Powder reduction

[Finney]

I have been loading 308WIN for years using Winchester brass. I have recently acquired a lot of Federal and Lake City brass. The Winchester weight averages 160.5gr and the Federal and Lake City averages 181.4gr.
I have been using 44gr of Varget for 168gr bullets.
How much do I need to reduce the powder when switching to the Federal or lake city brass?

 

[jds holler]

I think I'd decrease by 10%, and work from there. I'm interested to hear what others think. jd

 

[JeffG818]

10% powder reduction is a good idea, till you know what you are dealing with.

 

[Finney]

Thanks

 

[jimbires]

I would check water capacity on these different cases . that would tell you more than case weight . the cases would need to be fired in your gun , and not resized .

 

[spclark]

As Winchester brass is noted for its rather generous capacity, 10% reduction is a worthwhile suggestion. My own experience (with different powder, different brass and lighter bullets) suggests something closer to 5% to be a reasonable starting place so your 44.0 grains would be reduced to 41.8 grains.

Safety first, last and always though so take appropriate steps to ensure both your safety and those you may be shooting alongside.

 

[riflewoman]

The years old rule of thumb was 2 grains of powder in the IMR 4895 / 4064 speeds between LC and Commercial cases. This was to get the same velocity/ zeros. So drop it 3 and work up in .5 grain increments over a chronograph.

 

[dstoenner]

I shot 42 gn of varget behind 168 SMK in LC brass. Never over pressure. I sort of thought it was middle of the road. This was in a 700 and an M1 Garand

David