View Full Version : Is there a hardness vs velocity chart I can use?
January 26, 2010, 07:54 PM
I heat treated some of my 175gr tumble lube 10mm bullets using the oven quench method, so according to this article (http://www.surplusrifle.com/shooting/alloyhardness/index.asp) they should have a BHN of around 35. I shot some clocking around 1050 fps and got pretty severe leading. It was so bad I had to cut a square of lead away cloth to push down the barrel. I'm guessing leading means I have to drive the bullet slower. I know if you tune the hardness to velocity ratio you can virtually eliminate leading, so is there some chart to help me with this?
BHN 0-10 Keep velocity to x-y fps
BHN 10-20 Keep velocity to y-z fps
January 26, 2010, 08:07 PM
Well, it is not always that simple. Bullet FIT should be your #1 concern. Start by slugging your barrel to see what your groove diameter is. If you are not sure what I mean by this, you can probably find a video on youtube...or let me know and I can explain. Bullet fit is paramount. Ideally, you want your bullet to be 1-2 thousandths over groove diameter. The bullet needs to be bigger to help seal the gas from pushing around the bullet (and causing gas cutting and leading). 1050 FPS...no need to harden your alloy. If you are using WWs, just air cool them. Harder is not always better. A softer alloy will obturate your bore much more easily. Good luck!
357 Mag - 158 grn RFN air cooled 1200 FPS - no leading.......155 grn SWC gas checked (copper cup that goes on the base of the bullet...certain molds are gas check designs so you cant use a gas check on just any bullet) air cooled 1375 FPS - no leading. My groove diameter is .357 and I size my bullets at .358.
January 26, 2010, 11:42 PM
+1 on bullet fit. Here's a PSI chart I use. Velocity and psi go hand in hand. If your reloading manual lists psi for lead bullets it's a fairly good guide. Lyman manuals list CUP and PSI, yes they're different. The Modern Reloading 2nd Edition by Lee is also a good reference. I use the chart as a guide more than the rule but so far it's been good for my loads.
January 27, 2010, 05:11 PM
OK, I slugged the barrel and got 0.399 to 0.400 inches, depending on how hard I close the caliper. I size my bullets to 0.401, so that should be fine. According to the chart posted I'm also OK in terms of hardness since the PSI listed for my load is 32,500. I guess I'll try just letting them air harden and see how that goes. Thanks for the help.
January 27, 2010, 06:46 PM
How are you sizing them? Have you checked your sizer die? Just because it is stamped ".401" on the die does not necesarily mean it was manufactured to spec. I think that air cooling them will help. Also, can you tell us if the leading was the entire length of the barrel, at the chamber end, or at the muzzle end? This can give us clues to figure out your leading problem.
January 27, 2010, 06:55 PM
I'm using a Lee sizer as shown here (http://www.leeprecision.com/html/catalog/lubesize.html). The sizer die is accurate, I measured the sized bullets and they were .401. They were also re-lubed after sizing as per Lee instructions. The leading is the entire length of the barrel.
January 27, 2010, 07:48 PM
So you are using Lee Liquid Alox? I assume this is true. When you cast your bullets, what is their "as cast diameter"...(diameter before sizing). Also, is this a tumble lube style bullet? Some people have great luck with LLA and some don't. Some people add ingredients to LLA to make it "better". One other thing to check is to make sure your barrel is squeaky clean befor shooting your next loads. Any crap left in the barrel, whether it is previous copper foulings or lead, can cause leading. We'll figure it out!
January 27, 2010, 10:01 PM
Is there shiney spots or parts of the bullet shiney after sizing ????
If not your bullets are droppin under sized to begin with!!
Try lubbin & shootin with out sizing em if they`ll chamber.
Do you use a factory crimp die??? if so leave the FCD step off & turn the flare in just a smell with the roll crimper.
To answer your ?? lee has a psi to bhn scale
January 28, 2010, 03:26 PM
Yes, I am using liquid alox with the tumble lube bullets. I tried both 100% alox and cutting it with mineral spirits, but got the same amount of leading. I just cast a few more, so here it is:
The as cast diameter measured at the top is 0.401 to 0.402, measured at the base is 0.400 to 0.401, with a few at 0.399. I see this might be a problem. Does the whole bullet need to be 0.001 above bore diameter, or just part of the bullet? I let these air cool. Perhaps I should try shooting them as cast without resizing? I do use the Lee factory crimp die, since the KKM barrel I shoot them in is very tight. Could this make them too small?
I'm using wheel weights with about 3 feet of 60% lead 40% tin solder per 10lb pot to help the mold fill out better. Without the tin I the top edge above the lube bands got really rounded and caused chambering problems. Would too much tin make the bullets shrink smaller when they cool?
January 28, 2010, 06:40 PM
The bullet needs to be .001 over groove diameter. The undersized bullet could be your problem. Here is what I would try. Shoot them as cast and, like GPMAN said, use the roll crimper to just take the flare out of the case mouth. Sometimes, the carbide sizer rings will actually squeeze the brass and inadvertantly "resize" your bullet. BUT, you must check to make sure they will still chamber in your particular gun, To do this, take your gun apart and drop the loaded rounds in your barrel. If they fall in, and come back out with ease, then you can shoot them.
To answer your other question about the tin making the bullet smaller. No, tin helps improve fillout and just BARELY hardens your alloy...not much to even worry about. So, try loading some unsized and see if they will chamber. If they chamber, give them a shot and see what happens.
Now, if you still get leading, there is a way to "open up" the mold so it drops slightly larger bullets...which is what may need to be done. We will try that if the next solution fails. Let us know how it goes.
BTW, when loading up your next batch, start with the starting load and work up to the max load. I would do 1 or 2 laods in between min and max for a total of 3 or 4 different loads at different charge weights. The reason: I have had loads lead my barely terribly...but when pushed a little harder, they did not lead at all. Someimes, the higher pressure is need to seal the bore. But, be sure to clean thoroughly after test firing each load. Good luck!
January 29, 2010, 12:53 AM
Just another thought on the bullet size. I use the TL bullets also just not for a .40. I find I have to keep my lead temp. around 750 to 800 to get good fill out with the lee molds. I usually give a 6 count before I can watch the sprue freeze.
February 11, 2010, 06:25 PM
I saw your post about shooting really hard bullets, 35 BHN. I have never been able to get bullets up to 35 BHN. When I oven treat bullets about the hardest I have ever gotten them is about 32 BHN using Veral Smith's BHN tester.
Your problem sounds as though you have a problem with bullet fit, not hardness. Why shoot bullets that hard anyway? Start with the lowest suggested load, not the max load. Check out Norm Johnson and C.E. 'Ed' Harris suggestions over at the Cast Bullet Association site. They have a lot of good suggestions and tips.
I've been shooting cast bullets since 1958, and I have not had many problems with leading. Watch out using fillers, you can put a ring in your barrel very quickly. It only costs a few $100 bucks to replace a barrel! It has happened to me twice. I do not use any fillers at all any more.
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