Understanding BHN

[redneck44]

Trying to understand this BHN thing before I order bullets for 44 Super Blackhawk. My Lyman 49 manual says I should shoot Linotype, 22 BHN. Most of what Ive been seeing online is about 16-18. What is the difference in the numbers? I guess one is harder then the other, is that right?
And how would a lower number BHn affect my handgun?
Thanks for any advice offered.
Doug In Pa.

[Bullshop]

Lower BHN will allow obturation for all important gas seal at lower pressure/velocity loads. Save the lino for rifle bullets and even for that I would blend with softer alloy then quench if hardness is needed.
For plinking type loads in a 44 mag bhn-10 is about the right area for hardness.

[Bullshop Junior]

I shoot straight ww from my 454 all the time at about 11 BHN

The lower the BHN number the softer the lead.

[redneck44]

IS a lower number more apt to foul the barrel, then a higher number?
And forgive me, but what does obturation mean?

[bangerjim]

Much research has been done in the past decade about hardness and the need for it. Most of the loading data out there (including the Lyman book) was compiled and written decades ago and everything revolved around Lyman #2 and Linotype, two very common alloys then readily available. In the intervening years, many in this sport/hobby have found that softer is better.......as stated by Bullshop and to conserve now expensive Sn and Sb alloys.

More than hardness is FIT to your barrel! Today FIT IS KING! Too hard is just as bad as too soft when it comes to leading and accuracy. With the correct size of slug, you can get optimum performance with softer alloys. You need to slug your barrel to find the size of boolit you actually need. If you cast your own, you have much more control over that.

I shoot all my subsonic slugs at 9-10 and PC them. Rifle boolits are cast at around 14-15 and PC. I use Cu GC's on those. No leading.....EVER.....and very good performance all around.

Check the LASC site for excellent info on all things bollit!

Have fun shooting!

bangerjim

[Sgtonory]

IS a lower number more apt to foul the barrel, then a higher number?
And forgive me, but what does obturation mean?

It is all about fit. If the boolit dose not seal the gases then there is what is called gas cutting. And this is a major cause of leading. I shoot softer alloy out to 1500fps around 11-12bhn for my 44 mag carbine and no leading at all. But i also size my boolits to .432 and not .430

[Bullshop Junior]

IS a lower number more apt to foul the barrel, then a higher number?
And forgive me, but what does obturation mean?

Depends.

How fast are you pushing them?

It higher velocity the softer lead will be more prone to leading, although at lower velocity it could be the other way around.

Fit is everything. And good lube.

Obturation is Basically the bullet swelling to fit the bore.

[bangerjim]

Yes.......obsturation is just a $10 word for expansion in the barrel. As the powder burns/explodes and pushes on the backend of the boolit, it pushes the sides out and into the barrel and rifling, forming a temporary seal to give the push to the projectile. If that seal is not optimum, you get blow by/gas cutting and loss of performance........and potential leading big time.

Again......take a few hours and read the LASC.us site for tons of excellent technical info.

bangerjim

[Bullshop]

In a revolver you need to pay attention to cylinder throat diameter as much as barrel diameter. In a revolver the boolit has to make that gas seal before it ever gets to the barrel. Mike your cylinder throats and go with that diameter or .001" over that diameter.
Obturation is the bullet giving somewhat under pressure to press outward against the cylinder or barrel walls with the same amount of pressure that is pushing the boolit and so sealing the gas behind the boolit and not allowing the gas to pass by the boolit and there by causing gas cutting and leading the barrel.

[redneck44]

Wow, lots of good advice, maybe I can get a handle on this in time.
Thank you all. Bullshop you have a p.m.

[emrah]

All of my boolits are straight stick on wheel weights. I shoot .45 ACP, .38 Special and .30-30 cast boolits. The .30-30 boolits have a gas check.

I size them to .452", .357" and .311" respectively. I get absolutely ZERO leading with any of them. I can push my .30-30 to over 1800 fps before I start to see leading. And that's just lubed with Lee liquid alox.

Fit is everything. The term "hard cast" makes me cringe! Shoot for .002 to .003 over groove diameter if possible.

Emrah