i bought some pc bullets from precision- work well in my pc 40 carbine. but im wanting to adjust my alloy to suit. i've had no leading with the black pcs. its a special problem, who do you believe. but i think the optimum hardness can be reached. But with powder coat you don't need to do that. The powder coat does it for you.
This is 2 different posts with you saying "optimum hardness or idea"??? That formula for finding the "optimum" bhn is pure BS!!!!! Nothing could be further from the truth. This is nothing more than antiquated thinking that people tried to apply to antiquated processes using alloys and lubes. And even with the alloy/lubes that formula is still BS.
Tin is still king when it comes to alloys and elasticity is the word you should be using not optimum. An accurate cast bullet has to withstand the rotational torques of the short start pressures in the throats of your 40 carbine. The short stubby bullets you use in the 40s&w is a huge +. Leading shouldn't even be in your vocabulary when dealing with coated bullets. The coating has to be either scrapped off or not applied correctly to get leading with coated bullets.
What's wrong with this picture if you were using the "optimum" formula to find the "optimum hardness"???
I've posted that target before, it's nothing more than my blammo ammo load I use in the 44mag for shooting dirt clods @ 100yds. The bullet is a Mihec 640, a clone of the lyman 429677. Easy enough to look up, 11.5gr of unique
In the lyman 50th edition it lists a max load for the 429677/unique at 11.7gr 37,900cup.
A 2005 alliant manual lists a lead 240gr swc/unique at 11.8gr 35,000psi
Just for the heck of it lets call that 11.5gr/240gr 429640 load/bullet 30,000psi.
30,000 / (1422 x.90) or 30,000/1280 ='s 23.4
The "optimum" alloy should be 23.4bhn but I'm off a little bit. Those bullets are 8/9bhn and were doing 1400fps+ in that 14" contender bbl.
That's what's wrong with that picture. It's a 8/9bhn bullet being pushed with a 30,000+psi load doing 1400fps+/. Using a 23bhn bullet would do nothing for the accuracy of that load. It's nothing more than blammo ammo, plain and simple. There's no leading with that load either.
Another what's wrong with this picture???
The bullet used for that target is a 14bhn lee 160tl-2r. I did head to head testing with traditional lubed vs pc. That target is with the green pc'd bullet
That 37.0gr load of h335 pushing that 160gr bullet (165gr with pc/gc) is a 39,000+psi load
39,000/1280 ='s 30.4bhn
No leading with that 14bhn coated bullet. The optimum bhn using the formula is 30.4bhn. 14bhn is doing 1 1/2 moa 10-shot groups doing 2600fps+.
That's 2 different bullets/loads/alloys with 30,000+psi loads. The only thing they have in common is they have enough tin in them to be able to operate effectively with those kinds of pressures.
Tin also plays a huge role in age hardening. No tin/low tin and bullets either won't age harder or have a minimal increase in hardening. Doesn't matter if the bullets are cast and air cooled, water dropped or heat treated. That's why lyman recommends using their #2 alloy, 95/5/5
95% lead
5% tin
5% antimony
Lyman's #1 alloy was 90/10
90% lead
10% tin
Tin got to the point of too much $$$ and antimony showed up on the scene. Ideally you want equal parts tin/antimony
lyman #2 95/5/5 15bhn
My alloy 95.5/4.5/4.5 14bhn
You want an optimum alloy formula you got it, equal parts tin/antimony. You're 98% lead/2% antimony should be 96/2/2.
Adding 2% tin (96/2/2) would give you a 11bhn alloy air cooled and +/- 14bhn water dropped. If you pc those bullets cast from that alloy you couldn't push them fast enough/hard enough in the 40 carbine to have anything fail.
PC is the great equalizer when it comes to cast bullets. With pc'd bullets alloy's take a back seat allowing the pc to open larger windows to finding accurate loads easier along with using low bhn alloys with extreme ranges in velocity and pressure that traditionally cast/lubed bullets couldn't even begin to do.