Correct BHN x Bore x Velo ?

[stevemb]

There is a correct range of hardness for an application. "Hardcast" is not automatically best. What constitutes "hardcast" itself, can be debated.Many here know WAY more than I. I am just throwing out the subject here. I think this subject can stand some discussion. Lets assume you have the correct diameter for the gun in hand. I've recently bought "softer" 205gr RNFP's from Matt's Bulles for my Ruger Sheriff and Bulldog .44spec's.. Also some similar from Black Dawge for blackpowder use. Actually look to be the same bullet but different lubes. Wonder how close they are in BHN ? Matt's for special use, cowboy use, the Black Dawge's definitely on the soft side. But the same ? I do not know. Just curious. So many ask for, specify they want "hardcast" bullets. Yet at what velo. are they really needed or wanted ? Can someone here guestimate from experience what BHN's for BP/cowboy use, what for middle-of-the-road everyday loads, and then what for magnum handgun velo's ? Can we break it into only 3 classes ? I'm all ears here. I try to get the correct bullet for the use. Think y'all are too.

 

[Rclark]

Correct BHN has to do with 'pressure' not velocity. Of course higher velocity means more pressure but...

The 'formula' is PSI / 1400 = optimal BHN

So for .45 Colt at 'max' SAAMI pressure of 14,000psi we get 10 BHN as 'optimal'.

As Iowegan (a gunsmith on another forum) puts it "Matching bullet hardness to chamber pressure is the key to accurate and foul free loads. The concept is simple .... it takes a given pressure to force a bullet to
obturate (bump up in diameter) . The higher the chamber pressure, the harder the bullet must be."

I use 12-15BHN for all the .45 Colt loads that I use (from 700fps to 1100fps) . I have found that BHN can be a bit flexible as I don't get leading using these bullets (in my guns). However I will not use 18+ BHN in .45 Colt as that is 'way' over hardness for the pressures generated. Really the BHN is a 'rule of thumb' not an absolute. If the bullet diameter is correct, the throats correct, the throats are lined up with the bore, the barrel is 'perfect' (smooth, no high, low spots, and is slightly tapered from back to muzzle), then any hardness of bullet will work.... Within reason of course. If you try to shoot pure lead, for example, at 1600fps, the bullet won't hold the rifling and will 'skid' in the bore and cause leading.... A harder bullet is in order... Using the BHN formula above should give you a 'clue' of where you should be!

Bullet fit also plays a part too as bullets should be .001" above groove diameter as well. Which means the throats should also be .001 to .0015 over bore diameters as well! Otherwise if the the throats 'squeeze' down your properly sized bullets ... and the proper diameter does you no good! Since Ruger .45 Colt barrels are all .451, throats should be .4525 and bullets .452 .

 

[stevemb]

I hereby claim a new record has been set ! A thread started, a question asked. Well answered after only two replies. Certainally I'll read ALL replies, sometimes a different wording or point of view makes something click. Thanks guys.

 

[Bucks Owin]

Excellent reply by Rclark...Pressure not velocity! :wink:

I would just add that in the case of overly large throats that regardless of groove diameter, bullets should fit the throats as closely as possible. My '74 NM .45 BH may have a .4515" barrel but since it's throats come in .455+" I get best accuracy with .454" cast bullets...

 

[stevemb]

For 57K, or whoever might know. What is the BHN of swaged bullets ? Common sources now ?

 

[SweetWilliam]

The 'formula' is PSI / 1400 = optimal BHN
Is the 1400 used for all calibers?

 

[Cheesewhiz]

5 to 6 is a standard for swaged blanks for jacketed bullets. I have some IMI bullets that are bare swaged lead and they run about the same. Hornady's swaged bullets are very soft, around the same. I know you can swage bullets up to 10 BHN after that there is crumbling going on when cold swaged. The hard cast that I buy are normally on the 15 -17 scale, some claim it is run that high to protect from damage in shipping. No one likes beat up bullets.

 

[Rick Courtright]

The 'formula' is PSI / 1400 = optimal BHN
Is the 1400 used for all calibers?

Hi,

As far as anything I've ever read says, the answer is yes. And don't be surprised if you see some articles use 1422 for the real picky reader. There's no significant difference for our purposes (BHN with lead bullets isn't an exact science), and 1400's easier to remember!

Rick C

 

[308 Scout]

When I got hard and heavy in to bullet casting, I was using ACWW for everything in my .44 Specials and I mean from 700 fps, low pressure CAS loads all the way up to Elmer's load of a 260 gr. SWC @ 1200 fps. Then I began casting HP's from softer alloy in the 8.5 - 9.5 Bhn range and guess what? No leading and accuracy to boot! So just like Rclark said, there are no absolutes.

Now, as to your Bulldog. I bought one a few months ago and presumably due to the rifling with rather shallow grooves, it WILL NOT stabilize soft bullets at any pressure. I started out trying some cast wadcutters from a 429348 mould cast around 9.0 and they literally struck the target sideways. Same for a 247 gr. SWCHP. Just this afternoon I tried some 220 gr. RNFP's with the same result. But cast the same bullets out of ACWW at 12 - 14 Bhn and the little revolver will shoot 2" - 3" offhand groups at 15 yds.

 

[stevemb]

308Scout, thank you for the Bulldog specific info..