Different Max Powder loads

[Gardien]

New to relaoding and beginning to work up my first series of .308 loads with IMR 4064 and 165 gr SGK (SBT).

Can someone help me upderstand why the Sierra manual lists the max 4064 load at 43.5 gr and the Speer manual lists 45.0 for a 165 gr SBT?

The minimum loads are also different at 41.0 gr for Speer and 37.6 gr for Sierra.

I just trying to get and idea of the range I should be working in to optimize the load for my rifle.

Thanks in advance.

 

[freelunch]

The printed Hodgdon Reloading Manual using IMR4064 has 42.0gr, 2554 fps, 43,800psi for a start level; and max load at 46.3gr compressed, 2767 fps, 59,700 psi for max load. This is with a COAL of 2.750" for Hornady 165gr SP, 24" barrel and Federal 210M primers.

I would use Hodgdon's information as the guideline if you have a newer rifle. If you have an old rifle that cannot use modern SAAMI load levels of max 60,191 psi chamber pressure, then go with the lower level from Sierra. The 43.5gr may/likely be an accuracy node load. You can use Hodgdon's Reloading information online here.

http://data.hodgdon.com/main_menu.asp

 

[Gardien]

Thanks, Freelunch. My rifle is brand new with 30 rounds down it so far. I'll take a look at Hogdon.

Just visited their web site...very impressive.

 

[Russ Hatch]

The bullets are different. They offer different resistance to being engraved by the rifling because of different bearing surfaces and materials. When I change bullet brands I reduce the load 10% and work back up, or use the manual for that brand of bullet. Each rifle is different and the manual's loads are what the manufacturer has found to be safe with their bullet and that lot of powder. Confused enough now? Just follow the recommended loads and watch for pressure signs and you'll be ok.
Russ

 

[Gardien]

Thanks, Russ. Yes, it does make sense. Since I'm using Sierra, I'll start with their recommendations.

I guess I'm overanalyzing this before I start.

 

[boomtube]

The rifles used to develop the data were different.

Different bullets, etc, pale in significence beside that.