping him busy. 8) So I'm still waiting to see his results.
Although I shot some 357 mag 165 Kieth style plain base (non-gas checked) @ 1225 fps thru 4 jugs stopped in the 5th that showed no cutting and deformation.
But I do agree about the oven heat treatment.
Yeah, figuring out the correct alloy for hollow point use is a whole other subject, and more complicated too. The size and shape of the hollow point introduce a couple more variables, so you really have to figure out a solution for a specific load. The challenge I've found with 10mm cast hollow points is balancing strength & hardness of the alloy with ductility, for good expansion without fracturing, or over expansion and shedding weight. It's real easy to make a 10mm hollow point load that leaves nothing but part of the rear driving band, and a lot of little fragments.
Those Devastators are interesting bullets, and expand easily with WW alloy at moderate velocity. I think a shallower hollow point is needed for full power loads though, if you want the bullet to stay together (not necessarily a requirement, it's fun when they blow up too.) Have you seen the shallow cone hollow point in the 180 & 200gr bullets from the Mihec group buy a while back? I got the 200gr version, and like it. I've modified hollow point pins on my lathe to mimic this for some of my other hollow point molds too, with good results.
Quote from: Yondering on June 11 2013 11:29:36 AM MDT
heat treated, because it's more consistent than water dropped
A given user may behave more consistently in one method than another, but water dropping from the mold can be just as consistent if you watch your temps and time your drops. I mined this from data collected for a science fair project I helped my son with about 4 years ago. Each line represents 10 bullets tested, pulled from a sample of 30 cast at that pot temp. The "Mold" method were dropped into water from the mold after a count X (I think it was a slow count to 5, but it was many years ago). The oven were heated in a 450 degree oven for one hour on a wire rack, then dunked in water.
| Method | Pot Temp | Avg Hardness | Std Dev | Ext Spread |
| Mold | 650 | 25.88 | 1.05 | 2.4 |
| Oven | 650 | 16.44 | 1.44 | 5.6 |
| Mold | 700 | 29.5 | 1.147 | 4.2 |
| Oven | 700 | 20.46 | 1.23 | 3.9 |
| Mold | 750 | 32.41 | 1.67 | 6.3 |
| Oven | 750 | 24.87 | 1.29 | 4.5 |
As you can see better hardness was achieved all three times via water dropping. A lower deviation, ie more uniform heat treat, was manifest in two of the three.
They key is pot temp and cadence. If you are consistent, your results will be no matter the method.
Quote from: sqlbullet on June 11 2013 03:02:32 PM MDT
but water dropping from the mold can be just as consistent if you watch your temps and time your drops.
True, if you are monitoring your mold temp, but most don't. Mold temp
is the reason water dropping can give inconsistent results. Without having a way to measure the temp of your mold, your results show how even a 100 degree fluctuation in mold temperature will cause a wide spread in hardness. I'd wager that most casters see far more than 100 degree variation in a casting session, hence the statement that heat treating is generally more consistent.
for me water dropping gave me better groups, i was using 12 bh range scrape, water dropped it is about 16 bh
I get better groups from harder bullets as well, with 16-18 being the sweet spot. I think the issue is probably the degree of plastic deformation of the base at 10mm pressures.
I run half clip on, half stick on WW's + 2% pewter
I run my alloy and molds hot and water drop my bullets.
I haven't measured this particular alloy yet, but it works great in high power 10mm and mid level 454 loads
gofastman, that alloy should work out to be about 97% lead, 1.5% antimony and 1.5% tin. It should have a BHN of about 10.5 air cooled, and about 16-18 water dropped. Running hot enough for frosty, small bullets you might get that bhn into the 20's, especially if the pewter is one of the varieties with some copper.
Yeah, that sounds about right, yes there is a trace of copper in the stuff I'm using.
because I cast hot (very frosty) and like to smoke my molds, most of them were designed about .001-.002 oversize