Different Starting Loads?

[Josh Smith]

Hello,

I start my handloads using, of course, the minimum load.

I'm aware that below minimum can cause pressure spikes.

My question is this: Different sources list different starting loads. For example, I like Varget. When loading for the 7,9x57J, I go first to Hodgdon Powders' data. They list, for a Hornady 150grn soft point bullet, a starting load of 45.5grns for a velocity of 2561fps and a pressure of 37.5K CUP.

Now, I flip over to Sierra and their load data says 45.1grns to start. Granted, different bullet with different bearing surface, but it also has a longer COL. Same weight bullet though.

Now, I go to Hornady's load data and they list a starting load of 43.5grns for a 2400ish feet-per-second. I like that -- but why the 2 grain discrepancy between the powder and bullet manufacturer?

I tend to think the powder people know their pressures and such the best so I go with their data before the bullet peoples' data, but it still leads to some confusion.

On top of everything else, my bullet is this:

http://www.buffaloarms.com/Detail.aspx?PROD=158303&CAT=4178

It's made by Buffalo Arms Corporation and appears to have about the same bearing surface as the Hornady, so I load and watch for pressure sign.

Is this the correct procedure?

Should I be doing anything differently? How does one go about getting data for bullets not listed?

Any other advice?

Thanks,

Josh

[XDRoX]

Going below starting loads is fine. As you go lower, first the gun will not cycle (if it's an auto). Continue to go lower and eventually you'll get a squib. The theoretical Pressure spikes happen when hardly any powder at all is used. Like 5gr instead of 45gr. And, I've never seen this phenomenon happen in real life.

As for finding data you your actual components, it's hard to do. But you'll get better at it with time. For now, just use data with the same bullet weight as yours and you'll be fine. OAL isn't that important as long as you're not compressing the powder. Longer is better as long as it functions in your gun, so load them as long as possible.

Hope this helps.

[Bill Steele]

Spot on.

Going below starting loads is fine. As you go lower, first the gun will not cycle (if it's an auto). Continue to go lower and eventually you'll get a squib. The theoretical Pressure spikes happen when hardly any powder at all is used. Like 5gr instead of 45gr. And, I've never seen this phenomenon happen in real life.

As for finding data you your actual components, it's hard to do. But you'll get better at it with time. For now, just use data with the same bullet weight as yours and you'll be fine. OAL isn't that important as long as you're not compressing the powder. Longer is better as long as it functions in your gun, so load them as long as possible.

Hope this helps.

I agree.

There is a lot of misinformation about the risks of loading below start levels, sometimes from otherwise very reliable sources.

Richard Lee in his 2E loading guide goes into a lot of detail about downloading well below socalled "minimums" or start levels. It is a good read, he also includes a lot of actual data on a few of the popular rifle calibers and using various powders (like .308, .30-06, .30-30) loaded down as low 50% below start levels. He also provides some "rules of thumb" guidelines when considering downloading even the slowest powders like BMG.

[Fyathyrio]

Another thing to factor in is what equipment did the source use to get their data? If they test fired from a universal receiver with a 24" barrel it may not relate to your equipment as well as another manufacturer that used an actual weapon similar to yours.