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Posted: 11/5/2014 1:31:38 PM EDT
| Last weekend, I loaded 50 rounds of .45-70 using IMR-3031. I had 2 single pound cans in the cabinet. At 30 grains per round, one wasn't going to cover all 50, so I dumped part of the second can in the powder dispenser. The 2 cans had different lot numbers. Should I expect different performance from rounds with the different lot number? |
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IMO, lot to lot variations in todays commercial canister grade powders are small compared to bulk mil-surplus powders.
That being said, it's probably wise to back off a little and work up again when going to a different lot especially when rifle loads rather than pistol loads are concerned. For many years now I've loaded my pistol rounds with my same proven recipe without adjusting for new lots of powder. I'm playing the odds that consistency between lots is indeed held to higher standards for the commercial powders I use AND nearly every caliber I load for is rarely hotter than mid-range meaning any consistency issues probably aren't even noticed because of the "cushion" I keep between my chosen load and full on max. For rifle loads which run at considerably higher pressures, I always reduce and work back up. In your situation, I would've gotten a large container and mixed both bottles together to get the most homogeneous mixture between the two as possible. Edit: spelling |
| Retail powder should not be a problem as it is pretty consistent burn speed wise. Now if you buy it by the drum like I do getting it all from a single lot number is a bigger deal but it usually is not a problem. I have a powder I am using from 3 different lot numbers so I tested all 3 lots at one time and it is so close I will not make any adjustments from lot to lot, it is not always like this though. |
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Commercial smokeless powder is very close to identical lot to lot. That isn't to say that some difference may exist, Palma shooters found up to 1.0 whole grain difference to obtain the same velocity between various lots of Varget. These are maximum .308 loads shooting 155 grain SMK's. Some lots needed 46.0 grains, slower lots needed 47.0 grains.
If you aren't close to maximum you should be fine. If you are at or near maximum maybe not. |
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Quoted:
To me it all depends on the load. A moderate load, I will dump the next can of powder in the powder measure and keep going. For a load I have worked up to and consider max in my gun, I would drop back a grain or two and work back up. In 2009, a manufacturer's Ballistician (Johan Loubser) sent me an email stating that the maximum lot-to-lot propellant variation I could expect to see was 3%. This was done after I had seen/documented/reported a 3% lot-to-lot variation in a propellant. Some propellants have extremely good lot-to-lot consistency. Other propellants do not. Problem is you don't really know anything about a new lot's consistency until you fire that first round. Doing what dryflash3 recommends is smart reloading. |
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Quoted:
Last weekend, I loaded 50 rounds of .45-70 using IMR-3031. I had 2 single pound cans in the cabinet. At 30 grains per round, one wasn't going to cover all 50, so I dumped part of the second can in the powder dispenser. The 2 cans had different lot numbers. Should I expect different performance from rounds with the different lot number? Were these full? If so, one can should have been able to load well over 200 rounds. If they were not full,it's best to mix them together before dumping the powder into the dispenser. |
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If I didn't have any other loads needing the first lot as is I'd have mixed the two to blend it uniform, then work up. Two or three tablespoons of powder just get tossed into the new can and shook up, work up over the chrono for V. I haven't had anything too far off in years. Some ball powders back in the day made me wonder but now I am pretty sure it was mostly temp differences. (cool Spring versus hot Summer)
In the old days it was kind of nice to go back to the same gun shop and get a second can of powder from the same lot. Near impossible to do anymore. |
| If the lots were of recent vintage there is not likely to be much difference. If you have been using powder that is several years old, and have loads worked up with it, you might want to back off and work up your loads again for recently purchased powder, regardless of whether you mix the lots. Burn rate changes over time on stored powder in my experience, and manufacturers actually change burn rate slightly over time on the same powder number. I have see this especially with IMR and Hodgdon powders, less so with others. |
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Quoted:
Were these full? If so, one can should have been able to load well over 200 rounds. If they were not full,it's best to mix them together before dumping the powder into the dispenser. Quoted:
Quoted:
Last weekend, I loaded 50 rounds of .45-70 using IMR-3031. I had 2 single pound cans in the cabinet. At 30 grains per round, one wasn't going to cover all 50, so I dumped part of the second can in the powder dispenser. The 2 cans had different lot numbers. Should I expect different performance from rounds with the different lot number? Were these full? If so, one can should have been able to load well over 200 rounds. If they were not full,it's best to mix them together before dumping the powder into the dispenser. No. The first can was enough for 15 rounds. The second can was sealed. |
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