Bhn ? ?

[hylander]

I am going to start shooting Cast in my 03A3 and 30-30
I have been told I should use a BHN of around 12-14
and that 18-20 is not good
Why ?
I will be using 2400 powder for reduced loads and the boolits will be GC'ed.
I don't Cast so I must buy commercial and most places boolits are 18-20 BHN.
Fill me in Please.

[Bret4207]

The problem with most commercial boolits is that they tend to be made for the convenience of the caster, not the shooter. Hard boolits don't dent as easily in shipment, hard lubes don't melt off or "make a mess". Producing boolits at their "correct for the bore" size (.308-9 for 30 cal) ensures boolits don't get stuck in the throat or cause unduly high pressures. HArder alloys tend to cast easier and produce a nice looking boolit. The problem with all that is that the single most important element to cast boolit success isn't hardness, pretty boolits or lube or how they handle shipping. It's fit, and you can't expect a run of the mill commercial boolit to fit every gun out there. You may get lucky and find a cast offering that fits you guns and doesn't give lube issues while reaching your desired speed and accuracy criteria. Or you may find they don't fit at all and lead like crazy giving shotgun like patterns.

The way many people get around poor fit is by slamming the boolit into the throat with a heavy load of a fast powder. This causes the boolit to swell (we all say obturate, but it's not the correct word, I forget the right one) in the throat. then it hits the leade and is swedged (sized) back down to bore/groove dimensions which gives a pretty good fit. The problem comes in when the boolit is crooked or otherwise hits the bore incorrectly or is otherwise damaged by the powder charge/obturation interchange. Or, sometimes you can't get the boolit to swell enough to force the fit. THat is the problem with harder alloys- they resist the swelling and remain undersized and rattle down the barrel leaving bits of themselves everywhere (leading) necessitating the use of 4/0 steel wool or Chore Boy pad to scrub the remains from the barrel.

That is a laymans (wordy) explanation of why a harder alloy isn't the be all/end all to cast shooting. It's also the basic explanation as to why I'm not a fan of the "obturation" boolit fitting method.

[mooman76]

Contact Bullshop here and he can make you up just about anything you want in a bullet.

[waksupi]

Depends on the velocity you are going to shoot. My rule of thumb is, two Bn points under your velocity target. Example, 2000 fps, 18 bn. 1900 fps, 17 Bn, 1800 fps, 16 Bn, etc.

[runfiverun]

they are more likely around 16 bhn.
finding the measurements for your rifles so you know what you are looking for is gonna help you.
i have and stil use a 4/6 mix that is fairly hard and it works well in the 2400/4895 type loads.
just make sure the nose and body are good fits to your situation.
i.e 300 nose and 309 body.

[HangFireW8]

I am going to start shooting Cast in my 03A3 and 30-30
I have been told I should use a BHN of around 12-14
and that 18-20 is not good
Why ?
I will be using 2400 powder for reduced loads and the boolits will be GC'ed.
I don't Cast so I must buy commercial and most places boolits are 18-20 BHN.
Fill me in Please.

The "old rules" were, you had to match BHN to velocity.

The "new rules" are, you have to match BHN to peak pressure.

Either way, "reduced loads" doesn't tell us anything. Most any 30-06 load of 2400 could be called "reduced" just because you'll use less powder than 4895, even if you end up with a full pressure 55,000 PSI load.

BHN 18-20 means an alloy strength of about 25,400-28,500 PSI. Following the new rules, you should have good obturation and minimal leading (assuming good lube and bullet fit) at 90% of that in peak pressure or about 22,860 to 25,650 PSI.

Look up your loads in Lyman or RCBS or other manual that lists pressures and see if this provides the kind of performance you are looking for. I can't do it for you since you don't even list a bullet weight.

-HF

[HangFireW8]

i have and stil use a 4/6 mix that is fairly hard and it works well in the 2400/4895 type loads.

A 4/6 mix of what, two different lead alloys, if so which two, or are you talking about a duplex powder load?

I've been reloading for over 20 years, if I can't decode your post, imagine being the newbie...

-HF

[454PB]

I use 18 to 20 BHN all the time in .308 win., 30/30, .338 WM, and 35 Rem. Hardness is not a problem, but proper fit and lubrication in the firearm is paramount.

[Gohon]

The "old rules" were, you had to match BHN to velocity.

The "new rules" are, you have to match BHN to peak pressure.

Who's rules are these? Now I can measure velocity but I sure can't measure peak pressure. I can make a wild guess at peak pressure but with so many variables involved that's all it is.....just a guess. Guess I'm stuck with the old rule.

[Recluse]

Depends on the velocity you are going to shoot. My rule of thumb is, two Bn points under your velocity target. Example, 2000 fps, 18 bn. 1900 fps, 17 Bn, 1800 fps, 16 Bn, etc.

Okay, THAT'S a pretty danged good way of approaching BHN.

(Shaking my head) Never ceases to amaze--or humble--me that no matter how far down the road you've traveled, there are always those who've traveled further, or seen different sights along the way than yourself.

Thanks for sharing that.

:coffee:

[hammerhead357]

Hangfire I don't want to start something here but I have been reloading for 32 plus years and casting for 27 and I couldn't decifer Waksupis 4/6 alloy either but there are better ways of asking about it.

Waksupi what 4/6 mix are you using. 4 to 6 lino to ww or what? Please specify...

Hangfire Waksupi has been around a long time and has lots to offer lets try not to upset him. Perhaps I took your post wrong if so please forgiveme....Wes

[Rocky Raab]

Waksupi's rule is excellent if you don't know the pressure.

If you DO (you are using load manual data and they list a pressure), then a usable rule of thumb is BHN = pressure/1200. Example: expected peak pressure is 24,000 psi (or CUP; for this use it doesn't much matter), so the desired BHN would be about 20.

Or you can use that rule in reverse. For a bullet that is claimed to be BHN 16, you can expect to load to not much more than 19,000 psi/CUP. Scan a load manual for a powder and charge that stays there or a bit less and simply accept the velocity that results.

BHN aside, however, it is also true that proper fit and a proper lube are equally important - or more so.

[runfiverun]

a 4/6 mix is 4% tin and 6% antimony.
most always an alloy will be expressed in didgits such as 2/6/92 [terracorp magnum]
4/12/84 [lino]
and i don't particularly buy into the bhn has to be x either.
might as well use the 1422xbhn for pressure guessing.
i have checked the x1422 and used that number as a beginning pressure, instead of a premium or maximum.

[waksupi]

Hangfire I don't want to start something here but I have been reloading for 32 plus years and casting for 27 and I couldn't decifer Waksupis 4/6 alloy either but there are better ways of asking about it.

Waksupi what 4/6 mix are you using. 4 to 6 lino to ww or what? Please specify...

Hangfire Waksupi has been around a long time and has lots to offer lets try not to upset him. Perhaps I took your post wrong if so please forgiveme....Wes


I didn't even say anything about 4/6! :D

[Rocky Raab]

runfiverun's post make me wonder if I mis-remembered that rule of thumb formula. I mentioned pressure/1200, but it could well be that pressure/1400 is better or more appropriate. Using 1400 would give a lower BHN number, and a softer bullet that obturates better (yes, obturate IS the correct word).

[Master Mariner]

can anyone give the Rockwell equivalent of Brinnel ?[COLOR="Red"]

[runfiverun]

i don't think rockwell and brinell are linear.
it's like using a saeco tester and a chart.
there might be a correlation but not linear.

[Old Goat Keeper]

Rockwell and Brinell are definitely NOT linear! In another life time (pre-retirement) I used both scales in materials testing.

Tom

[HangFireW8]

a 4/6 mix is 4% tin and 6% antimony.


Thanks for the clarification... and my apologies (to you and waksupi). :-D

-HF

[hammerhead357]

Sorry about that Waksupi put the wrong name to that one. Should have been rfr....Wes

[Recluse]

Thanks for the clarification... and my apologies (to you and waksupi). :-D

-HF

Hell, I knew what you were saying. :)

If some of us that have been doing this for as long as we have didn't understand a formula or theorem, how in the flaming cats hairs is someone fairly or brand new to casting supposed to understand? :veryconfu

I also like Rocky's explanation, even though it calls for some mathematics which I enjoy about as much as listening to CSPAN during the Pelosi/Reid Hour.

But seeing as how I'm working up some fairly hot 30-06 200gr loads here this week, Waksupi's formula is perfect and will be very helpful. Already have the alloy made up--high in tin, extra lino--but not enough to make it too brittle--and will be doing BruceB's soft-nose pouring method.

I'm wanting to get me a 200 - 300 meter hunting load with this boolit--got all spring and summer long to work on it and test it. Life is good.

:coffee: