7
by CowboyT
Oh, I avoid those "hard cast" bullets, generally. The problem isn't velocity. It's pressure and proper bullet lubrication. I've shot cast bullets many times through rifles at over 2,000 ft/sec without leading problems.
Here's the explanation. With cast bullets, you need to do three principal things.
1.) Match the bullet hardness to the pressure of your load.
2.) Use proper bullet lubrication.
3.) Make sure you're using the best size of bullet for your chamber and barrel.
Let's deal with pressure first. The major issue here is that you need to get proper bullet obturation to get a good gas seal and prevent something called gas-cutting. That means your load's pressure has to be able to squash the bullet enough to accomplish that obturation, without being too much. Fortunately, getting that match is pretty easy to do, and the alloys are pretty forgiving, within certain ranges. The harder the lead alloy, the more pressure you'll need to obturate that bullet.
I happen to have Lyman's 49th as well as the newest 51st. Looking at Lyman's 49th, the average starting pressure for the 125gr JHP is 27,500 CUP. The average max pressure for that same bullet is 39,817 CUP. Gotta love spreadsheets. :-) So, if you have a "mid load", that tells me you're at a pressure of approximately 33,600 CUP. For that pressure, real-world experience with bullet casting tells me that you need a bullet hardness of about BHN 10-12, basically the hardness of wheel-weight lead. BHN 15-16 would be borderline, and anything harder than that certainly would result in lead-fouling to some degree.
Next, we tackle bullet lube. Those hard-wax bullet "lubes" that the companies put on their bullets? They're USELESS. They might as well not even bother lubing the bullet. That wax is too hard to do a good job of lubricating the barrel during the bullet's passage down it. Leading is the result. Been there, done that, not interested in buying the T-shirt. You need softer lube. Good choices are the good ol' NRA 50/50 formula and its variations, and Liquid Alox, which is what I use pretty much exclusively. Both are available from LsStuff.com (they use the name "Liquid Xlox" for trademark reasons).
Since you have those hard-cast bullets, you won't be able to get the proper bullet obturation with anything short of rifle-like pressures. I'm talking mid-level .30-06 pressures, .308 Win pressures, and so on. But you can do something about the bullet lube, which will help. When shooting those store-bought cast bullets, I give 'em a good coat of Liquid Alox/Xlox.
Finally, we deal with sizing. Remember what I mentioned above about getting a good gas seal? That's why we bullet casters will size our bullets specifically for our gun's chamber(s). For example, I have a Ruger Security-Six in .357M. The barrel appears to be at spec, but the chambers are a little generous. They can take bullets of 0.3595" and still pass the drop-test. Once we get to 0.3600", they need a little help chambering. Therefore, I sized my bullets to 0.3590" for that particular revolver. However, such rounds will not easily chamber, if at all, in the S&W Model 65; the largest bullets those will take is 0.3585", so I sized my bullets to 0.3580" for that gun.
But that gets a little annoying, having to have two batches of the same .38 Special load for two different revolvers. So, I take advantage of bullet obturation (my alloy is BHN 11-12) and size all of my cast "boolits" to 0.3580". Bullet obturation saves me here with the Security-Six, because the alloy is still soft enough to get squashed properly against the chamber and barrel surfaces. Gas seal occurs, and I avoid lead-fouling; Security-Six stays happy. The S&W Model 65, of course, loves it because that's very close to the max diameter that it likes anyway.
I take advantage of the same bullet obturation concept with the Ruger Super Redhawk and .45 Colt loads, especially the ".45 Colt Magnum" loads. Turns out those chambers will take 0.455" bullets, because the original spec for .45 Colt was in fact 0.454". My bullet moulds drop 'em at 0.451" to 0.452", after a little Beagling. So, they're just a little small for the chambers. Since my bullet alloy is about BHN 12, obturation gets that gas seal in place, and I avoid lead-fouling.
This was dramatically illustrated to me when first developing my first .45 Colt Magnum load. I was using BHN 15-16 alloy to cast 255gr LRNFP's. I started with 19.5 gr of 2400 and worked up. I got TERRIBLE precision on the target; it looked like a buckshot pattern at 30 yards. Lead-fouling was at epic levels. This continued until I hit 21.5gr of 2400. The leading dramatically went bye-bye, and the precision likewise dramatically tightened up. So, I went to 22.0gr of 2400. Precision on the target got even a bit tighter, and lead-fouling was GONE. Tried 22.5gr of 2400 and saw no improvement, so I stayed at 22.0gr. Remember, this is a Super Redhawk 454, so these loads are perfectly safe in this revolver. Pressure is, I estimate, in the 32,000 to 33,000 PSI neighborhood, based on the books, so right about typical .44 Magnum pressure levels. Bullet obturation here was the key. I switched to BHN 12 as an experiment, with the same 22.0gr of 2400. Same precision on target, same lack of leading. That's where my load is today.
Hopefully this info helps.