Different brand brass cause velocity and group issues?

[huntoregon]

I had a load for my 300 win mag with 78.5 grains of H-1000 in Federal brass that shot great. I loaded the same powder in Winchester brass and it didn't shoot as good and velocity was down about 90 fps. So I upped the load to 80 grains and velocity came back to where it was but the groups still not quite as good.

Is this normal?

 

[FearNoWind]

"Normal"? Can't say,
"Unusual"? - Not entirely.
It is rare to find case capacity or case/neck wall thickness to be identical from one manufacturers brass to another. "Upping" the load to obtain comparable muzzle velocity without some very careful consideration can dramatically increase the risk of excessive pressures however so be careful to rely on a quality reloading manual's recommendations before going down that road.
When I have to change the type of brass I'm using I always start at square one and work up an entirely new load for that brass. Otherwise I mighty be trying to fit two horses into a one horse trailer.

 

[MagnumManiac]

I had a load for my 300 win mag with 78.5 grains of H-1000 in Federal brass that shot great. I loaded the same powder in Winchester brass and it didn't shoot as good and velocity was down about 90 fps. So I upped the load to 80 grains and velocity came back to where it was but the groups still not quite as good.

Is this normal?

This is completely normal.
Differing brands of brass and case capacity will change internal powder burn rates.
Also, matching the velocity may or may not, in this case not, result in another node.
This is why you ALWAYS work up when you change ANYTHING.
I did away with using quickload many moons ago cuz it would predict nodes at velocities that just didn't happen in real life. No 2 barrels will oscillate the same, this is why groups change when you switch brass.
You may find you have to change COAL to find the sweet spot again.

Cheers.
gun)

 

[J E Custom]

Both responses were spot on. I have seen even the same brand of brass change the POI or the velocity because of the different number of firings from one batch to another.

Now I shoot all the brass I have for that cartridge, before I re load for it. and when it needs annealing I do all and prep them for the next loading. this helps maintain accuracy and dependability of the brass.

I normally do batches of 2 or 300 depending how much I use the rifle and never mix the brass batches. I keep each batch in sealed containers with the caliber, and number of firings clearly marked on the container.

If you change anything it is always best to start over with load testing in my opinion.

J E CUSTOM

 

[dsculley]

These little tidbits is why I like to read these threads. I know that different brands of brass can (usually do) have different capacities and usually require work up as with a new load. I had not thought about keeping my brass for a particular gun/load "in sync" the way J E Custom described. It makes sense and is something I can easily incorporate in my procedures in the future. Thank you for the tip.

 

[Corey Schwanz]

Yes, brass thickness can vary causing internal volume differences which lead to pressure and speed variation.

General rule of thumb is you will want to at least check and probably re-work a load slightly when you change ANY component in the process. New bullets and powders are normal, but brass will often get overlooked.

 

[Frank in the Laurels]

There's no uniform rule followed by brass makers, that's for sure ! One types can be extremely different from another which cause big differences on the amount of powder and air that can fit..both of which can effect and affect those things you mentioned, pressure and velocity...the amazing thing is that sometimes there's even a difference from a single company, that always amazes me but it's not uncommon. If your someone who shoots right on the edge it matters, a grain or two down and it's not bad no matter what...

 

[Trnelson]

I usually weight sort all of my brass for each rifle. In a magnum case like the 300 win mag you can probably get away with +/- 4g without seeing much on terms of velocity and accuracy. In .30/06 I've seen remington cases as light as 179g and military surplus brass as heavy as 208g. You can readily see that there's going to be an issue if one is attempting to treat them all alike. Pressure = force / area
Less area and equal force will yield more pressure which directly correlates to an increase in velocity, provided it happens in the barrel.