Lead bullet hardness

I was shopping for coated lead bullets at Missouri bullet company and noticed that the bullets marketed for BE use have a lower/softer brinell Rating of 13 while the same bullet design marketed for action shooting has a brinell of 18. 

Is the softer bullet better suited to BE use? 

If so, why? 

Thanks,
-Trevor

BE is generally shot at a lower velocity than steel plate banging.
Probably to reduce leading at higher velocities

Action shooting like IDPA have power factors to meet which is like Jim says. So they need a harder alloy to prevent gas cutting in the barrel causing severe leading and poor accuracy. BE shooting has no power factor to meet, so can't use a harder alloy as it wouldn't obturate (expand) at lower power and seal the bullet against the barrel which would cause gas cutting of the bullet. So it's the ability to seal which makes the difference in hardness.
 I cast my own and use indoor range scrap which has a hardness around 11 bhn and I tumble lube with liquid 45-45-10 it's a great combination for me, accurate and no leading. 
 Stan

Bullet fit to your barrel trumps hardness.  I regularly shoot old falling block rifles with plain base bullets that are cast 30-1, pretty soft.  My velocities run 1400 + or - and do not experience leading.  However, the bullets do fit my barrels.
Phil

Missouri Bullet Company has a good explanation on their web site-

Missouri Bullet Company

Yes it does Phil, I use our range scrap in my 1903A3 at little over 1400 also and bullet fit is most important. The OP wanted to know the difference in hardness for the 2 disciplines, but bullet size is important for good sealing for those that cast for ourselves. Groove size is one thing but chamber size has to be right also.
 Thanks for reminding us Phil. 
 Stan

I notice MBC also offers grooved vs non-grooved coated bullets, such as the 200gr SWC. Is there a general consensus about when to use one vs the other?

Grooveless are preferred for feeders… 

As for hardness, it was the understanding that hardness generally dictated max velocity.  Roughly speaking  BHN 5-7 (Swaged Lead) 900 fps, BHN 9-12 1100 fps, BHN 18 (92-6-2) 1600 fps, BHN 22 (Linotype) 2200 fps.  These are for lubed (Alox) bullets.  For coated bullets there isn’t enough info, but it seems that coated can be pushed faster than the limits above, but the data is only anecdotal.

PMcfall wrote:Bullet fit to your barrel trumps hardness.  I regularly shoot old falling block rifles with plain base bullets that are cast 30-1, pretty soft.  My velocities run 1400 + or - and do not experience leading.  However, the bullets do fit my barrels.
Phil

This!!!
Bullet diameter should be .0005-.001 over groove diameter. A BN OF 9-11 is great plenty for our velocities. If you ever want to have to go lead mining, just run a hard undersized bullet down the bore. Used to run into that early on until I started casting my own and paying attention to the bullet/barrel fit. 

Al

Way back, when Keith was preaching about hard cast fat nose SWC's in revolvers, I had some leading issues in a couple guns. One was a Colt SAA 45 I bought brand new in 1980. The then new Federal SWC-HP load leaded it pretty bad. And none of the handloads I tried with hard cast bullets did any better. Eventually, articles started mentioning bullet fit to the bore and cylinder throats. From memory, that Colt had .457 throats, and I don't think ammo loaded with .458 bullets would have fit.

Moving on, my SW 929 9mm has .357 throats, and it leads with .356 cast bullets. I've loaded some .358's, and it seems to be ok, but haven't had a chance to shoot it much.

And there's the 16-4 32 HR with .314 throats.