How much BHN is needed for a cast boolit with a gas check?

[tomo]

I'm going to shoot cast bullets of 30-06 at about 2000 fps.
How much BHN is needed if bullet has gas check?

Is there a guide table or chart of correlation between BHN and muzzle velocity?

[Tatume]

Hello Tomo,

More depends on fit than hardness. I shoot wheel weight bullets (BHN 12) to 2250 fps with excellent accuracy.

Take care, Tom

[tomo]

Thank you Tom,
BHN of bullets I casted yesterday was about 15 according to pencil tests.
But I am not sure that how fit they are.
I am going to use a .309 dia sizing die. Do you think I should have .308 die too?
Anyway, they are my first cast boolits for rifle ever. I can hardly wait to shoot them.

[Tatume]

Hello Tomo,

Try the 309 die and see how they shoot. If not satisfactory, go larger, not smaller. There's lots of good advice here on slugging your barrel and chamber too.

Take care, Tom

[lobowolf761]

Thank you Tom,
BHN of bullets I casted yesterday was about 15 according to pencil tests.
But I am not sure that how fit they are.
I am going to use a .309 dia sizing die. Do you think I should have .308 die too?
Anyway, they are my first cast boolits for rifle ever. I can hardly wait to shoot them.
.309 should work just fine. That's what I size my cast bullets to for my .308 win.

[tomo]

Thanks Tom and lobowolf761
Actually I have only .309 sizing die for 308. Anyhow I will try with bullets I made yesterday at first.

[MostlyLeverGuns]

Lee Reloading Handbook #2 has an extensive(?) discussion on bullet hardness versus pressure.

[JonB_in_Glencoe]

This link at the bottom of the castboolits page has some great info about alloys and hardness
http://www.lasc.us/CastBulletNotes.htm
after clicking on it, Scroll down about 1/3 of the way down the page to a chart called:
"Approximate "Maximum" Chamber Pressure For Lead Alloys (PSI)"

But, the short answer is, you should be fine with an alloy that falls into the range of 12 to 16 BHN for the 30-06 at about 2000fps.

If your loading manual has documented pressure listed for starting loads and max loads, that'll help you when guaging what alloy hardness you want.

regarding what size you should size the boolit. .309 should be fine if you have a commercial rifle with a tight chamber. If you are shooting a older military rifle with a worn or eroded throat, I'd recommend sizing to .311

[mdi]

IMHO; Way too much emphasis is placed on bullet BHN. I usually place it a distant fourth behind proper fit, good lube, and bullet design. I too, have driven some "low" BHN bullets to fairly high velocities (in a .357 mag., 160 gr. SWC, plain based, air cooled, WW and range lead, C-Red lube, hair over max load of True Blue, guessing at around 1350-1400 fps). I tried the "formula" for BHV vs. pressure, but got no better results than what I've learned (bullet fit, bullet fit, and bullet fit)...

[DougGuy]

At a bhn of 15, the pressure developed by pushing the boolit to 2,000fps will fit it to the throat and then the bore regardless of what size it is when it is fired.

[44man]

The GC was actually designed for the purpose using a softer lead. It's main function is to engage the rifling at the base to stop skid. Your limits will be where the GC can no longer grip because of lead too soft.
That means testing, no other way to do it and to recover fired boolits is a good idea so you can inspect them. If your boolit wants to go straight and skids full length, the GC has little hope of pulling a boolit into spin. The boolit must start the process.
The GC is NOT to protect the base and it is NOT a lead scraper.

[lobowolf761]

It has been shown that a GC does help decrease leading when using softer lead alloy bullets. I guess that's the same as what 44man just said. You get that skid effect and leading when you push the soft lead at too high velocities.

[Gohon]

The GC is NOT to protect the base and it is NOT a lead scraper.

I can agree with that but I think to a certain degree, one could say the gas check does perform those tasks apart from it's main task as a sort of collateral performance.

[44man]

I can agree with that but I think to a certain degree, one could say the gas check does perform those tasks apart from it's main task as a sort of collateral performance.
The reason a GC helps prevent leading is that it keeps a seal at the base. When it halts skidding gas will not pass it to erode lead.
However I have recovered boolits where the checks are leaded fully. (Not my loads.)
There are two things never to do with checks. One is to have them smaller then boolit diameter and the other is larger. You can run a boolit through a die larger then the boolit and leave the check larger so when you seat, the check will expand brass larger then the boolit so you lose all case tension. Too small and gas can leak past.
If you shoot .431 boolits, the check must also be .431".
A leaded check means it ran over leading because gas leaked past it and leaded the bore. It has NOT cleaned the bore.
My loading is very easy but I have a very tightly controlled process. Once you hold to all, it is no different then poor loading. Nothing sneaks past me.
Been trying to get a picture up with no luck.
The GC has ONE use ONLY, do not complicate things.

[Gohon]

You're missing the point....a GC may be designed for a particular use but that doesn't mean it does not also perform other duties. Nothing complicated by that at all. Gas leakage past the base isn't the only thing that causes leading in a barrel. A bullet that skids as it engraves the lands will lead a bore also.

Dave Scovill played around with a gas check he designed that was similar to the Harvey Prot-X-Bore check except he could place his check anywhere on the bullet. Scovill placed the GC on the forward driving band of a Keith type cast eliminated skidding on this band during engraving, whereas previous tests indicated skidding on the original cast and leading. Pretty much shows that skidding took place before the check even started to engrave.

For those interested what a gas check really does and how it works....here is a good read on gas checks and their use and purpose. http://www.lasc.us/Fryxell_Book_Chapter_10_GCkorPB.htm

[tomo]

Hello folks,
I am returning from my parents house for OBON holiday which is a time when the Japanese traditionally welcome our ancestors' on Aug 13th and send them back on the 16th.
Anyway, thank you for great advices and comments. I don't have the Lee book but I am reading the web page gave by JonB.
I am using new X-bolt 30-06, fired only a thousand, for cast bullets. It is in good condition. I will test various loads at first.

[44man]

I made the tool long ago to place GC's in the mold at any point. Works like a charm.
Set the check in a cavity and with a special punch, punch a hole in the center.
My PB boolits skid about half the boolit but stops near the base. You can see the land marks are wider near the nose. I get no leading at all and go over 3 years without cleaning the bores. Accuracy never changes. I just water drop WW boolits. If I need expansion I cast a softer nose.
WW metal is tough enough to grab rifling.
Here is the setup with a soft nose boolit and front check. 146855
It really does work. I suppose I was fooling with this stuff since before some of you youngsters were born! :bigsmyl2::bigsmyl2:

[44man]

Anyway Tomo, I hope you had a great holiday. The respect you show your elders is lacking in this country.

[jmsj]

Tomo,
It has been probably 40+ years since I have attended an OBON festival but I remember it being a very special time.
I don't remember all the details but I do remember once having an issue with a 30/30 max. load using straight ACWW's. The mold was a gas check design and did fine at the high/middle range but at the very top end I started getting key-holing. Recovered bullets did not show skidding (judging by the rifling engraving on the bullet) but the bullets looked almost like they were bent. I don't know if this was caused by hitting the sand berm or something else. One of the more experienced casters here can probably explain that. Once I backed the load back down things were better.
Good luck, jmsj

[44man]

It is SLUMP. The 45-70 boolit from Lee no. 459-500-3R was found to slump off center and BPCR shooters dumped it.

[jmsj]

44man,
Thanks for clearing that up. Nose slump is the term that came to mind but I wasn't sure.

[tomo]

44man,
Thanks for showing a picture which I have never seen.
Of course, I didn’t know the front check before your post.


Now a day, OBON becomes just summer holiday for the most part of us.
But this is a good time for a lot of families to get together
at their parents’ or grandparents’ house; family reunion.

[tomo]

jmsj,
I will use cast bullets for 30-06 reduced load at first.
I asked Pat to send his checkmaker and it is on the way,
and it will arrive in this week. I will have a chance to shoot
cast bullets by the end of August. I can hardly wait!

[44man]

Might take a little work and thinking, thinking the most important. But you will love cast.
Most of my revolver work was done staring at the bench or the brass in my hand.
We can't see what goes on in the guns so you need imagination.
Testing is important and I have tested every single thing in print.
I record no failures, no need for books full of them.