Another reloading question

[jrdudas]

OK, I got my gear and I set it up and actually loaded a round yesterday.  Set the bullet too deep because I did not adjust the die correctly.  I can see that there is a learning curve involved, but I think I will be OK.  Here's my question; I see in the loading guide (Lee book) and also on the Alliant website that the powder load for a 158 grain bullet is lower than the load for a 125 grain bullet.  This seems counter-intuitive since I would think that the heavier bullet should require a heavier charge.  I am loading .38 caliber and using a 125 grain lead bullet with Bullseye powder.  I can't find this specific combination, but I am thinking that about 3.8 grains will give me a light, but not too light round.  What do you think, and can someone explain why they call for less powder for the heavier bullet.

Thanks for your thoughts,

JR
 

[Driftwood Johnson]

Howdy

#1. Sacrifice a few bullets while you are setting up your dies the first time. Don't put powder and a primer in until you have your settings correct. Once you have your settings correct, set the dummies you made aside, you can use them to reset your dies should you change the settings for another bullet style. Don't sweat sacrificing a few bullets for this process, you are eventually going to load thousands, and it is worth the investment of a few bullets.

#2. Your question about powder charges is common. Yes, at first it seems counterintuitive. Think about it this way. For any given powder charge, the heavier the bullet, the higher the pressure generated. A heavier bullet is more resistant to moving, so the pressure builds up higher behind it before it moves. Therefore, if you use the same charge behind say a 125 grain bullet and a 158 grain bullet, and if the 125 grain charge is already at the max pressure, the heavier bullet's resistance to moving will put the pressure generated by the same charge over the maximum allowable pressure for the cartridge. It always works that way, Max pressure will always be achieved by a lower powder charge with a heavier bullet.

#3. As a brand, spanky new reloader, I strongly advise you not to start guessing about acceptable and safe powder charges. Stick with known, published data. If you cannot find the specific load you are looking for, there is probably a good reason. The specific powder may or may not be suitable for what you are trying to do. Or you may be going under the acceptable minimum load. Try looking here, I'm sure you will find what you are looking for:

http://www.alliantpowder.com/reloaders/default.aspx

[jrdudas]

Thanks for the info about the bullet weight and pressure created.  As for my particular load; I did find a Bullseye load on the Alliant link that uses a 125 grain lead bullet and calls for 4.8 grains of powder.  They say that will provide a velocity of 1024 fps.  Do I remember correctly that SASS requirements for pistol are less than 1000 fps?  What do you do in this case?

Thanks,  JR

[Shotgun Franklin]

Most reloading data gives both a maximun and minimum recommended powder charge, stay between those. Most also show the likely velocity with that charge. And you need at least 600 fps to make sure the bullet splatters rather than bounces back but under 1000 to keep from beating the targets up. Most factory handguns using .38 spl rounds are very close to point of aim with a 158 gr bullet at 800 fps. The heavier the bullet or the faster the velocity the higher the gun will tend to shoot. The lighter the bullet or the lower the velocity the lower the bullet will tend to hit. Usually....likely.

[Johnny McCrae]

Howdy Driftwood,

That is a great explanation of why heavier bullets require lighter charges. Thank you for posting this

[Whiskey Hayes]

jrdudas

I just emailed you the 2007 Alliant Reloading Manual.  It gives min and max loads.  The 2009 Allliant Manula only gives the max loads.  Look in the cowboy loading section of the 2007 Alliant manual.

Whskey Hayes

[Jefro]

Thanks for the info about the bullet weight and pressure created.  As for my particular load; I did find a Bullseye load on the Alliant link that uses a 125 grain lead bullet and calls for 4.8 grains of powder.  They say that will provide a velocity of 1024 fps.  Do I remember correctly that SASS requirements for pistol are less than 1000 fps?  What do you do in this case?

Thanks,  JR

That's gonna be a bit hot. If the manual Wiskey sends you doesn't have what your looking for, call Alliant, they will be glad to help. I called them last week for some Red Dot info, thier web site has only max for a bunch of loads, and most of them are over the SASS max.. Give them a call.

Jefro

[jrdudas]

I received the information that Whiskey Hayes sent me and it's exactly what I need. 

Thanks again,  JR

[Adirondack Jack]

On the lighter charge for a heavier bullet thing, a bit more theory.

Let's say ya start with a bullet at 100 grains and a powder charge of 5 grains half fills the case and leaves ya a "burn chamber" (space inside the case not occupied by the powder or bullet) of X size.  Ya touch it off and find it generates 7K pressure, which happily is JUST enough to get the powder to burn progressively, a clean burn that makes a nice "pop" and moves the bullet at a decent clip.  Well, in reality the bullet DOES start to move during that process, so lets say the actual burn chamber might be 1.5X, and again, happily, it all worked out.

Now ya go to a 150 grain bullet.  the heavier bullet is LONGER, and usually seats deeper in the case.  It also is heavier, resisting movement until higher pressure is created during the burn, which in turn helps the burn progress faster, generating more pressure before the bullet gets out of the way.  That bullet takes up more space, so the 5 grain charge and the bullet may leave us 1/2X space, and the heavier bullet giving us more reistance during the burn means effectively we might have .75X space, or HALF the burn chamber we had previously.  the two things together, the smaller effective burn chamber and the increased resistance MIGHT make for pressures as much as THREE TIMES what we had before.

So, looking at our data we find a proper charge might be 3.5 grains for the heavier bullet, giving us a larger initial burn chamber (leftover space inside the case) and a somewhat arger effective burn chamber as the heavy slug doesn't move out of the way as fast with a lighter charge.  Further, since there is less powder, the powder charge may get consumed fully before the bullet gets out of the way, lowering the peak pressure AND gas volume, so maybe we end up back to the original 7K pressures, and a nice "pop" at target load levels like we had before.....

Heavier, longer, harder (yes, jacketed or hard lead makes more pressure than soft lead)or deeper seated bullet INCREASES pressures.  Lighter, shorter softer, or longer seated bullet lowers pressures.  Powder charges have to be adjusted accordingly.  THAT is why we have load books, and can't simply guess.  Use em.

FWIW:  Even ole Elmer Keith said "Wandering beyond the books is a business for the man who fully knows what he is about".  He knew what he was talking about, having blown up guns and hurt himself in the process of learning.

[Frenchie]

Lee "Modern Reloading 2nd Edition" Reloading Manual is the most comprehensive reloading book I've found yet. $13.99 at MidwayUSA, $30.00 everywhere else. It explains the mysteries of pressure so even I can understand it. I also highly recommend Hatcher's Notebook by Julian Hatcher for firearms history and just plain great reading.