How Do I Figure a Starting Load?

[R.Ph. 380]

OK, I've filled a military 308 case with Varget Powder and the powder weighed 49.5 grn. I then filled an exactly same case length 308 Winchester civilian case and the powder weighed 54.3 grn. That's a difference of 4.8grns. Now, that differential will hold true for only Varget or should I subtract the percentage from the published powder weights of any round. I'm loading 44 grns of Varget in Winchester brass, 150 grn BTSP with CCI LRP. Will that translate to 40.305 grn in my LC military brass I was just gifted with? Is the volume vs weight vs pressure a linear equation? If not, where do I start to work up a load? Pick an arbitrary point?

My question, will the percentage differential or 91.1602% hold true for other powders or do I have to recalculate for each powder? Will it give me the weight of other powders or just a general idea of where to start?

Bill
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[mountainman]

personally, I will only go by a reloading manual only. Doesn't matter what brand of brass I use, I'll start low and work my way up looking for pressure signs. Hornady says a 308 ,150gr. using Varget, starting load is 35.9 grs with a max load at 44.9 grs. I would start at 37.0 grs and work my way up to be on the safe side and let pressure signs tell what to do. This is the only answer I have for you other then, I wouldn't use a load other then one I looked up. Nothing from the Internet or other people.

 

[rscott5028]

Amen! Good advice Mountainman.

It's great to hear about all the loads and velocities that people tell about on the Internet.

But, I only go by the published data from major manufacturers by starting low and working up.

And, keep your manuals up to date. Powders and data do change over time.

-- richard

 

[BigSkyGP]

For a while I used a 20 some year old speer manual for all my load data, 'till a friend of mine blew up his M1A.

Use the most current data from the powder manufacture. Most of them have web sites where data is updated fairly often. I go with that, especially when I get into a new lot of powder. You end up re-evaluating your load, goes with reloading.

Yes, your LC brass will have different pressure curves, don't worry about the gift part, it's fine brass. Think of it this way, you will gain some performance, and burn less powder to do it. Work up the load for the brass in your rifle.

 

[RDM416]

R.PH 380,

+1 to what the previous posts are telling you. Until you gain many years of experience you should never deviate from a loading manual or official data from a manufacturer website. Most powder and bullet companies have data available and will provide you with more if you call them.

There is a real reason for all the minimum and maximum loads listed in the manuals. For example your military brass is typically thicker (that is why you are seeing less volume) than civilian brass. Because there is less volume the pressures will be higher. It is possible to have a load that works just fine with civilian brass but would be dangerously over pressure in the military LC brass. That is the reason for the "start at the minimum load and work up to no more than max" warning. And remember "max" load is exactly that. Different rifles will behave differently as well. Some actions are stronger than others, etc. If you plan to use the same load in different rifles make sure you use them all during your work-up process, or just keep the load toward the low to middle of the scale.

Handloaders who are working with wildcats may not always have exact loading data available since they are not dealing with factory rounds. In that case they may have to rely on starting data from the one who developed the wildcat or from those who are using it. At some point some may develop the knowledge to work up loads from scratch..... based on powder burn rates, bullet weight, bearing surface.......... Until you have been loading for many many years, just stick to standard published data.

 

[boomtube]

"Is the volume vs weight vs pressure a linear equation? "

No.

Use your manual and work up your charges normally, no starting load will blow your gun up. You will likely see excess pressure signs before reaching book max but that's what starting low and working up is all about.