Let's see if I understand this...

[jamesgpobog]

For me, the aspect of optimum Brinell for cast bullets is a rather new subject, but I think I understand it.

Different Brinell hardnesses obdurate at different pressures, so (at least theoretically) leading can occur with both soft and hard cast bullets if the Brinell does not match the proper CUP (derived by the formula Brinell x 1422 = CUP).

What I think this means in terms of reloading is that buying a box of whatever bullets and deciding 'I'm going hunting, i need to load up 50 rounds hot', while next week loading the same bullets for light load target practice with a 2" snubbie is not the way to keep lead out of your barrel.

A more proper thought process would be "I want 100 rounds of zombie-killers. Here's a 158gr RNHP at Brinell 10, so I look and see that Clays gives me 14400 CUP with 3.2 grains, and 827 fps.

So if 14400 is the minimum obduration pressure, what is the maximum pressure or speed for that bullet?


Or am I overthinking this?

[Tycer]

In my limited experience that holds true for revolvers. In rifles, my experiments show that hardness at speeds less than, say, 2000 fps, has little to do with leading if the bullet fits the gun. I base my bullet hardness strictly on the terminal performance desired. Getting bullets up into jacketed speeds seems to require a harder bullet although that's based on others' material rather than much of my experience talking. I have found that for hunting, I like the results of a hard flat nosed bullet hitting the game at 1400-1800 fps.

[Griff]

The following is my thinking on the subject:

Leading a barrel, whether rifle or handgun is a matter of several factors. First and foremost IMO, is bullet fit to the barrel. Even a poorly fit "hard" bullet will leave lead in a barrel, even at relatively slow speeds... as hot gases can and will melt lead from the round the side of the bullet, depositing such then molten lead on the lands or grooves.

Then, with proper bullet fit to the bore (groove diameter + ~.002"), comes the combination of velocity and bullet hardness. I don't run anything that is made of pure lead without either a cotton or paper patch thru any rifle. With handguns, this is less than a moot point... for my purposes, and any pure lead I shoot out of a handgun will be pushed by black powder. While I'm sure there is a scientific reason for the failure of BP loads with soft lead projectiles to lead a barrel... I'm not conversant enough to discuss, let alone try to explain.

Wtih smokeless powder, it becomes a balancing act as to how fast one can push a bullet without leading the barrel. I use the general rule of thumb that lead bullets at around the hardness of Lyman #2 will not lead until pushed above 1400fps. I don't cast that soft normally. I run my 350 grain .40 caliber bullets in my Shiloh Sharps about 1700fps using straight wheel weights and haven't had any leading with either smokeless (5744) or BP as a propellant. Straight wheel weights on my tester register about 15Bhn. I've run cast bullets as hard as 21-22Bhn and as fast as 2200fps without any leading. On those, I also gas-check them... For rifle loads in that 2200fps range I generally keep bullets at about 18Bhn, any harder and they tend to shatter on impact. NOT what you want in a hunting load.

[Pisgah]

No bullet, at any time, obdurates. They do, however, sometimes obturate.

[Sixgun]

No bullet, at any time, obdurates. They do, however, sometimes obturate.

Hey,hey....are you trying to steal my "comedian" status?

I believe most people think too much on the lead hardness thingy. I've been casting for 40 years and literally untold amounts of revolvers and rifles during that time and as long as you size the bullet to fit the cylinder throat for revolvers and a thousandths over for rifles, good old wheelweight material will be good for around 15-1600 fps in rifles and 12-1300 in revolvers, and you only need to add about 2-4% tin to the wheel weights if you want to go to 1800 in rifles and even then, that sometimes is not necessary. A good lube is also a must.

After 1800, other factors come in and it would take a book to tell them all.

There's a million other variables that come into play, but generally speaking the first paragraph will get you by 95% of the time.----6

[missionary5155]

Greetings
Been around bullet casting since I was 4. My dad and his Navy buddy were the instigators. As stated above by at least 3 responders bullet fit is number one. Oversized is always better.
For rifles the throat area is principle. An example is a 1907 made 1892 44WCF SRC Winchester about 8 feet from me. The throat area is fat. .435 as best as I can get it measured. The bore near the muzzle is .430. Many people would assume a .430 lead hard cast bullet would be perfect. Actually a very soft .436 bullet would be great but it will not chamber. So I use a .433 diameter bullet (max diameter that will chamber) 220 grain Saeco 443 made of range lead (soft). I do get minor lead smears in the throat area but no where else. This is with 8 grains Unique. If I add COW( cream of wheat) filler the "smears" disapear. 9 grains Unique reduce the smears a tad but the 8 grain load is much more accurate.
Results are near the same with pure WW but the throat smears are a bit worse.
Old Winchesters are notorious for fat throats. Marlins no better. But then they had to deal with BP loads fouling throats so fat throats was a simple solution. Accuracy suffered a bit.. but a rifle or SRC that would not chamber the third shot was worthless.
50-50 mix bullets are my favorite hunting projectile. I have yet to need to shoot a corn cruncher twice so even if there is a bit of leading it means nothing. 50-50 will expand at most any lever rifle velocity. It will not shatter on bone. It will leave a nice exit hole to leak out qiuckly.

Revolvers for me are the same. Fill the chamber mouths and usually all is well. But with revolvers you may have to do a ballancing act. If my cylinder mouths were .431 and the barrel was .429 (1903 vintage Colt New Service 44 WCF) I found .431 to shoot better than .432. But generally I plan on .001 over mouth diameter bullets for revolvers.
With revolvers you need to check all the mouths as sadly some vary badly. Finding some that vary .001 is all to common. But sometimes a .003 can be found on one. That means that bullet runs higher pressure in that chamber plus will probably be a loose fit in the barrel. That is real bad. To me the perfect revolver has all cylinder mouths .001 over the bore diameter.

Should you want to get a very good education on lead projectiles I highly advise the Castboolit site. It is all about lead and putting it on target.
Mike in Peru

[jamesgpobog]

No bullet, at any time, obdurates. They do, however, sometimes obturate.

Hey, I'm new to all this. I'm gonna kick the butt of the guy who sold me that word for $10...