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-   -   Cast Bullets, Obturation (http://www.firearmstalk.com/forums/f30/cast-bullets-obturation-34206/)

patret 11-10-2010 05:06 PM

Cast Bullets, Obturation
 
Cast bullets must perform a function called "Obturation" when fired. This process causes the cast bullet to expand in the barrel preventing gas from leaking around the base of the bullet thus causing leading. Obturation is always a issue when I cast bullets because the alloy "BHN number" must be designed to the powder charge. For example, a light charge requires a cast bullet to be a BHN number of 14 or less. Most commercial cast bullets are cast to a BHN of 24 and will lead the barrel with a light charge.

A good bullet caster will have a BHN tester to check the alloy hardess. Hard cast bullets will not make good target loads because of the typically light charge.

Some pistols and a few rifles are not designed to shot cast bullets. The Glock pistol and the Micro-Groved barrel come to mind. There are others with rough barrels that will lead.

Patret

quigleysharps4570 11-10-2010 06:32 PM

I use the Saeco lead hardness tester...right handy to have around.

BILLYBOB44 11-10-2010 10:58 PM

Cast bullet hardness tester??
 
You're right, Pat. Cast bullet hardness-or lack of it is important. My "tester" is mounted to the end of my finger/thumb. If it takes good/moderate pressure to scratch the base of a bullet, then it is just right.:confused:
For those out there that buy cast bullets-Brad, at Missouri Bullets, is one of the best at providing the proper BNL bullets for a fair price.
I have ordered/shot more than a few of Brad's 500 packs of bullets, and can say that he and his family run a great operation and have SUPER fast shipping.
Google up: Missouri Bullet Company and check them out..Bill..;)

jpattersonnh 11-10-2010 11:10 PM

Is the OP passing info along or ????
I can say that I have never had a leading issue using cast lead in pistols or Rifles that use pistol calibers.
Not sure what the intent of the post is. Maybe new to casting, a warning?????
Am I missing something???

BILLYBOB44 11-10-2010 11:19 PM

Lead wash can be a problem!!
 
:)
Quote:

Originally Posted by jpattersonnh (Post 384072)
Is the OP passing info along or ????
I can say that I have never had a leading issue using cast lead in pistols or Rifles that use pistol calibers.
Not sure what the intent of the post is. Maybe new to casting, a warning?????
Am I missing something???

You think the OP has been "Glocked"??:eek:
It could be that he has been washing out lead from the barrels of his shoot'n irons?
It may be just for general info??:D

jpattersonnh 11-11-2010 12:04 AM

Quote:

Originally Posted by BILLYBOB44 (Post 384077)
:)

You think the OP has been "Glocked"??:eek:
It could be that he has been washing out lead from the barrels of his shoot'n irons?
It may be just for general info??:D

Don't know which or why? I've been shooting lead for many years. Just an odd thread. It is why I asked.

Highpower 11-11-2010 12:56 AM

Quote:

Originally Posted by quigleysharps4570 (Post 383934)
I use the Saeco lead hardness tester...right handy to have around.

+1 on the Saeco.... :cool:

stalkingbear 11-11-2010 09:12 PM

What he was saying is the bullets have to upset to seal the bore. If bullets are too soft or too hard you'll have leading issues. It's important to know how soft/hard your bullets are before trying to drive them very fast or even too slow for the lbn (hardness) of the bullets. Most people know that the harder the bullet is the faster you can drive them within a reasonable speed. What a lot of people don't realize is you can drive a hard bullet too slow as well. I work up my loads to match the lbn of the bullet I'm loading. Patret has been loading & casting for 40 years that I know of and I've found him to be very knowledgeable.

res45 11-12-2010 02:35 AM

You also need to take into account bullet dia. as well as BHN. A cast bullet to small in dia. will lead your bore no matter how hard or soft it is.

Obturation/BHN only goes so far till the load pressure overcomes the alloy and melts the base,even very had alloy bullet need a gas check at some point to withstand the pressures and keep from melting the bullets base.

As far as shooting lead as in cowboy bullets in polygon barrel that's definitely a problem. However shooting hard cast bullets that fit the bore and using a good lube are not a problem. I know many casters that shoot hard cast bullets in Glocks and I've shot many a 95 gr. Lee RN cast bullet out of a CZ-82 with no leading issues.


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