Morn'in reloaders.
I have posted a number of times both on this forum and others, the need for keeping brass separated by Brand, times fired, AND ---------- LOT NUMBER.
Using a situation which happened to me with Remington brass, back a number of years, as an example.
The result of using some odd lot number brass, being some very high pressures!!!!!!!!!!!!!!
Some time back, a friend gave me three boxes of new and unfired, Winchester .243 brass and 2 1/2 boxes of Winchester .270 brass in the same condition.
This brass has been around for awhile, as the boxes of .243 brass are marked, $2.40 ea. and the .270 - $2.52 ea.
In both cases, there were 2 boxes with the same lot # and a third with a different lot#. In the case of the .270, the box with the odd lot number contained only 10 new cases.
I weighed all the brass, averaged the wts., and yes there is a difference. PROBABLY NOT ENOUGH IN THIS CASE TO CAUSE SAFETY CONCERNS, BUT FOR SURE ENOUGH TO FOUL UP YOUR GROUPS AT THE VERY LEAST!
On the .243, Lot #69RH3 averaged, 163.44gr. (20 cases) with the high being 165.2 and the low 160.6.
With lot # 79YE22, the average was 165.865gr. (40 cases) with the high of 167.4 and the low 164.5.
The difference between Lot # 69RH3 and 79YE22, being on average 2.45gr., while the difference between the highest and lowest cases in the 2 lots was 6.8gr.
For the .270, two boxes (40 cases) of lot #02YE31, averaged 186.7925 while lot # 4WH2 (10 cases) averaged 185.09gr.
The heaviest case in lot #02YE31 was, 189.3gr. while the lightest in lot #4WH2 is 184.4gr. giving a spread of 4.9 gr., lowest to highest.
The difference, on average, between these two lots #s is 1.7025gr.
AS said, this is probably not enough to cause any safety issues. However, in my load development situation with the Remington brass probably 20 years back, putting some odd lot cases into the testing mix DID cause greatly increased pressures!
WE are all cautioned to drop back and check for pressure/safety issues when we make a change in components and that fact also applies to changes in brands or lot numbers of cases.
So, it should go without saying, for the greatest consistance in our reloads, once a load has been established, buy a goodly amount of components, all from the same lot#.
I have seen sizable changes - 50 - 100fps - in velocity figures caused by the change of one lot number to another in powder, so beware.
Keep em coming!
Crusty Deary Ol'Coot
