Home Forums Hunting & Shooting Ask The Gunwriters Load data discrepancies

Comparing the Sierra to the Hornady loading manuals for data on Varget and 150 grain bullets in my .308.
Sierra lists 47 grains of Varget with 150 Sierra SP as maximum, while Hornady lists 45 grains of Varget as maximum for its 150 grain corelocked bullets.
Is the 150 grain corelocked Hornady that much harder a bullet then the 150 Sierra SP?
It’s a nuisance, got to ladder test all over again, since my Sierra bullets I used before are not available in Calgary at the moment.

I know there are variations in powder lot numbers, test barrels etc, but I thought 2 full grains difference is a lot, correct me if I am wrong.

I have seen similar differences in loads over the years and that is one reason that I have about a dozen different load manuals.

I have no explanation or further comment.

Speer 46.5
Nosler 47C
Sierra 47.4C
Hodgdon 47C

I never have trusted Hornady data since 94 since they never match with even the powder manufacturers.

What brass are you using?

Hornady brass, sorted by weight.

Bullets vary, every barrel is different and powder lots may vary so I'm not surprised when max loads from the manuals don't line up.

I've had fast barrels that showed pressure/speed quickly and some barrels that I could load over "book max" before I ever approached published velocities.

That's why they all say to work up from starting loads to see where your rifle needs to be.

Everything is different, the brass, primer, powder lot #, bullet, rifle, etc., so results will be different as well.

Re-read what Colodog wrote above.

The man with two watches never knows what time it is.

47 gr is closer to the pressure I would want to run [slightly less crazy wimpy], but fitting more than 45 gr may be hard to do.

I just put 47 grains of Varget into a new, unfired Hornady 308 Win. match case. I poured it swirl style through a powder funnel and did not use a drop tube. The powder came right to the base of the neck so if pressures in the OP's rifle allow then the volume of fill shouldn't be a problem.

Yeah, you're wrong.

Ten years I published my book RIFLE TROUBLE-SHOOTING AND HANDLOADING (which is still selling pretty well), and included a fairly long chapter titled "Reloading Data," which explains all the reasons data varies so much from source to source. Though I did also point out that these days it tends to vary less than it used to, due to more standardized pressure-testing.

Yet magazine readers and Campfire members kept asking the same question about variations, so when I published the much larger BIG BOOK OF GUN GACK in 2015, I included the same chapter, this time called it "Why Reloading Data Varies."

My advice is the get over it.

i've kind of always figured published max laod data is likely well under any true "max" data simply becasue this country has far more lawyers in it than necessary I start in the mid range and work up from there

Lawyers have relatively little to do with it--and there's also the question of what's "true max."

Maximum load data is pretty much determined by SAAMI, which determines it after considering what firearms have been produced in any chambering, plus how much pressures tend to vary (both high AND low) in a particular cartridge.

But no matter what the rifle round, SAAMI never allows an average maximum pressure (MAP) of 65,000 PSI. This is because their standardized testing takes place at 70 degrees Fahrenheit, and even today many powders will result in FAR higher pressures when a rifle's shot in warmer conditions. So they prefer some margin of safety to allow for that factor--or a worn barrel, which contrary to popular believe can actually result in higher pressures, especially during earlier stages of erosion.