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Old November 12, 2009, 09:45 PM   #1
craig2724
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Chronograph results for 9mm loads

I just checked 2 loads for my Springfield XD 9mm with a 4" barrel.

125 grain lead bullet, Mastercaster Bullet
3.4 grains of 700X
COL: 1.120
950 FPS average
The variation in 3 shots was 20 fps.

115 grain copper plated, Berry's
3.9 grains of 700X
COL: 1.110
1100 fps average
The variation in 3 shots was 50 fps.

These both work very well and I have not seen any signs of leading from the Mastercast Bullets. I would recommend them to anybody.
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Old November 13, 2009, 12:43 AM   #2
rc
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If you bump up your powder charges a bit, you should see your extreme spread tighten as you get a more efficient burn at slightly higher pressure.
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Old November 13, 2009, 04:01 AM   #3
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Hard to tell what the variation is now? 3 shots is not statistically significant. The first load could still have more variation than the first, but three shots just randomly didn't happen to show it. Harder crimps will tend to improve it. Some find that seating primers extra firmly improves consistency, though that is most likely just a way of insuring no inadequately seated primers are present. Higher charge cut into it, too, but if you are after a target velocity load, you likely don't want that. Going to an even faster powder can get you the same thing.
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Old November 13, 2009, 07:02 AM   #4
craig2724
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I understand that 3 shot isn't significant but I didn't have time to shoot 30 shots. I am new to reloading and I am not sure what kind of velocity variation is normal, 10 fps, 20, 30, ...?

The cases are fairly new, shot 2 or 3 times, but I don't measure the case length prior to loading. How much of an impact would that make? I have also been told that if I seat a little bit deeper that the pressure will increase and possible be more consistant.
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Old November 25, 2009, 09:35 AM   #5
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Sorry I didn't spot your reply sooner.

Seating deeper tends to increase pressure, but some bullets, particularly lubricated lead, can be driven forward by the primer, increasing the space before the powder really gets burning, so sometimes the practice produces more erratic results, too.

I like to seat the lead and plated bullets out far enough to touch down on the rifling of the barrel. That improves start pressure consistency, but some bullet shapes stick out too far to feed when you do that. You'll have to try it with your bullets to see? In general, it improves accuracy and reduces leading.

Long range rifle shooters, form whom velocity consistency is most critical, try to get their standard deviation under 10 fps out of 2500 to 3500 fps MV. Pretty tight. For pistol you will find 50 fps extreme spread is pretty common. Shorter barrels are worse, and I've seen 150 fps E.S. in snub nose guns, which is 25% of the MV for some of them. Too much. Faster powder helps to cut that down. Crimping hard can help quite a bit, and that's another thing you can do when you are headspacing on the bullet touching the throat rather than on the case neck itself.

Case length is not an issue except as it affect crimping pressure. Have the cases the same length improves crimp consistency. The powder cares about the space it starts burning in, and if two cases are identical except for the length, then two bullets seated to the same COL will have the same powder space, regardless of where the case mouth is on the bullet.
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