Graham Smith Posted July 9, 2007 Share Posted July 9, 2007 Here is another typical newby question that probably comes up all the time. Why is there so much difference between different load tables for the same cartridge, bullet, and powder combination. I'm trying to work up a load for a 9x19 that will give me around 1100 fps using a Hornady 124 gr FP bullet and Titegroup powder. This is mainly an exercise I designed for the sake of understanding how all the different factors work together. But it's also because this weight and velocity are a good starting point for a load that will consistently make the minor power factor. What I am finding however is that the various references I have give vary different velocities for the same weight bullet and powder. I have checked the Lee, Hornady, Speer, and Hodgdon. Speer is several tenths of a grain lower for all bullet weights. Lee and Speer are closer, but Lee is referencing a 125 gr bullet. Hodgdon may be the best source since they make the powder. But, still and all, these are supposed to be rigorously tested and based on good solid numbers, so I wouldn't expect to see as much variation as I am seeing. Just in case the powder was the issue, I looked up the same load using several different powders including 231 and Unique which have been around forever. Same issue - numbers just don't come close to agreeing. What am I missing or should I just get it over with now and buy a chronograph and figure out my own load tables? Link to comment Share on other sites More sharing options...
.40AET Posted July 9, 2007 Share Posted July 9, 2007 What am I missing or should I just get it over with now and buy a chronograph and figure out my own load tables? You're not missing anything. None of them agree, some are close. They are nothing but a starting point for safe loads. There are so many different factors that effect the final velocity of a bullet that it would be next to impossible to get identical data. Wait until you change primer lots or powder lots and the load that you loved for a year is suddenly completely different. It's taxing at best, but stick with it. There are a lot of good sources of information here and shooters that can help. Good luck. Link to comment Share on other sites More sharing options...
G-ManBart Posted July 9, 2007 Share Posted July 9, 2007 Every test barrel is different just as every gun barrel is different. You can have to otherwise identical guns give you 50fps difference with the same ammo. Different lots of powder will give different results as well (some are more consistent than others). Check the barrel length the guide lists...some are going to be longer than others. Add those factors up, plus a bunch more and you're not going to get the same data twice. Definitely get the chronograph...can't go very far without one! Link to comment Share on other sites More sharing options...
Graham Smith Posted July 9, 2007 Author Share Posted July 9, 2007 Every test barrel is different just as every gun barrel is different. You can have to otherwise identical guns give you 50fps difference with the same ammo. Different lots of powder will give different results as well (some are more consistent than others). Check the barrel length the guide lists...some are going to be longer than others. Add those factors up, plus a bunch more and you're not going to get the same data twice. Definitely get the chronograph...can't go very far without one! All the charts I have looked at have been for a 4" barrel (I think) and most for a 1:10 twist, both of which are close to my G19. And I did expect some differences but I figured it would be a lot closer than this. <sheesh> Well, now it looks like I need to shopping for a chronograph and some place to set it up. I've been shooting at an indoor range which is out of the question for that. There are a couple "rod and gun" type clubs in the area that might allow this. At this rate, I'm going to have to shoot twice as much to save enough money to pay for all the equipment Link to comment Share on other sites More sharing options...
stingerjg Posted July 9, 2007 Share Posted July 9, 2007 At this rate, I'm going to have to shoot twice as much to save enough money to pay for all the equipment Reloading doesn't save money. It just lets you shoot twice as much for the same amount as buying loaded ammo. Link to comment Share on other sites More sharing options...
valkabit Posted July 9, 2007 Share Posted July 9, 2007 At this rate, I'm going to have to shoot twice as much to save enough money to pay for all the equipment Reloading doesn't save money. It just lets you shoot twice as much for the same amount as buying loaded ammo. It won't save you money, but it's fun. Link to comment Share on other sites More sharing options...
.40AET Posted July 9, 2007 Share Posted July 9, 2007 I've been shooting at an indoor range which is out of the question for that. Why? That's where I do all of my chrono work. A friend built a small dolly to roll the chrono out with and attached a PVC pipe to it. Roll it out 12 feet and start testing. I use an IR setup and it works great indoors. Link to comment Share on other sites More sharing options...
elenius Posted July 9, 2007 Share Posted July 9, 2007 Well, now it looks like I need to shopping for a chronograph and some place to set it up. I've been shooting at an indoor range which is out of the question for that. There are a couple "rod and gun" type clubs in the area that might allow this. One thing you could check before you buy one is whether your club has a loaner. I found out that mine does after I bought one. Then again, it's fun to have one The two clubs I checked do allow setting up a chrono in front of the shooting line. Shouldn't be a problem. Link to comment Share on other sites More sharing options...
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