Bhn vs velocity vs pressure

[jonp]

Ive read lots of threads and stickies on matching bhn to velocity but was wondering if anyone matche bhn to pressure instead. The lasc site has a paragraph on the front page about it and it would seem to be an interesting idea on how to pick a powder not only on velocity wanted but also pressure generated. This would narrow it down better i think.

For example i have some coww boolits to use in my 45acp. At 12bhn the formula suggest a little better than 17,000 psi is needed for the boolit to properly obdurate and seal. In my lymans this indicates a near max charge of unique as say red dot does not get there safely.

Any comments on this method?

[ubetcha]

I believe the latest edition of the Lee Modern Reloading book has a section on BHN vs pressure. Last time I looked at it, I just skimmed through it, but now that I have a 357 max , I want to find out if I can get by using an alloy of water dropped 50/50 soww/coww + tin. I also want to try that alloy in my 30-30 too. Both calipers will be used in a T/C. One 14" Contender(30-30) and one 12" G2(357max) for silhouette matches. I will have to re-read the book and try to understand it better.

[waco]

I believe the latest edition of the Lee Modern Reloading book has a section on BHN vs pressure. Last time I looked at it, I just skimmed through it, but now that I have a 357 max , I want to find out if I can get by using an alloy of water dropped 50/50 soww/coww + tin. I also want to try that alloy in my 30-30 too. Both calipers will be used in a T/C. One 14" Contender(30-30) and one 12" G2(357max) for silhouette matches. I will have to re-read the book and try to understand it better.

Yep. Grab this book. Lots of good info. Lee modern reloading II

[44man]

No pressure is needed to make the boolit obturate if it fits the gun. Last thing to look for.
The most important thing you need is an alloy tough enough to take the rifling with no skid.
Fast powders that peak fast are harder on a boolit then a slow powder. The final pressure does not matter much if the boolit is started before peak.
It has been hard to explain that even though fast powder pressures are lower, it is delivered to the boolit RIGHT NOW. That boolit has a hard time starting to turn.
Those BHN/pressure charts are mostly wrong because the chart should be made for every powder used in each caliber.
I found the best way is to catch boolits to inspect. Any alloy that shows larger marks on the base then the rifling is rejected.
The question of a 50-50 alloy! I have oven hardened 50-50 but PB will not group, need a GC but you will still get a few fliers. The lead will skid and the GC still has a hard time halting it.
Recoil can be reduced with a slow powder without reducing the charge too. Just change powders. I was beat in the face with 4198 in an old Trapdoor 45-70. Changed to 3031 and it all went away and accuracy was a ragged hole at 50 yards, point of aim too. That testing also went from a 405 gr to a 500 gr boolit. The 500 was a joy to shoot with 3031. The owner took a lot of deer with that load.
I tried Unique and all other powders in my 45-70 and 30-30. Went to 4759 in the BFR 45-70 and 3031 in the 30-30 Marlin, neither has much recoil but accuracy you can't beat.
I use only water dropped WW metal and get 1632 fps from the 45-70 revolver and 1903 fps from the 30-30.
The .357 Max is a high pressure round and will love 4227 powders. Fast thump so make the boolit harder.

[HangFireW8]

What 44Man said. When I first started casting I followed Lee's pressure rules religiously. Then I found out I had accidentally violated the rule with excellent results.

Think of the pressure rule as a starting point, not as a law of nature.

[Larry Gibson]

The BHN to pressure charts and formulas do not work because they address the peak pressure only. It is the rise (1st part of the time pressure curve) to that peak pressure that counts and it is not addressed.

With a bullet of given alloy, lube and fit with the same peak psi you can have very poor accuracy using a fast burning powder and yet very good accuracy using a medium or slow burning powder.

Also even with a bullet of given alloy, lube and fit with the same peak psi if that psi is not high enough for the powder to ignite and burn efficiently it probably will not be a good load.

Larry Gibson

[mdi]

I seem to be in good company with my thoughts on BHN/Pressure. I tried the formula a few times and found that when my bullets fit my gun, all the figgerin' and calculatin' has no effect on my cast bullet's performance. I got no leading before I applied the formula, and I got no leading after the formula was used. I get good accurate bullets cast with my "shootin' alloy" and I got no better results after application of the formula...

[OuchHot!]

I recall first reading about the bhn/pressure relationship for revolvers better than 20yr ago. I suspect that part of what might have contributed to these conclusions is there was very little written about FIT and very few revolver molds made to order. The bpcr guys figured out fit real early and using bp could do a remarkable amount of shooting without leading (fouling maybe) really building up. The other aspect is that as Larry G. and 44man point out, pressure was only tabulated in peak numbers, either copper crusher or transducer. It is not totally relevant to talk about pressure until you have the pressure Vs. time curve and relate that to where the bullet is in its interior path. Nowadays, the molds are held to better tolerances and we understand the need for FIT and can achieve it. People that shoot over snow or into water have been pointing out the skidding aspect that 44man references. The alloy has to withstand spin up or you need reinforcement (gas check).

[462]

I have a .44 Special load that shoots very accurately and without a trace of leading. For the fun of it, I used the pressure/velocity/BHN formula and it resulted in a negative BHN number. (Did the math a number of times, to be sure.) The first and last time for that idea.

[John Boy]

Took less than 2 minutes for this information on (http://www.lasc.us/ChamberlainLeadToughnessTesting.htm)http://www.lasc.us/CastBulletNotes.htm

http://www.lasc.us/ChamberlainLeadToughnessTesting.htm
http://www.lasc.us/SAAMIMaxPressure.htm


Bullet BHN / "Minimum" Chamber Pressure For Lead Alloys (PSI)


The formula (from the pages of HandLoader Magazine) to determine at what pressure an alloy of given BHN will obturate the base of the bullet and seal the bore. If the bullet is too hard to obturate, gas cutting usually occurs on the base band on the non-driving side of the rifling and barrel leading is likely. Simply multiply the alloy BHN by 1,422.


Example: Alloy BHN of 12 multiplied by 1422 = 17,064. An alloy of 12 BHN should be used with a load that develops a "minimum" of 17,000 psi. Need more info on minimum / maximum alloy BHN? These Glen E. Fryxell articles explain
alloy BHN in easy to understand language.




Approximate "Maximum" Chamber Pressure For Lead Alloys (PSI)


Plumbers lead, stick on WW

13,000 - (Black Powder Only)


Wheel weights / clip-on




25,000 - Non-Magnum handgun


loads, Rifles to 1,900 fps










Lyman # 2 (alloy varies in




Lyman cast bullet books)









35,000 - Magnum handgun &


rifles to 2,000 fps










Quench-cast WW (dropped




from mould into cool water)









48,000 - Magnum handgun


& rifles to 2,200 fps






Oven heat treated WW




55,000 - Jacketed velocities in handguns


and rifles with quality bore & balanced load

[melloairman]

Some of us shoot with out bullets obituration all the time .Marvin
http://castboolits.gunloads.com/showthread.php?225068-Engraved-bullets

[MtGun44]

High pressure .44 and .357 Mag loads with 8 BHN boolits work fine for me. I think Larry has
the handle on the issue of why it works. I have tried the water dropped hard stuff and find nothing
there that interests me. Less expansion, more work, same or worse accuracy. Seems like a
waste of time to me. Plain old air cooled wheel weights is my standard, use GCs in rifles and
plain in all pistols. Sometimes I use range scrap that runs 8 BHN and it seems to work just fine
in my pistols, not yet tried in the rifles.

Hard is generally not necessary for high pressure loads - so I think that Lee's claims are bogus.
Larry may have it - that the rate of rise is the issue, not addressed by peak pressure only.

Bill

[44man]

Larry and Bill have it. If you use Bullseye, 231 or Unique in your .44, you need a harder boolit then with 2400 or 296.
Any lead will still "bump" up when slammed but soft can skid. Nobody told the boolit that it has to turn so it wants to go straight. Soak boolits in shine so they stagger. :veryconfu
When I started with the .44 in 1956, I air cooled but used only 2400, had great accuracy and was shooting well over 500 yards. But WW's were better back then too. Now they recycle with all the junk from stick on's to zinc. The powers that be claim a WW off the road is poison.
I need to ask, how many weights has anyone found on the road unless there was a crash? Even then they don't pop off. I found one once in a parking lot.
The EPA discovered we make boolits so they don't want lead. Back door gun control.