Hornady data vs. Speer & Hodgdon

[Gary D]

OK a Question to the more experienced out there. is the difference of 0.001" bullet diameter that significant?

The load data in the Hornady manual reads like this:
.303 174 gn RN, Dia. 0.312"
IMR 4350...............Min. 37.0gn Max 44.6gn
Varget..................Min 31.6gn Max 39.1gn

when compared to other manuals using 174gn .311"Dia bullets I get this

Speer manual
.303 174gn RN, Dia .311

IMR 4350...................min 43.0 max 47.0C
Varget......................min 37.0 max 41.0

Hodgdon data
.303 174gn Sierra, dia.311

H 4350*...................min 43.0 max 48.0C
Varget.....................min 38.0 max 42.0

(* yes it is H4350 not IMR4350, although I understand they are nearly identical, that's why I have included the Varget data as well)

as you can see the Hornady data tops out where the Speer and Hodgdon data begins. Should I load the HDY bullets to their manual specs or is their data bent and load as I would other .311dia 174gn loads (my usual loads are 40.5 gn Varget or 46.0gn IMR 4350 Both well above the HDY data).

 

[Gary D]

BTW, the Hornady and Hodgdon (and Speer) manuals also differ on other weight bullets, but most notably the Hodgdon data and the HDY data using the SAME HDY bullet read...

HDY manual
.303 HDY 150gn SP .312dia
IMR4895................................min 29.9 max 38.9
varget.......................................33.0.........40.8

Hodgdon data
.303 HDY 150gn SP .312dia
IMR4895...............................Min 36.0 max 40.0
varget.......................................39.0........43.0

*Speer manual FWIW
.303 150gn SP .311dia
IMR4895....................................40.0..........44.0
Varget.......................................41.0.........45.0

What should I make of this???? is the Hornady manual too conservative on their .303 data?

 

[B]

I had a similar problem with Accurate's data and Hornady for the same bullet weight. Hornady turned out to be much more accurate than Accurate. Hornady listed a max charge of 13.2 grains compared to Accurate's 12.5! Both supposedly achieve the same pressure and velocity.

 

[sunray]

Hornady and Speer data is for their bullets only. Hodgdon's data is for the powder with various bullet makes. Either way, load for the bullet weight. Who made it doesn't matter.
"...understand they are nearly identical..." Yep. Number's 91 and 92 on the burn rate chart. Same thing. I suspect Hodgdon keeps the IMR brand name just because of brand loyalty of some shooters.

 

[Gary D]

Sunray, I guess I was more concerned with the .312 Dia of the Hornady if it could honestly account for that much difference compared to a .311 in a tight barrel. Or is this just Hornady being over cautious about old milsurp guns and the legal liability with their published data.

With a .312 dia bullet it would appear they are catering to more heavily worn rifles.

 

[John Y Cannuck]

Sunray, I guess I was more concerned with the .312 Dia of the Hornady if it could honestly account for that much difference compared to a .311 in a tight barrel.

There are far too many variables to say something like that with any hope of accuracy. Every rifle is different, especially so when talking about military rifles that have been built in many plants, in many countries around the world.
More than just bore diameters, fits and tolerances vary widely.

Now if you fired the .311, and the .312, in the same barrel, with the same case, same primer, same exact load, the 312 should give you more pressure. Provided of course that the bullet construction was exactly the same, by means of materials, the weight, and the bore riding length was equal.

 

[Gary D]

You're right, I guess the best bet is to go build a few more rounds based on the Hornady data up to my normal load (approx 1.5gn over Hornady data) and go shoot them and watch for pressure signs. I'll post my findings when I get back on Tuesday or Wednesday.