IMR4166 question

sprink · May 2, 2015

Hodgdon site says max load for .308 with 175gr bullet is 43.1gr. Max load for 180gr .308 bullet is 45.1gr. I'm loading 178gr Amax and was curious what max I should use. I know I need to work up to the max but since the 178gr Amax kind of falls in between the two.

Darkker · May 3, 2015

You should never "use" any max number published in a book, they didn't test with your rifles specs; so the results will not be the same.
Published data has SAAMI minimum spec chamber and bore/grooved barrels. Yours will have larger dimensions, so if you are matching published velocities; your pressures are higher.

Better yet, just start low and stop when you find a node. No one cares how fast your load is when you can't hit the broad side of a barn.

Benchrest · May 3, 2015

QuickLOAD has lots to say about "max" (generalization) loads, most of it negative (in terms of SAAMI guidelines).

I'm in the habit of checking book loads against the computer (I get it, it's only a model), and while some are below or at SAMMI max average, many aren't.

Caused Sierra to raise an eyebrow.

Steve M · May 4, 2015

Ordinarily I'd say use the Speer 180gr data, but in this case I'd probably use the lesser Sierra 175gr data until I could get my hands on a Hornady reloading manual.

Darkker · May 4, 2015

QuickLoad is an interesting little toy. Sadly, as they say "garbage in, garbage out". Hartmut gets anything he wants from the euros, and thus far the Pressure Trace shows that his info appears to be close. The trouble is when using anything that Hodgdon resells. Hodgy won't give you any practical info on anything they sell, such as nominal burning rate variation or BD numbers. I suspect because they don't manufacture anything. In any rate not having any info on sample size, nor era produced; means Hartmut's days can be sadly limited. While he does some limited bomb testing, that only gives a generalized burning rate curve. Case used in, will greatly change that.