Just got some new brass cases in 300win mag. Have 2 boxes obviously different batches going by packaging and headstamp. Both made by same manufacturer...

Weighed a couple of cases from each box.. 1 box was around 215gr for 1 case,, other box was around the 260gr mark...

Are at odds as to such a difference in weight???? Have checked scales and they appear to be accurate with projectiles of known weight......

Weight is quite informative if: all is of the same brand, clean, it's been once fired so all have the same external dimensions, then anally prepped with length trim, primer pocket work, and neck turning/reaming.

If all external dimensions are equal, then disparities in weight are indicative of more or less material on the inside. Some say it's not worth the bother with sporting arms. In my book, any aspect of the sport that generates a consistent product certainly cannot hurt.

I once prepped and sorted 400+ 22-250 cartridges down to the most consistent 100. Went from about a 1 moa unit down to about half that.

If you would make it known we may be able to better fill you in.

21% difference in case weight is a huge disparity for commercial brass from the same manufacturer. The biggest I've ever heard of.

Some "manufacturers" aren't manufacturers.

Nosler 308 Winchester stuff has changed weight quite a bit over time. Now that Nosler is starting to make their own yet another change may be taking place.

Several of the "normal" OEMs of brass are farming out production to other OEM's or third party metal forming houses. Just heard of a new company coming out marketing brass and release said that they have been supplying OEM's for years. If the headstamps are different, they came off different machines, likely from different manufacturers. You are going to need significantly different loads for the two lots. I would send one lot back or sell it. No way that would conform to normal QC standards.

How would you know which lot to send back, that the next lot you buy to replace it would match?

Keep it separate and use it.

Too easy for me to mix brass so the heavy lot goes back or down the road. Personally, if I were the OP, I wouldn't be buying any more brass from that company and it would probably be a good public service to state the vendor. That significant of a difference in internal volume is likely going to cause overpressure even with starting loads. Unless of course the light ones have significantly more volume than average.....in either case it is f'ed up and shouldn't be on the market.

I agree please post your sources of brass purchases so we can all benefit. I feel no one wants to experience at best inconsistent poor accuracy or worse. Let the market determine the future.
ABLE

Norma actually publishes data for this anomaly for the 300wm. Their weights are 270 and 215 about spot on for your data. This has been an issue for a while you will probably not see a difference in velocity for either case weight the capacity is less in the heavier and vis-à-vis pressure is greater. Max loads of course differ by about 3.5 gr.

Good luck and shoot straight.

Bob