Interpolating load data

[chris623]

I shoot only cast bullets.  I've got Lyman's books but even there, I have a problem finding loads for the bullet I cast and the powders I have.  How can I learn to safely substitute?  For example, can I safely substitute a 170 gr LSWC in a published load for the same weight as a jacketed bullet?  If my 170 gr bullet is shown, but with a powder I don't have, how can I substitute one I do?  I know I can use .38 Special data for .357 cases.........if I want reduced loads........and, of course, know not to load .357 loads in .38 Spl cases.  But what can I safely substitute and is there some sort of book that will tell me what I can and can't change?

[cherokeetracker]

 want to know how to develop loads Correct?
Answer me this before I start trying to help so I know I am on the same page.

Charles

[aus71383]

I've interpolated some data before - looking at similar bullet weights for a cast bullet, comparing to other load data for bullet weights close to the same but above and below, and coming up with a starting load in between. Is this what you're talking about? If so, I'd say the answer is "more actual data". What reloading manuals do you have besides Lyman? In general, cast bullets create lower pressures than jacketed. But - it pays to be thorough....and cautious. Too low of a starting load can be a problem too. Be careful!

edited to add:    it's also very important to look at the volume of the bullet that sits in the case when comparing bullets/load data

[COR]

I'll address your question regarding the bullets of like weight. If you are using jacketed date for lead bullets of same weight you are fine...however using lead data for jacketed could cause some issues with warmer loads due to increased pressure of the jacketed bullet.

Many of the powder companies have online data available...I'd start there.

[chris623]

It looks as if I'm not expressing myself correctly. (which often happens when I don't know what I'm talking about.) 

I have a shelf full of different powders.  I only have a couple of bullets I use for my .357 Blackhawk.  Would like to try different loads, but don't find them in any of the books.  I guess basically, my first question should simply have been..........can I substitute a lead bullet of the same weight of a jacketed bullet in the load data?  As I mentioned, I'm not talking hot loads, just target loads.  The second question was about trying to find out how to safely figure out a load "between .38 Special and .357 magnum because I use the larger .357 case.............so, obviously, there are no published loads to go by.  What I'm not understanding is the change (drop, I'd assume) in pressure that I'm creating when I use the .38 Special data in .357 cases.  Needless to say it's hard to ask a question about something I don't understand.

Hope all that is clear enough.

EDIT:  And, yes, cherokeetracker, I'm trying to learn how to develop loads when none are published.

[webber]

"edited to add: it's also very important to look at the volume of the bullet that sits in the case when comparing bullets/load data"

Exactly right even if the bullets are similar in weight. Anyone that doesn't mention that in person or writing on the Internet don't listen to them. Especially with handgun ammo and its small capacity and fast powders.
Even most magnum handgun ammo is small capacity compared to magnum rifle cartridges and even slow pistol powders are fast compared to fast rifle powders.
Keep this in mind regardless what the "Experts" say.

[aus71383]

Chances are good that the loads you are looking for are already published. There is a a multitude of data for .38 and .357. What powders do you have on your shelf? and what bullets are you hoping to use?

[chris623]

Pretty long list of powder. Charles and I have been going back and forth through PM's and he's making some suggestions.

[jsh]

I will throw my .02 in here if I understand the question correctly.
#1You are wanting a load in a 357 case, hotter than a 38 special yet below a 357?
#2You are wondering about using jacketed data for cast bullets of similar or equal weights?

#1 sounds like a 38+P load to me? I would start off with a starting load for 357, or a 38+P load in 357 brass. How ever use a lot of caution when fooling with 296/H110, which I myself would not use in the is circumstance. Unique will get you what you seek I believe.

#2 this one can and does get a "iffy". Today there are so many designs of bullets with the same number designation. Or, you see the term Keith type or LBT, both used very loosely, which chaps me because I have a fair bit of respect for both individuals. As mentioned above it is how much case space the projectile will take up, not necessarily a particular design number. What I am getting at is you can cast your own, purchase several others with all the same designation. Yet when compared they are different in weight,design,crimp groove location,nose length etc. This is where as a hand loader it is YOUR responsibility to read and research for your own wants and needs, safely.
Ammo,powder,primer and brass is cheap. Guns are expensive and hospital bills are even more.
I have used with good success in some circumstances jacketed data with cast bullets.
Size is king in my book. Proper fitting CB's go a long way before alloy and lube come into play imho.

[Deleted]

What sort of velocities are you looking for, and which bullet you want to use? If you're wanting to use the 170 gr bullet you mentioned in your original post, the only real limiting factor is that we don't know what velocities you are looking for. For example, the Keith design bullet has bounced around in weight from 173 gr, 170, and 169, all from the same mould manufacturer (Lyman). Gas check designs will generate higher chamber pressures than plain based bullets. There is a lot of data available for the Keith bullet in both 38 & 357 magnum loads. Elmers grouse load for 38 spl with his bullet as originally designed at 173 gr used Bullseye. FWIW, the 358429 was originally designed as a 38 Spl bullet anyway. It predated the 357 mag caliber by a number of years. If this is your situation, Lyman manuals show a number of starting loads with 358429, using faster burning powders in both 38 & .357 loads.

[AxeHandle]

Way to many variables to step out on a limb here for me. There are so many loading manuals out there. Big companies have web sites with extensive loading data too. My recommendation is that you get your hands on as many loading data sources as possible. Develop your own feel for what to do and what not to do. You will see people write about off the wall stuff they load. Stay away from loads that are significantly heavier, lighter, or completely outside the numbers you see published.