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  • Burn Rates

    Read a article recently discussing Burn Rates of smokeless powder. One comment he made is not all the charts are in agreement. I thought just the opposite - that all the test procedures were standardized.
    It used to be a sample of known weight and volume was put in a pressure bomb and the amount of gas.energy was measured as well as the combustion curve was plotted. Or, a sample was fired in a test barel with a pressure or strain gage to record results. I thought all that was SAMI standard. Aparently not. I have noticed as testing has become more accurate, the load max grains for Max charges have been reduced from those 50 years ago. As always, change anything and back down and work up. Believe in starting weights. Watch for changes in lot numbers.
    I have a lot of old powders and not experimeted with some of the new ones that make all kinds of accuracy, temp stability cleanleness, etc. Lots of things for new reloaders to look into. .

  • #2
    In general, the burn rate charts seem to be in about the right order. What is most important in reloading is that we use powders appropriate for the cartridge and bullet weights we are shooting. The reloading manuals are pretty good about that. I personally think that lawyers had more to do with taking the top off the Max Load in the manuals than did the burn rates.

    My biggest change related to this discussion of late have been to use more powders that are not as sensitive to changes in temperature. For example, I used to use IMR4350 and have now switched to H4350 and the Enduron powders so I have a better chance of using my favorite load all year long. I have also acquired a software load simulator called "Quick Load" to analyze a lot more great powders than I find in the various reloading manuals. It has been especially helpful in these times where I just can not acquire any of the powder I normally use.

    I also have come to favor the powders that help keep my barrel cleaner such as CFE223.

    Comment


    • #3
      Because of temperature sensitivity, I never load to maximum listed in the published load data except for the .357 Max and .45 Colt.

      My load development and testing is usually done from August to October in much higher temps than what I'll see hunting in December and January. If I'm going to run into overpressure it will be at the range and not in the field. But last summer I started keeping my ammo in a cooler at the range to mitigate the heating from 90+ air temps.

      Granted there could be a slight shift in point of impact from sighting in when it's warmer and then hunting when it's cooler. But like I've said, most of my shots are under 100 yards so it probably doesn't matter.

      Comment


      • #4
        Originally posted by DakotaMan View Post
        In general, the burn rate charts seem to be in about the right order. What is most important in reloading is that we use powders appropriate for the cartridge and bullet weights we are shooting. The reloading manuals are pretty good about that. I personally think that lawyers had more to do with taking the top off the Max Load in the manuals than did the burn rates.

        My biggest change related to this discussion of late have been to use more powders that are not as sensitive to changes in temperature. For example, I used to use IMR4350 and have now switched to H4350 and the Enduron powders so I have a better chance of using my favorite load all year long. I have also acquired a software load simulator called "Quick Load" to analyze a lot more great powders than I find in the various reloading manuals. It has been especially helpful in these times where I just can not acquire any of the powder I normally use.

        I also have come to favor the powders that help keep my barrel cleaner such as CFE223.
        I was wondering if the CFEreally helped.
        For chronographing loads in the summer I carry test loads to the range in a cooler with ice packs - simulate fall temps.

        Comment


        • #5
          Originally posted by jhjimbo View Post

          I was wondering if the CFEreally helped.
          For chronographing loads in the summer I carry test loads to the range in a cooler with ice packs - simulate fall temps.
          CFE does keep a barrel cleaner, making for more shooting between cleanings. Its main advantage is extra velocity for me though. In the hot summer sun, I also keep my cartridges in the shade. Letting them sit in 95 degree sun still jacks their velocity up significantly, even with the powders that are less sensitive to temperatures.

          In one outing, I inadvertently pulled a hundred rounds of 22-6mm Rem with RL22 out in 100 degree sun. By the time I got to the end of the box, my 500 yard holdover dot was right on at 750 yards.
          Last edited by DakotaMan; 07-25-2021, 08:34 PM.

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          • #6
            One thing to remember is that even when you are using a powder like H-4350, you can have lot to lot variations, and that is true of any brand of powder.

            Comment


            • #7
              Originally posted by Ernie View Post
              One thing to remember is that even when you are using a powder like H-4350, you can have lot to lot variations, and that is true of any brand of powder.
              I don;t propose anybody do this. When I get down to the last quarter pound and have the new powder in hand I pour both into a container and mix thoroughly. Been doing it for 40 years. By doing this I reduce any large variance in performance from lot to lot. The other thing is if the old can has been around a long time it has probably degraded a little in energy as aeromatic hydrocarbons have a tendency to evaporated off. A pound of new powder will replenish it somewhat and even out any difference in performance. Of course ONLY same powder from same manufacturer and always return to proper container. One other thing I do in prep to use powder is mix it up a little in the can as setteling may have heavier solvents and molecules gravitate to the bottom. Again, I do this but don't you do it..
              Last edited by jhjimbo; 07-27-2021, 04:42 PM.

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              • #8
                I think the only way to revisit load data from lot to lot is to shoot over a chronograph to get an idea of pressure. Pressure is relative to velocity and if the velocity changes much, you have a pressure change, not always a good thing. A chronograph is the shooters only tool to measure pressure changes. Most of the anecdotal pressure signs usually only appear north of 70,000 psi which is way over SAAMI max average pressure.

                Comment


                • #9
                  Originally posted by jhjimbo View Post

                  I don;t propose anybody do this. When I get down to the last quarter pound and have the new powder in hand I pour both into a container and mix thoroughly. Been doing it for 40 years. By doing this I reduce any large variance in performance from lot to lot. The other thing is if the old can has been around a long time it has probably degraded a little in energy as aeromatic hydrocarbons have a tendency to evaporated off. A pound of new powder will replenish it somewhat and even out any difference in performance. Of course ONLY same powder from same manufacturer and always return to proper container. One other thing I do in prep to use powder is mix it up a little in the can as setteling may have heavier solvents and molecules gravitate to the bottom. Again, I do this but don't you do it..
                  I’ll only mix the last quarter of a can with a new can IF IT IS FROM THE SAME LOT NUMBER to “average out” the moisture content. Otherwise, I never mix powders. Your mileage may vary.

                  Comment


                  • #10
                    Originally posted by WA Mtnhunter View Post
                    I’ll only mix the last quarter of a can with a new can IF IT IS FROM THE SAME LOT NUMBER to “average out” the moisture content. Otherwise, I never mix powders. Your mileage may vary.
                    Manufactures have a recipe outcome (pressure curve and total energy) for a type of powder, energy produced and burn curve. They adjust by adding components or adding things to retard burning rate to get to the final spec for that powder. So, even though two lots produce the same results, their components are not necessarily in the same proportion.

                    Comment


                    • #11
                      "... their components are not necessarily in the same proportion. ..."

                      All the more reason NOT to mix powders, regardless of amount.
                      There are 1750 grains in a quarter pound of powder. My heaviest load is 46 grains of IMR4895 in my .270 Win. As the powder level drops in my powder dump, I become more diligent in weighing charges so that I don't get a squib load.
                      I would toss out any remaining powder before I'd mix it.

                      BUT..... that's just me and that's how I would handle that situation.
                      To each his own.

                      Comment


                      • #12
                        I use a LabRadar on every shot possible and track the variance in powder lots. A couple weeks ago, on my competition 6mm Dasher, as I moved from one cannister of Varget powder to the next, my average velocity dropped from 2970 to 2948 and of course my 600 yard precision was terrible. I just had to make charge adjustments to get back to 2970... no big deal. I've always threatened to dump all the lots I have in one bucket and mix them but I never have. Such a great variance is actually pretty rare and even then, it is easy to deal with.

                        Comment


                        • #13
                          I must be doing it wrong. I develop a hunting load and use it, ignoring temperature sensitivity and lot variations. And yes, I'll mix the last portion of one can with a new one of the same powder type, totally ignoring the lot number. Never had an impact shift from powder variations to make me miss a deer or pig.
                          Last edited by PigHunter; 07-28-2021, 11:40 AM.

                          Comment


                          • #14
                            Originally posted by FirstBubba View Post
                            "... their components are not necessarily in the same proportion. ..."

                            All the more reason NOT to mix powders, regardless of amount.
                            There are 1750 grains in a quarter pound of powder. My heaviest load is 46 grains of IMR4895 in my .270 Win. As the powder level drops in my powder dump, I become more diligent in weighing charges so that I don't get a squib load.
                            I would toss out any remaining powder before I'd mix it.

                            BUT..... that's just me and that's how I would handle that situation.
                            To each his own.
                            my RCBS powder drop has a baffel so the weight of the powder in tube does not affect dispensed weight. don't use it any more - gone electric balance all the way and now have elec dispenser accurate to .1gr. my other balance is accurate to .oo1gr. RCBS is too sensitive to operator consistency. actually when i first got it sent it to RCBS because i thought it was defective - they said it was good. it would throw way too inaccurate for me, especially with small charges, even with small hole cylender. checking with a beam balance is better than relying on dispenser.

                            Comment


                            • #15
                              Originally posted by PigHunter View Post
                              I must be doing it wrong. I develop a hunting load and use it, ignoring temperature sensitivity and lot variations. And yes, I'll mix the last portion of one can with a new one of the same powder type, totally ignoring the lot number. Never had an impact shift from powder variations to make me miss a deer or pig.
                              You are not doing it wrong for what you are doing.
                              For hunting at what many would say is normal distances, the issues that are being discussed are a non-issue.
                              The only thing that might pertain, is if you are running the ragged edge of high pressure, and you get into a lot of powder that jumps pressure even higher.
                              Don't worry about it and enjoy yourself

                              Comment

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